All Publications

@article{vanschijndel2026,

title = {Feasibility and Accuracy of Body-Fat Assessment Using Standardized Skinfold-Thickness Assessment Versus Dual-Energy X-Ray Absorptiometry in Paralympic Athletes},

author = {Nick Van Schijndel and Vera Weijer and Luc J. C. Van Loon and Jan-Willem Van Dijk},

doi = {10.1123/ijspp.2025-0284},

issn = {1555-0265},

year  = {2026},

date = {2026-02-01},

journal = {International Journal of Sports Physiology and Performance},

volume = {21},

number = {2},

pages = {241–251},

abstract = {Purpose: To evaluate the feasibility and accuracy of body-fat assessment using standardized skinfold-thickness assessment versus dual-energy X-ray absorptiometry (DXA) in Paralympic athletes. Method: In this cross-sectional study, body composition was assessed in 49 male and female Paralympic athletes (Para cycling, Para skiing, Para swimming, wheelchair basketball, and wheelchair tennis) by a whole-body DXA scan and skinfold-thickness measurements conducted according to International Society for the Advancement of Kinanthropometry (ISAK) standards. Correlation and Bland–Altman analyses were conducted to compare both methods. Results: DXA was feasible in all athletes, while the sums of 4, 7, and 8 skinfolds were obtained in 88%, 73%, and 73% of the athletes, respectively. Median DXA-derived body-fat percentage was 16.3% (13.4%–20.5%) in males and 27.8% (21.1%–33.4%) in females. Strong correlations were found between DXA-derived body-fat percentage and the sum of 4 (r = .85), 7 (r = .83), and 8 (r = .83) skinfolds. However, skinfold-based prediction equations for estimating body-fat percentage were associated with substantial negative bias (-2.0% to -7.9%) and large individual error compared with DXA. Conclusion: DXA is a feasible method for assessing body composition in Paralympic athletes, while ISAK skinfold measurements face some challenges due to disability-related landmarking issues. Despite these limitations, skinfold thickness remains strongly associated with DXA-derived body fat. It is recommended to measure all skinfolds that can be reliably obtained according to ISAK standards and interpret them as a cumulative ``sum of feasible sites,'' rather than enforcing a universal skinfold metric across all Paralympic athletes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Trommelen2026,

title = {Daily Myofibrillar Protein Synthesis Rates Do Not Differ During Interval Compared to Continuous Exercise Training Matched for Duration and Work in Healthy Young Men},

author = {Jorn Trommelen and Martin J. MacInnis and Joshua P. Nederveen and Jean Nyakayiru and Bryon R. McKay and Sara Y. Oikawa and Joy P.B. Goessens and Dinesh Kumbhare and Gianni Parise and Stuart M. Phillips and Martin J. Gibala and Luc J.C. van Loon},

doi = {10.1123/ijsnem.2025-0074},

issn = {1543-2742},

year  = {2026},

date = {2026-01-01},

urldate = {2026-01-01},

journal = {International Journal of Sport Nutrition and Exercise Metabolism},

volume = {36},

number = {1},

pages = {13--20},

publisher = {Human Kinetics},

abstract = {<jats:p>

                    High-intensity interval training (HIIT) may elicit different skeletal muscle responses compared to work-matched moderate-intensity continuous training (MICT). The effect of work-matched HIIT versus MICT on myofibrillar protein synthesis remains to be determined. In the present study, we assessed the effect of short-term HIIT versus MICT on myofibrillar protein synthesis rates using a single-leg within-participant design. Ten healthy young men (age: 20 ± 1 years) performed six to eight training sessions with each leg over 2 weeks while ingesting deuterated water to assess myofibrillar protein synthesis. One leg was randomly assigned to perform HIIT and the other MICT. Skeletal muscle biopsies were collected at rest from one leg before and after a 2-week habituation period and from both legs after the training period to assess myofibrillar protein synthesis rates. HIIT and MICT increased single-leg maximal power output (main effect,

                    <jats:italic>p</jats:italic>

                     < .01), with no differences between legs (interaction:

                    <jats:italic>p</jats:italic>

                     = .61). Myofibrillar protein synthesis rates did not differ between the habituation period, MICT, or HIIT (1.39 ± 0.16%, 1.24 ± 0.30%, and 1.42 ± 0.31% per day, respectively;

                    <jats:italic>p</jats:italic>

                     = .29). In conclusion, we observed no detectable differences in daily myofibrillar protein synthesis rates between HIIT or work-matched MICT when assessed over a 2-week exercise training period in recreationally active young adult men.

                  </jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{domic2025b,

title = {The Effect of a Vegan Diet with or without Resistance Exercise on Thigh Muscle Volume in Older Adults. Research Protocol of the Vold-study: A 12-Week Randomized Controlled Trial},

author = {Jacintha Domic and Pol Grootswagers and Philippe Jm Pinckaers and Inge Groenendijk and Josep Rubert and Luc Jc Van Loon and Lisette C. P. G. M. Groot},

doi = {10.1186/s12877-025-06708-9},

issn = {1471-2318},

year  = {2025},

date = {2025-12-01},

journal = {BMC Geriatrics},

volume = {26},

number = {1},

abstract = {BackgroundPlant-based diets are increasingly adopted. Plant-based foods exhibit a lower protein quantity and quality compared to animal-based foods. As such, a fully plant-based, i.e. vegan, diet may be suboptimal for the maintenance of skeletal muscle mass later in life. The primary objectives of this study protocol are therefore: (1) To assess the effect of a 12-week self-composed vegan diet in comparison to an omnivorous diet on thigh muscle volume in community-dwelling older adults; and (2) To assess the effect of a 12-week self-composed vegan diet combined with twice-weekly resistance exercise (RE) on thigh muscle volume in comparison to a vegan diet without RE in community-dwelling older adults.MethodsSeventy-two community-dwelling individuals aged $>$= 65 years with a BMI between 23 and 32 kg/m2 will be included in this randomized controlled trial. Eligible participants will be randomly allocated to either follow their habitual omnivorous diet, a self-composed vegan diet, or a self-composed vegan diet combined with two sessions of RE per week for 12 weeks. Participants will be guided through monthly nutrition information meetings. Dietary intake and physical activity levels will be assessed using food records and accelerometery. The primary study outcome will be thigh muscle volume, assessed at baseline and after 12 weeks using magnetic resonance imaging (MRI). Secondary outcomes will be: body composition, muscle fat infiltration, muscle strength, bone mineral density, bone turnover markers, metabolic profile, insulin levels, cobalamin, iron and vitamin D status, hs-CRP, gut metabolomics and metagenomics, gastro-intestinal symptoms and dietary intake. Measurements will take place at baseline, after 6 weeks, and after 12 weeks. Additionally, mixed muscle protein synthesis rates will be assessed during the first ten days of the intervention using a deuterium oxide protocol. Data will be analysed using independent t-tests and linear mixed models.DiscussionThe results will provide valuable insights regarding the implications of consuming a vegan diet later in life for skeletal muscle and other health outcomes, and may contribute to the substantiation of the envisaged more plant-based dietary guidelines.Trial registrationThe trial is registered at clinicaltrials.gov (NCT05809466; registered on 22 February 2023).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{monsegue2025,

title = {Aerobic Exercise Training Improves Blood Glucose Homeostasis in Healthy Older Adults},

author = {Alejandra P. Monsegue and Milan W. Betz and Hasibe Aydeniz and Wendy E. Sluijsmans and Luc J. C. Van Loon and Tim Snijders and Lex B. Verdijk},

doi = {10.1016/j.exger.2025.112940},

issn = {0531-5565},

year  = {2025},

date = {2025-12-01},

journal = {Experimental Gerontology},

volume = {212},

number = {112940},

abstract = {The present study assessed the effects of aerobic exercise training (AER) on blood glucose regulation in healthy older adults, and whether these effects depend on baseline glucose regulation. Thirty-four healthy older adults (71~± ~4 y) were randomized to perform 8~weeks of AER (n~=~17) or no exercise (CON, n~=~17). A five-point oral glucose tolerance test was performed at baseline and post-intervention to assess plasma glucose and insulin concentrations. Glucose regulation was assessed by Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), Hepatic Insulin Resistance Index (HIRI), Muscle Insulin Sensitivity Index (MISI), and Matsuda index. Two-factor repeated measures ANOVAs were performed on the full cohort and on a subgroup (CON: n~=~10, AER: n~=~9) with Matsuda index $łeq$5. Full Cohort Analyses: a significant interaction effect (P~$<~$0.05) was observed only for HIRI (P~=~0.025), which worsened in CON (+151~± ~232, P~=~0.016) but not AER (-32~± ~221, P~=~0.557). Subgroup Analyses: significant interaction effects were observed for hepatic glucose regulation (P~$łeq~$0.013), which worsened in CON (HOMA-IR: +0.5~± ~0.6, P~=~0.085; HIRI: +249~± ~253, P~=~0.006), but tended to improve in AER (HOMA-IR: -0.6~± ~1.2, P~=~0.051; HIRI: -133~± ~241, P~=~0.125). A significant interaction effect was observed for Matsuda index (P~=~0.004), which increased in AER (from 3.2~± ~1.1 to 4.8~± ~2.1, P~=~0.002), but remained unchanged in CON (from 3.8~± ~0.9 to 3.5~± ~1.4, P~=~0.401). A trend toward an interaction effect was noted for MISI (AER: from 0.12~± ~0.07 to 0.19~± ~0.16; CON: from 0.18~± ~0.11 to 0.16~± ~0.06, P~=~0.082). Aerobic exercise training improves blood glucose regulation in healthy older adults, with greater impact in those with a more compromised blood glucose regulation (based on Matsuda index $łeq$5).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{boot2025a,

title = {Ingestion of 20 g Whey or Canola Protein Does Not Further Increase Muscle Protein Synthesis Rates During Recovery From Resistance Exercise In Healthy, Young Females},

author = {Noortje Boot and Wesley JH Hermans and Lisa ME Kuin and Julia M. Malowany and Floris K. Hendriks and Ines Warnke and Joan M. Senden and Alex Overman and Joy PB Goessens and Antoine Zorenc and Esther Kornips and Lex B. Verdijk and Luc JC Loon},

doi = {10.1016/j.tjnut.2025.10.018},

issn = {0022-3166},

year  = {2025},

date = {2025-12-01},

journal = {Journal of Nutrition},

volume = {155},

number = {12},

pages = {4123–4135},

abstract = {Background: Protein ingestion during recovery from exercise can further increase muscle protein synthesis rates. Plant-derived proteins are generally believed to have lesser anabolic properties than animal-derived proteins. To our knowledge, no studies have compared the impact of plant-derived with that of animal-derived protein ingestion on postexercise muscle protein synthesis rates in healthy, young females. Objectives: This study compared muscle protein synthesis rates following the ingestion of 20 g native canola protein, 20 g whey protein, or a noncaloric placebo during recovery from a single bout of resistance exercise in healthy, young females. Methods: In this randomly assigned, parallel group, double-blind placebo-controlled design, 36 healthy young (age, 23 ± 4 y; BMI, 22.7 ± 2.2 kg/m 2) females performed 8 sets of lower-body resistance exercise at 80% of their predetermined 1-repetition maximum after which they ingested 20 g native canola protein isolate, 20 g whey protein isolate, or a noncaloric placebo. Primed continuous L-[ring- 13C 6]-phenylalanine infusions were applied with frequent sampling of blood and muscle tissue to assess postprandial plasma amino acid profiles and 5-h postexercise muscle protein synthesis rates. Data are presented as mean ± SD. Results: Plasma essential amino acid concentrations strongly increased following ingestion of both whey and canola protein when compared with the placebo treatment (peak: 2113 ± 354, 1249 ± 173, and 780 ± 60 μmol/L, respectively; P $<$ 0.001) with greater postprandial plasma essential amino acid availability following whey than after canola protein ingestion (incremental AUC, 158 ± 50 and 90 ± 23 mmol/L × 5 h; P $<$ 0.001). No significant differences in postexercise muscle protein synthesis rates were observed following the ingestion of whey protein isolate, canola protein isolate, and placebo (0.071 ± 0.015, 0.069 ± 0.016, and 0.061 ± 0.013%/h, respectively; treatment; P = 0.200). Conclusions: A single session of resistance exercise strongly increases muscle protein synthesis rates in young females. Ingestion of 20 g whey or native canola protein does not further augment muscle protein synthesis rates during the early stages of postexercise recovery in healthy, young females. This trial was registered at clinicaltrials.gov as NCT05664269.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{fuchs2025d,

title = {Breakfast Consumption Does Not Rapidly Increase Liver or Muscle Glycogen Content in Well-Trained Cyclists},

author = {Cas J. Fuchs and Pandichelvam Veeraiah and Wesley J. H. Hermans and Bente Brauwers and Rick Voncken and Jorg Van Beek and Kim Brouwers and Job Van Den Hurk and Peter E. Thelwall and Jeanine J. Prompers and Luc J. C. Van Loon},

doi = {10.1152/ajpendo.00400.2025},

issn = {0193-1849},

year  = {2025},

date = {2025-11-01},

journal = {American Journal of Physiology : Endocrinology and Metabolism},

volume = {329},

number = {5},

pages = {E774-E780},

abstract = {A carbohydrate-rich breakfast is commonly consumed by cyclists to compensate for an overnight decline in liver glycogen content and, as such, to maximize liver glycogen stores in the hours before exercise. However, the extent to which liver glycogen content increases in response to the intake of a carbohydrate-rich breakfast in well-trained cyclists remains unexplored. Twelve well-trained male cyclists (age: 25 +/- 5 yr; Vo(2peak): 67 +/- 5 mLmin(-1)kg(-1); W-max: 5.8 +/- 0.7 Wkg(-1)) participated in this trial. Carbon-13 magnetic resonance spectroscopy (C-13-MRS) at 7 T and magnetic resonance imaging (MRI) at 3 T were applied to assess muscle and liver glycogen concentrations and volume, respectively, before and 3 h after ingesting a carbohydrate-rich breakfast providing 3 g carbohydrates per kg body mass. Following breakfast ingestion, muscle glycogen concentrations, muscle volumes, and total muscle glycogen content did not change (P $>$ 0.05). Liver glycogen concentrations increased by similar to 10% (from 164 +/- 30 to 180 +/- 33 mmol/L; P = 0.036), whereas liver volumes decreased by similar to 6% (from 1.96 +/- 0.28 to 1.84 +/- 0.27 L; P $<$ 0.001) in the 3 h following breakfast ingestion. Consequently, no net change in overall liver glycogen content was observed following breakfast ingestion (from 53 +/- 15 to 54 +/- 13 g; P = 0.516). Ingesting a carbohydrate-rich breakfast (providing 3 g carbohydrates per kg body mass) does not elevate liver or muscle glycogen content during the subsequent 3-h postprandial period.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{boot2025,

title = {Evaluation of Processing of Canola Protein Isolate on Postprandial Plasma Amino Acid Profiles in Healthy, Young Females},

author = {Noortje Boot and Wesley J. H. Hermans and Ines Warnke and Alex Overman and Janneau M. X. Kranenburg and Joan M. Senden and Lex B. Verdijk and Luc J. C. Loon},

doi = {10.1007/s00726-025-03482-1},

issn = {0939-4451},

year  = {2025},

date = {2025-10-01},

journal = {Amino Acids},

volume = {57},

number = {1},

abstract = {Canola protein is a rapeseed-derived protein that contains all essential amino acids in proportions that meet the WHO amino acid scoring requirements, making it an interesting protein for human food applications. It is currently unknown whether canola protein processing modulates postprandial plasma amino acid bioavailability in vivo in humans. This study compared postprandial plasma amino acid profiles following the ingestion of unprocessed (native) canola, processed canola, and whey protein isolate in healthy, young, females. In a randomized, clinical, cross-over design, 15 healthy young females (25 +/- 3 y) participated in four test days on which they consumed 20 g protein as either native canola, enzyme processed or heat processed canola protein, or 20 g whey protein. Blood samples were collected for 5 h following protein ingestion to assess plasma amino acid concentrations. Ingestion of native canola protein resulted in lower increases in plasma total amino acid (TAA) concentrations compared to whey protein (3191 +/- 794 vs. 4429 +/- 84 mu mol center dot L- 1, P $<$ 0.001). Canola protein processing resulted in greater peak plasma total amino acids concentrations, reaching statistical significance for enzyme (3599 +/- 687 mol center dot L- 1},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{fuchs2025c,

title = {Carbohydrate Intake of 10 g/Kg Body Mass Rapidly Replenishes Liver, but Not Muscle Glycogen Contents, during 12 h of Post-Exercise Recovery in Well-Trained Cyclists},

author = {Cas J. Fuchs and Pandichelvam Veeraiah and Wesley J. H. Hermans and Bente Brauwers and Rick Voncken and Kim Brouwers and Heather L. Petrick and Floris K. Hendriks and Julia L. M. Bels and Job Hurk and Jil Weber and Joan M. Senden and Fiona E. Smith and Peter E. Thelwall and Jeanine J. Prompers and Luc J. C. Loon},

url = {https://www.scopus.com/pages/publications/105013783311},

doi = {10.1113/JP289115},

issn = {0022-3751},

year  = {2025},

date = {2025-08-01},

urldate = {2025-09-12},

journal = {Journal of Physiology},

abstract = {Post-exercise carbohydrate intake is required to replenish endogenous glycogen stores. Although adequate carbohydrate consumption has been reported to restore muscle glycogen contents within 24 h of post-exercise recovery, the time required to replenish liver glycogen contents is less evident. Twelve well-trained male cyclists (age: 25 +/- 5 years; V O(2)peak: 67 +/- 5 ml/min/kg; W-max: 5.8 +/- 0.7 W/kg) participated in this trial. Ultra-high-field (UHF) C-13 magnetic resonance spectroscopy (C-13 MRS) was applied to assess muscle and liver glycogen concentrations before and immediately after glycogen-depleting exercise on two test days. This was followed by 12 h of recovery during which participants remained fasted (CON) or consumed 10 g carbohydrate per kg body mass (BM) in the form of sucrose-containing beverages (1.2 g/kg BM/h over the first 6 h) and carbohydrate-rich meals (CHO). Muscle and liver glycogen concentrations were again assessed at 6 and 12 h into recovery using C-13 MRS. Furthermore muscle biopsies were collected to assess muscle glycogen concentrations using biochemical analysis. Exercise significantly reduced muscle (from 159 +/- 32 to 56 +/- 19 mmol/l; -64%) and liver (from 166 +/- 40 to 110 +/- 44 mmol/l; -34%) glycogen concentrations (P $<$ 0.05), with no significant differences between test days (P $>$ 0.05). In the absence of carbohydrate intake (CON) muscle and liver glycogen concentrations remained unchanged during recovery. After carbohydrate intake (CHO) muscle glycogen concentrations increased from 56 +/- 19 to 88 +/- 16 and 110 +/- 19 mmol/l (or from 269 +/- 90 to 418 +/- 78 and 523 +/- 92 in mmol/kg dry mass), after 0, 6 and 12 h of recovery, respectively, remaining well below pre-exercise values (i.e. 55% of pre-exercise at 6 h and 69% at 12 h). Liver glycogen concentrations increased from 110 +/- 44 to 236 +/- 39 and 258 +/- 40 mmol/l, after 0, 6 and 12 h of recovery, respectively, exceeding pre-exercise values within 6 h of recovery (i.e. 142% of pre-exercise). A very strong correlation (r = 0.89, P $<$ 0.001), good agreement (ICC: 0.87) and low bias (4.1 +/- 23.7 mmol/l) were observed when comparing muscle glycogen concentrations assessed using 13C MRS and biochemical analyses. Sucrose ingestion (1.2 g/kg BM/h) fully restored liver glycogen concentrations well within 6 h of post-exercise recovery. Ingesting large amounts of carbohydrate (10 g/kg BM) did not allow muscle glycogen stores to be replenished within 12 h of post-exercise recovery.Key points Carbohydrate ingestion is required to replenish muscle and liver glycogen stores after a strenuous bout of exercise. Carbon-13 magnetic resonance spectroscopy at ultra-high-field (7T) allows non-invasive measurement of both muscle and liver glycogen contents before and after exercise, and at 6 and 12 h of recovery with (CHO) and without (CON) carbohydrate ingestion (10 g per kg body mass). Exercise strongly reduces glycogen contents of both muscle and liver tissue. Without carbohydrate ingestion muscle and liver glycogen levels remain depleted. After ingestion of large amounts of carbohydrate both muscle and liver glycogen contents increase rapidly, with liver glycogen stores being fully repleted within 6 h. Ample carbohydrate ingestion allows rapid replenishment of liver but not muscle glycogen stores within 6 and 12 h of post-exercise recovery.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{fuchs2025b,

title = {Muscle Preservation during Hospitalization: Energy Balance, Protein Intake, and Habitual Physical Activity},

author = {Cas J Fuchs and Luc J C Loon},

doi = {10.1097/MCO.0000000000001154},

issn = {1363-1950},

year  = {2025},

date = {2025-08-01},

journal = {Current Opinion in Clinical Nutrition and Metabolic Care},

abstract = {PURPOSE OF REVIEW: Muscle loss during hospitalization is a major clinical concern, as it has been associated with reduced physical function, quality of life, and increased mortality. This review outlines the key causes of muscle wasting and highlights practical strategies to support muscle mass preservation during hospitalization. RECENT FINDINGS: Physical inactivity, along with reduced energy and protein intake, are the primary drivers of muscle atrophy during hospitalization by suppressing muscle protein synthesis (MPS). Maintaining energy balance is critical to prevent declines in MPS rates and attenuate muscle loss. Preserving habitual protein intake is essential and, when total energy intake is reduced, should be achieved through a more protein-dense diet. Preventing disuse atrophy requires at least some level of daily physical activity. Physical activity sensitizes skeletal muscle to the anabolic properties of protein ingestion, enabling greater use of protein-derived amino acids for MPS. Therefore, frequent in-hospital movements, such as bed-to-chair transfers and walking, should be encouraged. When voluntary activity or muscle contractions are impossible, exercise mimetics, like neuromuscular electrical stimulation, may be applied to stimulate muscle activity and limit muscle mass loss. SUMMARY: Preserving muscle mass during hospitalization requires a multimodal approach: achieving energy balance, maintaining protein intake, minimizing muscle disuse, and, whenever necessary, apply exercise mimetics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{domic2025,

title = {The Amino Acid Composition of Commercially Available Vegan Meat and Dairy Analogues},

author = {Jacintha Domic and Luc Jc Loon and Els Siebelink and Karin J Borgonjen-van den Berg and Lisette Cpgm Groot and Pol Grootswagers},

url = {https://www.scopus.com/pages/publications/105012361022},

doi = {10.1017/S000711452510408X},

issn = {0007-1145},

year  = {2025},

date = {2025-07-01},

urldate = {2025-09-15},

journal = {British Journal of Nutrition},

pages = {1–31},

abstract = {Plant-based meat and dairy analogues contain less protein than their animal-based counterparts and rely on various plant protein sources, which frequently display incomplete amino acid (AA) profiles that do not reflect dietary requirements due to low quantities of one or more essential AA (EAA). There is little insight in the AA profiles of most of these plant-based analogues. We assessed the AA composition of 40 plant-based meat and dairy analogues that were commercially available in The Netherlands in March 2023, and compared their EAA profile to dietary requirements and to the EAA profile of their meat and dairy counterparts. Total protein contents were lower in most analogues when compared to their animal-based counterparts (meat analogues, = 16 (80%); lunch meats and cheese analogues, = 10 (100%); milk and yoghurt analogues, = 9 (90%)) and accompanied by lower EAA contents. In reference to dietary requirements, the sum of the total EAA contents was adequate in all but one of the analogues. Nevertheless, all analogues displayed deficiencies in one or more specific EAA. Methionine contents were most frequently low ( = 39; 98%), followed by lysine contents ( = 11; 28%). Essential AA compositions varied between analogues irrespective of the protein source(s) used. In conclusion, plant-based meat and dairy analogues exhibit incomplete EAA profiles, which may compromise adequate protein nutrition in plant-centered diets.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{holwerda2025,

title = {Assessing the Composition of Myofibrillar and Muscle Connective Protein Fractions within Skeletal Muscle Tissue},

author = {Andrew M Holwerda and Thorben Aussieker and Joan Senden and Freek G Bouwman and Janneau Kranenburg and Alexander Overman and Tim Snijders and Lex B Verdijk and Lars Holm and Luc J C Loon},

doi = {10.1080/10408398.2025.2522363},

issn = {1040-8398},

year  = {2025},

date = {2025-06-01},

journal = {Critical Reviews in Food Science and Nutrition},

pages = {1–12},

abstract = {(195 WORDS)It has been suggested that different nutritional stimuli are required to augment myofibrillar versus muscle connective protein synthesis rates. To study such different aspects of skeletal muscle remodeling, researchers often isolate myofibrillar or connective protein fractions from muscle tissue samples. However, the composition of these muscle protein fractions remains poorly defined. Here, we evaluated the amino acid profiles and protein compositions of the myofibrillar and muscle connective protein fractions within skeletal muscle tissue. The muscle connective protein fraction was shown to contain textasciitilde70% of the total mixed muscle collagen content, with 4.4 ± 0.9% collagen relative to total protein content. This was 3-4 fold greater than the collagen content in mixed muscle tissue (1.2 ± 0.2%; $<$ 0.05). Myofibrillar proteins, such as actin and myosin, accounted for 39% of the myofibrillar protein fraction and 32% of the muscle connective protein fraction. The muscle connective protein fraction contained a higher proportion (42%) of key scaffolding proteins compared to the myofibrillar protein fraction (11%). In conclusion, the muscle connective protein fraction contains an enriched proportion of collagen among a large proportion of intra- and extracellular scaffolding and cell adhesion proteins, all of which are far less abundant in the myofibrillar protein fraction.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{vanlieshout2025a,

title = {Milk Protein Glycation Compromises Postprandial Lysine Bioavailability but Does Not Modulate Postprandial Muscle Protein Synthesis Rates In Vivo in Males: A Double-blind, Randomized Parallel Trial},

author = {Glenn Aa Lieshout and Jorn Trommelen and Floris K Hendriks and Jean Nyakayiru and Janneau Kranenburg and Joan M Senden and Joy Pb Goessens and Lex B Verdijk and Marjolijn Ce Bragt and Luc Jc Loon},

doi = {10.1016/j.tjnut.2025.05.032},

issn = {0022-3166},

year  = {2025},

date = {2025-05-01},

journal = {Journal of Nutrition},

abstract = {BACKGROUND: Industrial processing and storage of milk products can strongly increase protein glycation concentration. Previously, we have reported that a high protein glycation concentration impairs protein digestion, thereby compromising lysine bioavailability. The lower postprandial lysine availability may restrict the anabolic properties of a high glycated protein. OBJECTIVES: The objective of this study was to assess the impact of milk protein glycation on postprandial plasma amino acid availability and subsequent postprandial muscle protein synthesis rates during recovery from a single bout of resistance-type exercise. METHODS: Forty-five recreationally active, healthy young males participated in this double-blinded, randomized parallel study. After performing a single bout of whole-body resistance-type exercise, subjects ingested 20 g milk protein with either a low (4%; LOW-GLYC) or high (47%; HIGH-GLYC) glycation concentration or a noncaloric placebo (PLA). Continuous intravenous infusion of L-[ring- C ]-phenylalanine was combined with the collection of blood and muscle tissue samples during a 6-h postprandial period to assess plasma amino acid concentrations and muscle protein synthesis rates. RESULTS: Protein ingestion increased plasma total and essential amino acid concentrations compared with placebo (time × treatment interaction: P $<$ 0.001), with no differences between the low and high glycated milk protein. Plasma lysine availability, assessed over the full 6 h postprandial period, was substantially lower following ingestion of the protein with the high compared with low glycation concentration (-5 ± 7 compared with 10 ± 9 mmol$cdot$L $cdot$360 min, respectively, P $<$ 0.001). Postprandial muscle protein synthesis rates did not differ between treatments (0.059 ± 0.016, 0.061 ± 0.012, and 0.061 ± 0.018 %×h , in LOW-GLYC, HIGH-GLYC and PLA, respectively},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{cuijpers2025,

title = {Nutritional Strategies Targeting Age-Related Skeletal Muscle Fibrosis: Underlying Mechanisms},

author = {Iris Cuijpers and Joey Katsburg and Luc J C Loon and Freddy J Troost and Mireille M J P E Sthijns},

doi = {10.1080/10408398.2025.2498676},

issn = {1040-8398},

year  = {2025},

date = {2025-05-01},

journal = {Critical Reviews in Food Science and Nutrition},

pages = {1–21},

abstract = {Aging is associated with a reduced number and function of muscle stem cells (MuSC). This results in a decreased muscle regenerative capacity and increased formation of fibrotic tissue, impairing skeletal muscle function. This review provides an overview of and animal studies investigating nutritional interventions with the potential to inhibit pathophysiological mechanisms involved in the development of skeletal muscle fibrosis. Mechanism targets include 1) MuSC function and myogenic differentiation, 2) M1 to M2 macrophage polarization, 3) myofibroblast activity or extracellular matrix (ECM) deposition, and 4) reactive oxygen species (ROS) mediated pathways, such as NOX2/4 activity. Most promising nutrients described in this review are phytonutrients, vitamins and amino acids. Quercetin targets multiple pathways (showing decreased inflammation, ECM expression and NOX2/4 activity) in various cell types and tissues (kidney, aorta, liver and (heart) muscle) of rodents and rabbits, which could contribute to fibrosis development. Additionally, sulforaphane is a promising candidate as it inhibits inflammation, ECM expression, and ROS production in mouse skeletal muscle. After validation of the effects in human skeletal muscle, supplementation with these nutrients could be implemented in a multifaceted intervention (including exercise and adequate protein intake) targeting age-related skeletal muscle fibrosis.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{korzepa2025a,

title = {Resistance Training Increases Myofibrillar Protein Synthesis in Middle-to-Older Aged Adults Consuming a Typical Diet with No Influence of Protein Source: A Randomized Controlled Trial},

author = {Marie Korzepa and Jonathan I Quinlan and Ryan N Marshall and Lucy M Rogers and Archie E Belfield and Yasir S Elhassan and Alex Lawson and Chloe Ayre and Joan M Senden and Joy Pb Goessens and Elisa I Glover and Gareth A Wallis and Luc Jc Loon and Leigh Breen},

doi = {10.1016/j.ajcnut.2025.04.019},

issn = {0002-9165},

year  = {2025},

date = {2025-04-01},

journal = {American Journal of Clinical Nutrition},

abstract = {BACKGROUND: The primary protein source of a diet may impact skeletal muscle maintenance with advancing age. The impact of the animal and plant protein content of a typical protein-containing diet on muscle anabolism in middle-to-older aged adults is unknown. OBJECTIVES: To determine muscle adaptive remodelling response to a 10-day dietary intervention containing divergent protein sources, with and without resistance exercise training (RET) in middle-to-older aged adults. METHODS: In a single-blind randomized control trial, twenty-seven 50-70-year-old participants consumed 1.0g$cdot$kg BM $cdot$day of protein from an animal-focused whey protein-supplemented diet (AW-D) or plant-focused pea protein-supplemented diet (PP-D). Throughout the 10-day diet intervention, unilateral knee extensor RET was performed every other day. Deuterated water ingestion and skeletal muscle biopsies enabled measurement of daily integrated myofibrillar protein synthesis (iMyoPS) rates in the trained, and untrained legs. Changes in metabolic rate, body composition, lipid profiles, renal function, whole-body nitrogen balance (WBNB), strength and muscle architecture were also determined. RESULTS: Daily iMyoPS rates were significantly greater (P$<$0.001) in the trained compared to the untrained leg for AW-D (1.44 ± 0.26 vs 1.29 ± 0.27 %$cdot$day ) and PP-D (1.50 ± 0.17 vs 1.34 ± 0.21 %$cdot$day ) with no differences between groups, within leg. Training and diet did not affect intracellular anabolic signalling, muscle architecture, strength, metabolic rate, renal function or WBNB. Serum non-HDL cholesterol was significantly (P=0.014) lower following the intervention for PP-D only (pre: 3.89 ± 0.84, post 3.37 ± 0.78 mmol$cdot$L) with no other changes in lipid profiles. CONCLUSIONS: The 10-day provision of 1.0g$cdot$kg BM $cdot$day from predominantly plant-derived or animal-derived protein does not influence daily iMyoPS rates in middle-to-older aged adults and has little impact on metabolic and renal health parameters. RET enhances rates of daily iMyoPS in middle-to-older aged adults consuming a typical protein-containing diet, with no influence of protein source. CLINICAL TRIAL REGISTRY NUMBER: ClinicalTrials.gov NCT05574205 https://clinicaltrials.gov/study/NCT05574205.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{betz2025a,

title = {Aerobic Exercise Preconditioning Does Not Augment Muscle Hypertrophy During Subsequent Resistance Exercise Training in Healthy Older Adults},

author = {Milan W Betz and Alejandra P Monsegue and Lisanne H P Houben and Floris K Hendriks and Janneau Kranenburg and Thorben Aussieker and Bouke P Adriaans and Alfons J H M Houben and Lex B Verdijk and Luc J C Loon and Tim Snijders},

doi = {10.1007/s40279-025-02229-y},

issn = {0112-1642},

year  = {2025},

date = {2025-04-01},

journal = {Sports Medicine},

volume = {55},

pages = {2323–2338},

abstract = {BACKGROUND: Resistance exercise training is an effective treatment strategy to counteract the age-related loss of muscle mass and strength in older adults. However, there is a large inter-individual variation in muscle fiber hypertrophy following resistance exercise training. It has been hypothesized that a less than optimal muscle fiber capillarization and perfusion capacity may compromise muscle hypertrophy during resistance exercise training in older adults. OBJECTIVE: We assessed whether 8~weeks of aerobic exercise preconditioning, to improve muscle fiber capillarization and perfusion capacity, augments the gains in muscle mass and strength during subsequent resistance exercise training in older adults. METHODS: In total, 34 healthy older males and females (71~years standard deviation (SD) ± 5~years) participated in 12~weeks of progressive resistance exercise training, preceded by either 8~weeks of aerobic preconditioning (AER},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{betz2025,

title = {Post-Exercise Cooling Lowers Skeletal Muscle Microvascular Perfusion and Blunts Amino Acid Incorporation into Muscle Tissue in Active Young Adults},

author = {Milan W Betz and Cas J Fuchs and Finlay Chedd and Alejandra P Monsegue and Floris K Hendriks and Janneau M X Kranenburg and Joy Goessens and Alfons J H M Houben and Lex B Verdijk and Luc J C Loon and Tim Snijders},

doi = {10.1249/MSS.0000000000003723},

issn = {0195-9131},

year  = {2025},

date = {2025-04-01},

journal = {Medicine and Science in Sports and Exercise},

abstract = {PURPOSE: Cold-water immersion lowers muscle protein synthesis rates during post-exercise recovery. Whether this effect can be explained by lower muscle microvascular perfusion and a subsequent decline in post-prandial amino acid incorporation into muscle tissue following cooling is currently unknown. METHODS: Twelve young males (24 ± 4 y) performed a single resistance exercise session followed by water immersion for 20 min with one leg immersed in cold water (8 $^circ$C: COLD) and the contralateral leg in thermoneutral water (30 $^circ$C: CON). After immersion, a beverage was ingested containing 20 g free amino acids, 0.25 g L-[ring-13C6]-phenylalanine, and 45 g carbohydrates. Microvascular perfusion of the vastus lateralis muscle was assessed for both legs using contrast-enhanced ultrasound at rest, immediately following exercise and water immersion, and at t = 60 and t = 180 min following beverage ingestion. A muscle biopsy sample (vastus lateralis) was collected from both legs (t = 240 min) to determine amino acid tracer incorporation. RESULTS: Microvascular blood volume was significantly lower in the COLD vs CON leg immediately following water immersion (1.24 ± 0.82 vs 3.13 ± 1.64 video intensity, respectively, P $<$ 0.001) and remained lower at t = 60 and t = 180 min following beverage ingestion (0.90 ± 0.84 vs 1.53 ± 0.98, and 2.10 ± 2.53 vs 2.77 ± 2.81 video intensity, respectively, both P $<$ 0.05). Exogenous amino acid incorporation into muscle protein was lower in the COLD vs CON leg (0.011 ± 0.004 vs 0.016 ± 0.005 mole percent excess, respectively, P $<$ 0.001). The difference in post-prandial amino acid incorporation into muscle protein between the COLD and CON leg was strongly associated with the difference in microvascular blood volume between the two legs during recovery (r = 0.65, P $<$ 0.05). CONCLUSIONS: Cold-water immersion during post-exercise recovery greatly reduces muscle microvascular perfusion and blunts post-prandial amino acid incorporation in muscle.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{hilkens2025,

title = {Bone Health of Female Elite Cyclists Is Characterized by Impaired Cortical and Trabecular Microarchitecture},

author = {Luuk Hilkens and Melissa S A M Bevers and Caroline E Wyers and Luc J C Loon and Joop P Bergh and Jan-Willem Dijk},

doi = {10.1249/MSS.0000000000003718},

issn = {0195-9131},

year  = {2025},

date = {2025-04-01},

journal = {Medicine and Science in Sports and Exercise},

abstract = {PURPOSE: Many elite road-race cyclists have low areal bone mineral density (aBMD) as previously shown by dual-energy X-ray absorptiometry (DXA). However, aBMD provides limited insight into bone quality. Therefore, this cross-sectional study aimed to assess volumetric BMD (vBMD), bone microarchitecture, and bone strength in elite road-race cyclists using high-resolution peripheral computed tomography (HR-pQCT), along with aBMD measured by DXA. METHODS: Twenty female elite (Tier 3/ 4) road-race cyclists (21 ± 2 y; BMI 20.8 ± 1.6 kg/m2) had DXA scans at the hip, lumbar spine, and total body to assess aBMD, and HR-pQCT scans at the distal radius and tibia to assess vBMD, bone microarchitecture, and failure load. Z-scores were calculated for all outcomes, with Z-scores $<$-1 considered as low or impaired. The risk of low energy availability was assessed using the Low Energy Availability in Females Questionnaire (LEAF-Q). RESULTS: Low aBMD was observed in 20%, 25%, 35%, and 10% of the participants at the hip, femoral neck, lumbar spine, and total body, respectively. Low total vBMD was present in 45% and 40% at the distal radius and tibia, respectively. With regard to bone microarchitecture, the tibial cortical area and tibial cortical thickness were low in 40% and 60% of the participants, respectively, and number and thickness of trabeculae at the tibia were low in 40% and 30% of the participants. The impairments were less pronounced at the distal radius. Failure load was low in 15% (radius) and 20% (tibia) of the participants. CONCLUSIONS: Along with low aBMD, a substantial proportion of female elite cyclists had impaired bone microarchitecture, mainly characterized by a low cortical area and thickness and low trabecular number and thickness, especially at the distal tibia.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{aussieker2025,

title = {Ingestion of a Whey Plus Collagen Protein Blend Increases Myofibrillar and Muscle Connective Protein Synthesis Rates},

author = {Thorben Aussieker and Jeremias Kaiser and Wesley J H Hermans and Floris K Hendriks and Andrew M Holwerda and Joan M Senden and Janneau M X Kranenburg and Joy P B Goessens and Ulrike Braun and Keith Baar and Tim Snijders and Luc J C Loon},

doi = {10.1249/MSS.0000000000003596},

issn = {0195-9131},

year  = {2025},

date = {2025-03-01},

journal = {Medicine and Science in Sports and Exercise},

volume = {57},

number = {3},

pages = {544–554},

abstract = {Purpose: Ingestion of whey protein increases myofibrillar but not muscle connective protein synthesis rates. Recently, we defined a whey and collagen protein blend (5:1-ratio) to optimize post-prandial plasma amino acid availability. Here, we assessed the ability of this blend to increase myofibrillar and muscle connective protein synthesis rates at rest and during early recovery from exercise. Methods: In a randomized, double-blind, parallel design, 28 men (age: 25±5 y; BMI: 23.6±2.3 kg/m 2) were randomly allocated to ingest either 30 g of protein (25 g whey/5 g collagen; BLEND},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pinckaers2025,

title = {Oleuropein Supplementation Increases Resting Skeletal Muscle Fractional PDH Activity but Does Not Influence Whole-Body Metabolism: A Randomized, Double-Blind, Placebo-Controlled Trial in Healthy, Older Males},

author = {Philippe Jm Pinckaers and Heather L Petrick and Astrid Mh Horstman and Alba Moreno-Asso and Umberto De Marchi and Floris K Hendriks and Lisa Me Kuin and Cas J Fuchs and Dominik Grathwohl and Lex B Verdijk and Antoine H Zorenc and Joan Mg Senden and Eugenia Migliavacca and Sylviane Metairon and Laure Poquet and Delphine Morin-Rivron and Leonidas G Karagounis and Graham P Holloway and Jerome N Feige and Luc Jc Loon},

doi = {10.1016/j.tjnut.2025.02.015},

issn = {0022-3166},

year  = {2025},

date = {2025-02-01},

journal = {Journal of Nutrition},

abstract = {BACKGROUND: The polyphenol oleuropein activates mitochondrial calcium import, which increases pyruvate dehydrogenase (PDH) activity. Preclinically, this increase in PDH activity following oleuropein supplementation resulted in improved mitochondrial bioenergetics and fatigue resistance. OBJECTIVE: This study aimed to examine the effects of acute and chronic oleuropein supplementation on muscle energy metabolism, whole-body substrate metabolism, strength, and fatigue resistance in older males. METHODS: In a randomized, double-blind, placebo-controlled trial, 40 healthy older males (60±5y) received either placebo (PLA) or 100mg oleuropein from olive leaf extract (OLE) supplementation daily for 36 days. On day 1 and 36, muscle and blood samples were collected, and indirect calorimetry was performed, before and up to 120min following supplement intake. Leg strength and fatigue were measured before and after 29 days of supplementation. Results were analyzed using ANCOVA or robust ANCOVA. RESULTS: OLE ingestion on day 1 and 36 increased plasma oleuropein metabolites (P$<$0.001). On day 1, no differences were observed in muscle PDH activity, mitochondrial respiration, or whole-body substrate metabolism 120min after acute OLE ingestion. RNA sequencing revealed upregulation of oxidative phosphorylation gene pathways (FDR$<$0.05), while PDH-Ser -phosphorylation was higher after acute OLE vs PLA ingestion (P=0.015). Following chronic supplementation, fractional PDH activity was textasciitilde25% greater in OLE vs PLA (49±14 vs 38±10%; P=0.016) with no differences in absolute PDH activity and PDH-Ser -phosphorylation between groups. Mitochondrial respiration and protein content, whole-body substrate metabolism, leg strength and fatigue resistance, were not different between OLE vs PLA. Plasma LDL cholesterol was lower after chronic OLE vs PLA (P=0.043) with no differences in other blood metabolic markers. CONCLUSIONS: Chronic OLE supplementation resulted in higher skeletal muscle fractional PDH activity in healthy, older males, which may impact resting energy metabolism. Acute or chronic oleuropein supplementation do not modulate skeletal muscle mitochondrial respiration, muscle strength, muscle fatigue, or whole-body substrate metabolism. CLINICAL TRIAL REGISTRATION: Https://clinicaltrials.gov/study/NCT05217433. Registry: https://clinicaltrials.gov/study/NCT05217433.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{lim2025,

title = {Turning over New Ideas in Human Skeletal Muscle Proteostasis: What Do We Know and Where to from Here?},

author = {Changhyun Lim and James Mckendry and Matthew Lees and Philip J. Atherton and Nicholas A. Burd and Andrew M. Holwerda and Luc J. C. Loon and Chris Mcglory and Cameron J. Mitchell and Kenneth Smith and Daniel J. Wilkinson and Tanner Stokes and Stuart M. Phillips},

doi = {10.1113/EP092353},

issn = {0958-0670},

year  = {2025},

date = {2025-02-01},

journal = {Experimental Physiology},

number = {EP092353},

abstract = {Understanding the turnover of proteins in tissues gives information as to how external stimuli result in phenotypic change. Nowhere is such phenotypic change more conspicuous than skeletal muscle, which can be effectively remodelled by increased loading, ageing and unloading (disuse), all of which are subject to modification by nutrition and other environmental stimuli. The understanding of muscle proteome remodelling has undergone a renaissance recently with the reintroduction of deuterated water (D2O) and its ingestion to label amino acids and measure their incorporation into proteins. However, there is confusion around the use of the deuterated water methodology and the interpretation of the data it provides. Here, we provide a short review of some of the more salient features of the method and clarify some of the confusion around the method of deuterated water methods and its use in humans and how the interpretation of the data is in contrast to that of rodents.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{weijer2025,

title = {Measured and Predicted Resting Metabolic Rate of Dutch and Norwegian Paralympic Athletes},

author = {Vera C R Weijer and Kristin L Jonvik and Lotte Dam and Linn Risvang and Truls Raastad and Luc J C Loon and Jan-Willem Dijk},

doi = {10.1016/j.jand.2024.05.010},

issn = {2212-2672},

year  = {2025},

date = {2025-02-01},

journal = {Journal of the Academy of Nutrition and Dietetics},

volume = {125},

number = {2},

pages = {217-227.e5},

abstract = {Background: Although resting metabolic rate (RMR) is crucial for understanding athletes' energy requirements, limited information is available on the RMR of Paralympic athletes. Objective: The aim of this study was to determine RMR and its predictors in a diverse cohort of Paralympic athletes and evaluate the agreement between measured and predicted RMR from both newly developed and pre-existing equations. Design: This cross-sectional study, conducted between September 2020 and September 2022 in the Netherlands and Norway, assessed RMR in Paralympic athletes by means of ventilated hood indirect calorimetry and body composition by means of dual-energy x-ray absorptiometry. Participants: Sixty-seven Paralympic athletes (male: n = 37; female: n = 30) competing in various sports, with a spinal cord disorder (n = 22), neurologic condition (n = 8), limb deficiency (n = 18), visual or hearing impairment (n = 7), or other disability (n = 12) participated. Main outcome measures: RMR, fat-free mass (FFM), body mass, and triiodothyronine (T3) concentrations were assessed. Statistical analyses: Multiple regression analyses were conducted with height, FFM, body mass, sex, T3 concentration, and disabilities as potential predictors of RMR. Differences between measured and predicted RMRs were analyzed for individual accuracy, root mean square error, and intraclass correlation. Results: Mean ± SD RMR was 1386 ± 258 kcal/d for females and 1686 ± 302 kcal/d for males. Regression analysis identified FFM, T3 concentrations, and the presence of a spinal cord disorder, as the main predictors of RMR (adjusted R 2 = 0.71; F = 50.3; P $<$ .001). The novel prediction equations based on these data, as well as pre-existing equations of Chun and colleagues and Nightingale and Gorgey performed well on accuracy ($>$60% of participants within 10% of measured RMR), had good reliability (intraclass correlation $>$0.78), and low root mean square error ($łeq$141 kcal). Conclusions: FFM, total T3 concentrations, and presence of spinal cord disorder are the main predictors of RMR in Paralympic athletes. Both the current study's prediction equations and those from Chun and colleagues and Nightingale and Gorgey align well with measured RMR, offering accurate prediction equations for the RMR of Paralympic athletes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{korzepa2025,

title = {Postprandial Plasma Amino Acid and Appetite Responses to a Low Protein Breakfast Supplemented with Whey or Pea Protein in Middle-to-Older Aged Adults},

author = {Marie Korzepa and Ryan N Marshall and Lucy M Rogers and Archie E Belfield and Jonathan I Quinlan and Yijia Huang and Ari Gritsas and Tyler A Churchward-Venne and Elisa I Glover and Luc J C Loon and Gareth A Wallis and Leigh Breen},

doi = {10.1007/s00394-025-03605-0},

issn = {1436-6207},

year  = {2025},

date = {2025-02-01},

journal = {European Journal of Nutrition},

volume = {64},

number = {2},

abstract = {The addition of low-dose protein to low protein-containing meals in middle-to-older aged adults may promote greater postprandial plasma aminoacidemia and mitigate declines in muscle health but may be dependent on the source and quality of protein consumed. This single-blind randomised study investigated postprandial plasma aminoacidemia and appetite regulatory responses to a typical lower protein-containing (textasciitilde0.07~g$cdot$kg body mass[BM] ) mixed breakfast supplemented with textasciitilde0.13~g$cdot$kg BM of whey protein concentrate (MB + WPC) or pea protein isolate (MB + PPI) in middle-to-older aged adults. Venous blood samples were collected whilst fasted and over a 180-min postprandial period to determine plasma amino acid and appetite hormone concentrations. Perceived appetite ratings were measured using Visual Analogue Scales. Plasma total amino acids and essential amino acids increased over time (both P $<$ 0.05) with no between-group differences or overall availability over 180~min (incremental area under the curve (iAUC)). Plasma leucine concentrations increased over time (both P $<$ 0.05) with greater peak concentrations (P = 0.032) and iAUC (P = 0.012) in MB + WPC compared with MB + PPI. Plasma total-ghrelin and total-GLP-1 concentrations and perceived ratings of hunger, fullness, and satiety were transiently altered following MB + WPC and MB + PPI (P $<$ 0.05 for all), with no differences between groups. In middle-to-older aged adults, co-ingesting a small bolus of whey protein alongside a typical lower protein-containing breakfast elicits greater plasma leucinemia than co-ingestion of pea protein, with no differential impact on appetite regulation. Whether the addition of low-dose whey protein to typical meals of middle-to-older aged adults can enhance muscle anabolism without adversely affecting appetite remains to be determined.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{malowany2025,

title = {The Indicator Amino Acid Oxidation (IAAO) Technique: A Novel Approach to Assess Protein Intakes That Maximize Whole-Body Protein Anabolism},

author = {Julia M. Malowany and Glenn A. A. Lieshout and Lex B. Verdijk and Daniel R. Moore and Luc J. C. Loon and Jorn Trommelen},

url = {https://www.scopus.com/pages/publications/105012256706},

doi = {10.1080/10408398.2025.2541895},

issn = {1040-8398},

year  = {2025},

date = {2025-01-01},

urldate = {2025-09-12},

journal = {Critical Reviews in Food Science and Nutrition},

abstract = {Dietary protein requirement is defined as the daily intake at which whole-body protein net balance remains in equilibrium and body protein is maintained. Protein intakes to meet the dietary requirement (the Recommended Daily Allowance, RDA; 0.83 g proteinkg BM-1d-1) were determined using nitrogen balance methodology. More recently, studies using indirect Indicator Amino Acid Oxidation (IAAO) breakpoint analysis suggest a RDA value of 1.20 g proteinkg BM-1d-1. However, since breakpoint analysis determines the protein intake at which whole-body protein net balance is maximized, we suggest the value determined by IAAO analysis represents the maximal anabolic protein intake, not a protein requirement. Several aspects of the IAAO method should be considered prior to its application and/or interpretation, such as: (1) extrapolation of hourly to daily values; (2) extrapolation of free amino acid sip-feeding to whole-foods, and; (3) misidentification of the upper limit of the 95% confidence interval as the intake level that covers 98% of the population. We conclude that the current IAAO method represents a minimally invasive technique allowing elegant within-subject designs to assess the maximal anabolic protein intake. Therefore, data derived from such studies should not be misinterpreted as an estimate of protein requirements.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{aussieker2025b,

title = {The Effects of Ingesting a Single Bolus of Hydrolyzed Collagen versus Free Amino Acids on Muscle Connective Protein Synthesis Rates},

author = {Thorben Aussieker and Jeremias Kaiser and Floris K. Hendriks and Tom A. H. Janssen and Joan M. Senden and Janneau M. X. Van Kranenburg and Joy P. B. Goessens and Antoine Zorenc and Esther Kornips and Tjinta Brinkhuizen and Keith Baar and Tim Snijders and Andrew M. Holwerda and Luc J. C. Van Loon},

doi = {10.1249/MSS.0000000000003788},

issn = {0195-9131},

year  = {2025},

date = {2025-01-01},

urldate = {2025-01-01},

journal = {Medicine and Science in Sports and Exercise},

number = {3788},

abstract = {The suggested anabolic properties of hydrolyzed collagen on connective tissue may be attributed to the delivery of amino acids as precursors or to anabolic signaling properties of bioactive peptides.

Purpose 

To assess the impact of ingesting a single bolus of hydrolyzed collagen or free amino acids on myofibrillar and muscle connective protein synthesis rates.

Methods 

In a randomized, double-blind, parallel design, 45 young male (n = 21) and female (n = 24) adults (age: 23 ± 3 y; BMI: 22.3 ± 2.2 kg/m2) received intravenous infusions with L-[ring-13C6]-phenylalanine. Following unilateral resistance exercise, participants ingested either 30 g hydrolyzed collagen (COLL, n = 15), 30 g free amino acids reflecting the collagen amino acid profile (AA, n = 15), or a non-caloric placebo (PLA, n = 15). Blood and muscle tissue samples were collected over 6 h to assess myofibrillar and muscle connective protein synthesis rates and associated signaling responses.

Results 

Both collagen and free amino acid ingestion substantially increased circulating plasma amino acids concentrations and effected collagen turnover proteins. Collagen and free amino acid ingestion did not significantly increase myofibrillar protein synthesis rates in the rested (0.039 ± 0.011, 0.037 ± 0.010, and 0.036 ± 0.015%·h−1 in PLA, COLL and AA, respectively) or the exercised (0.049 ± 0.010, 0.048 ± 0.011, and 0.045 ± 0.013%·h−1) leg (P > 0.05). Similarly, both collagen and free amino acid ingestion did not significantly increase muscle connective protein synthesis rates in the rested (0.065 ± 0.014, 0.063 ± 0.017, and 0.061 ± 0.025%·h−1 in PLA, COLL and AA, respectively) or the exercised (0.098 ± 0.023, 0.092 ± 0.028, and 0.085 ± 0.024%·h−1) leg (P > 0.05).

Conclusions 

Ingestion of a single bolus of collagen hydrolysate or free amino acids substantially increases circulating amino acids concentrations, particularly glycine, but does not further increase myofibrillar or muscle connective protein synthesis rates at rest or during recovery from exercise in healthy, recreationally active young men and women.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{fuchs2025a,

title = {Quantifying Leg Muscle Disuse Atrophy During Bed Rest Using DXA, CT, and MRI},

author = {Cas J. Fuchs and Wesley J. H. Hermans and Job Hurk and Christopher J. Wiggins and Per Widholm and Olof Dahlqvist Leinhard and Pandichelvam Veeraiah and Joachim E. Wildberger and Jeanine J. Prompers and Luc J. C. Loon},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ejsc.12299},

doi = {10.1002/ejsc.12299},

issn = {1536-7290},

year  = {2025},

date = {2025-01-01},

urldate = {2025-05-03},

journal = {European Journal of Sport Science},

volume = {25},

number = {5},

pages = {e12299},

abstract = {This study evaluated whether dual-energy X-ray absorptiometry (DXA), computed tomography (CT), and magnetic resonance imaging (MRI) provide comparable outcomes in quantifying disuse-induced skeletal muscle atrophy. Although the calculation of muscle volume using MRI analysis may be considered the gold standard, the method remains labor intense and, as such, less practical and more costly. In this context, we also evaluated the efficacy of a commercially available automated MRI analysis method to measure changes in leg muscle volume after two weeks of bed rest. Twelve healthy, male adults (age: 24 ± 3 years, BMI: 23.7 ± 3.1 kg/m2) were subjected to 2 weeks of strict bed rest. Leg muscle assessments were performed before and after bed rest using DXA, single slice (thigh) CT, and MRI. MRI data analyses were performed using both a manual and automated (AMRA) method. Leg lean mass, as assessed with DXA, declined by 5% following bed rest (from 10.2 ± 1.6 to 9.7 ± 1.6 kg; p $<$ 0.001). The thigh muscle cross-sectional area, as assessed with CT, declined by 6% following bed rest (from 155 ± 26 to 146 ± 24 cm2; p $<$ 0.001). Muscle volume, as assessed using MRI, declined by 5% following bed rest, both when assessed manually (from 7.1 ± 1.1 to 6.7 ± 1.0 L; p $<$ 0.001) and automatically (from 7.2 ± 1.1 to 6.8 ± 1.0 L; p $<$ 0.001). A very strong correlation (r = 0.96; p $<$ 0.001) with a low bias (-0.11 ± 0.29 L) was observed between manual and automated muscle volume analysis. DXA, CT, and MRI all show a $sim$5% decline in leg muscle quantity following two weeks of bed rest in healthy adults. When using MRI, disuse muscle atrophy can be accurately quantified using an automated approach, rendering time-consuming manual analysis obsolete.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{vanlieshout2025,

title = {Protein Glycation Compromises the Bioavailability of Milk Protein-Derived Lysine in Vivo in Healthy Adult Males: A Double-Blind Randomized Cross-over Trial},

author = {Glenn Aa Lieshout and Jorn Trommelen and Jean Nyakayiru and Janneau Kranenburg and Joan M Senden and Annemie P Gijsen and Lex B Verdijk and Wilbert F Pellikaan and Marjolijn Ce Bragt and Luc Jc Loon},

doi = {10.1016/j.ajcnut.2025.01.025},

issn = {0002-9165},

year  = {2025},

date = {2025-01-01},

journal = {American Journal of Clinical Nutrition},

abstract = {BACKGROUND: Industrial processing and storage of milk products can strongly increase protein glycation level. Previously, we have reported that ingestion of highly glycated milk protein attenuates the post-prandial rise in plasma lysine concentrations when compared to the ingestion of an equivalent amount of milk protein with a low glycation level. Whether the attenuated increase in plasma lysine availability is attributed to compromised protein digestion and subsequent lysine absorption remains to be established. OBJECTIVE: The present study combined stable isotope methodology with the ingestion of, specifically produced, intrinsically labeled protein to assess protein digestion and amino acid absorption following ingestion of milk protein with a high versus low glycation level in vivo in humans. METHODS: 15 recreationally active, healthy young males participated in this double-blinded, randomized cross-over study. Subjects ingested 40 g intrinsically L-[1- C]-lysine-labeled milk protein with either a low (3%) or high (50%) glycation level. Continuous intravenous infusion of L-[4,4,5,5- H ]-lysine was combined with frequent blood sample collection during a 6-h post-prandial period to evaluate dietary protein-derived lysine release into the circulation. RESULTS: Post-prandial plasma lysine concentrations were lower following the ingestion of milk protein with a high versus low glycation level (time*treatment effect: P=0.002; ? =0.214), resulting in a 23 mmol$cdot$L $cdot$360 min [95%-CI:13-32] lower incremental area under the curve (0±12 vs 23±11 mmol$cdot$L $cdot$360 min , respectively, P$<$0.001). The post-prandial release of milk protein-derived lysine into the circulation was attenuated following ingestion of the protein with the high versus low glycation level (time*treatment effect: P$<$0.001; ? =0.640) and was 31% [95%-CI:26-36] lower over the full 6-h post-prandial period (18±4 vs 49±10% of the ingested lysine, respectively, P$<$0.001). CONCLUSIONS: A high level of milk protein glycation strongly reduces post-prandial plasma lysine availability in vivo in humans. Industrial processing and storage of (milk) protein products can strongly modulate protein bioavailability and, as such, lower the nutritional value of a protein source. This trial was registered at www. CLINICALTRIALS: gov as NCT05479916: https://clinicaltrials.gov/study/NCT05479916.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{fuchs2025,

title = {Repeated Passive Heat Treatment Increases Muscle Tissue Capillarization, but Does Not Affect Postprandial Muscle Protein Synthesis Rates in Healthy Older Adults},

author = {Cas J. Fuchs and Milan W. Betz and Heather L. Petrick and Jil Weber and Joan M. Senden and Floris K. Hendriks and Julia L. M. Bels and Luc J. C. Loon and Tim Snijders},

doi = {10.1113/JP286986},

issn = {0022-3751},

year  = {2025},

date = {2025-01-01},

journal = {Journal of Physiology},

volume = {603},

number = {1},

pages = {167–186},

abstract = {Abstract: Prolonged passive heat treatment (PHT) has been suggested to trigger skeletal muscle adaptations that may improve muscle maintenance in older individuals. To assess the effects of PHT on skeletal muscle tissue capillarization, perfusion capacity, protein synthesis rates, hypertrophy and leg strength, 14 older adults (9~males, 5 females; 73 ± 6~years) underwent 8~weeks of PHT (infrared sauna: 3× per week, 45~min at $sim$60$^circ$C). Before and after PHT we collected muscle biopsies to assess skeletal muscle capillarization and fibre cross-sectional area (CSA). Basal and postprandial muscle tissue perfusion kinetics and protein synthesis rates were assessed using contrast-enhanced ultrasound and primed continuous l-[ring- 13C 6]phenylalanine infusions, respectively. One-repetition maximum (1RM) leg strength and vastus lateralis muscle CSA were assessed. Type I and type II muscle fibre capillarization strongly increased following PHT (capillary-to-fibre perimeter exchange index: +31 ± 18 and +33 ± 30%, respectively; P~$<~$0.001). No changes were observed in basal (0.24 ± 0.27 vs. 0.18 ± 0.11 AU; P~=~0.266) or postprandial (0.20 ± 0.12 vs. 0.18 ± 0.14 AU; P~=~0.717) microvascular blood flow following PHT. Basal (0.048 ± 0.014 vs. 0.051 ± 0.019%/h; P~=~0.630) and postprandial (0.041 ± 0.012 vs. 0.051 ± 0.024%/h; P~=~0.199) muscle protein synthesis rates did not change in response to prolonged PHT. Furthermore, no changes in vastus lateralis muscle CSA (15.3 ± 4.6 vs. 15.2 ± 4.6 cm 2; P~=~0.768) or 1RM leg strength (46 ± 12 vs. 47 ± 12 kg; P~=~0.087) were observed over time. In conclusion, prolonged PHT increases muscle tissue capillarization but this does not improve muscle microvascular blood flow or increase muscle protein synthesis rates in healthy, older adults. Prolonged PHT does not induce skeletal muscle hypertrophy or increase leg strength in healthy, older adults. (Figure presented.). Key points: Repeated exposure to heat has been suggested to trigger skeletal muscle adaptive responses. We investigated the effect of 8~weeks of whole-body passive heat treatment (PHT; infrared sauna: 3× per week for 45~min at $sim$60$^circ$C) on skeletal muscle tissue capillarization, perfusion capacity, basal, and postprandial muscle protein synthesis rates, muscle (fibre) hypertrophy, and leg strength in healthy, older adults. Prolonged PHT increases muscle tissue capillarization, but this does not improve muscle microvascular blood flow or increase muscle protein synthesis rates. Despite increases in muscle tissue capillarization, prolonged PHT does not suffice to induce skeletal muscle hypertrophy or increase leg strength in healthy, older adults.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{weijer2024,

title = {Continuous Glucose Monitoring in Para Cyclists: An Observational Study},

author = {Vera Weijer and Rob Werf and Myrthe Haijden and Asker Jeukendrup and Luc J. C. Loon and Jan-Willem Dijk},

doi = {10.1002/ejsc.12220},

issn = {1746-1391},

year  = {2024},

date = {2024-12-01},

journal = {European Journal of Sport Science},

volume = {24},

number = {12},

pages = {1809–1819},

abstract = {Continuous glucose monitoring (CGM) is an emerging tool for dietary counseling in athletes. This study aimed to explore blood glucose profiles in Para cyclists and evaluate CGM accuracy at rest and during exercise. Thirteen Para cyclists, comprising eight hand bikers and five cyclists, wore a CGM sensor (Abbott) for 2 weeks. Participants recorded the timing of meals and regular training sessions and executed one standardized training session. Fifteen capillary blood glucose reference values (seven at rest and eight during the standardized training) were obtained by finger pricks. Mean glucose concentrations and time spent in hypoglycemia ($<$3.9 mmol/L), euglycemia (3.9-7.8 mmol/L), and hyperglycemia ($>$7.8 mmol/L) were calculated over 24 hrs and during daytime, nighttime, exercise, and 2 hrs postprandial periods. Mean absolute relative differences (MARD) were calculated between the CGM and capillary blood glucose. The mean glucose concentration over the 24 hr-period was 5.7 (5.6-5.8) mmol/L. Athletes were in the euglycemia range 91% of the time. Hyperglycemia was almost exclusively observed postprandially and during exercise. Hypoglycemia was restricted to the night and was particularly observed in athletes with a spinal cord injury. CGM accuracy was acceptable at rest (MARD: 12%) but markedly lower during exercise (MARD: 34%; p = 0.01), especially for hand bikers (MARD: 41%) compared with cyclists (MARD: 24%; p = 0.01). Para cyclists generally do not display signs of disturbed glucose regulation. However, the increased risk for nocturnal hypoglycemia in athletes with a spinal cord injury warrants attention. Furthermore, CGM accuracy is compromised during exercise, especially if the sensor is in proximity to highly active muscles.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{mezincescu2024,

title = {Comparison of Intramyocellular Lipid Metabolism in Patients with Diabetes and Male Athletes},

author = {Alice M. Mezincescu and Amelia Rudd and Lesley Cheyne and Graham Horgan and Sam Philip and Donnie Cameron and Luc Loon and Phil Whitfield and Rachael Gribbin and May Khei Hu and Mirela Delibegovic and Barbara Fielding and Gerald Lobley and Frank Thies and David E. Newby and Stuart Gray and Anke Henning and Dana Dawson},

doi = {10.1038/s41467-024-47843-y},

issn = {2041-1723},

year  = {2024},

date = {2024-12-01},

journal = {Nature Communications},

volume = {15},

number = {1},

abstract = {Despite opposing insulin sensitivity and cardiometabolic risk, both athletes and patients with type 2 diabetes have increased skeletal myocyte fat storage: the so-called ``athlete's paradox''. In a parallel non-randomised, non-blinded trial (NCT03065140), we characterised and compared the skeletal myocyte lipid signature of 29 male endurance athletes and 30 patients with diabetes after undergoing deconditioning or endurance training respectively. The primary outcomes were to assess intramyocellular lipid storage of the vastus lateralis in both cohorts and the secondary outcomes were to examine saturated and unsaturated intramyocellular lipid pool turnover. We show that athletes have higher intramyocellular fat saturation with very high palmitate kinetics, which is attenuated by deconditioning. In contrast, type 2 diabetes patients have higher unsaturated intramyocellular fat and blunted palmitate and linoleate kinetics but after endurance training, all were realigned with those of deconditioned athletes. Improved basal insulin sensitivity was further associated with better serum cholesterol/triglycerides, glycaemic control, physical performance, enhanced post insulin receptor pathway signalling and metabolic sensing. We conclude that insulin-resistant, maladapted intramyocellular lipid storage and turnover in patients with type 2 diabetes show reversibility after endurance training through increased contributions of the saturated intramyocellular fatty acid pools. Clinical Trial Registration: NCT03065140: Muscle Fat Compartments and Turnover as Determinant of Insulin Sensitivity (MISTY).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{houtvast2024,

title = {Underpowered Studies in Muscle Metabolism Research: Determinants and Considerations},

author = {Dion C J Houtvast and Milan W Betz and Bas Van Hooren and Sophie Vanbelle and Lex B Verdijk and Luc J C Loon and Jorn Trommelen},

doi = {10.1016/j.clnesp.2024.10.152},

issn = {2405-4577},

year  = {2024},

date = {2024-12-01},

journal = {Clinical Nutrition ESPEN},

volume = {64},

pages = {334–343},

abstract = {Biomedical research frequently employs null hypothesis testing to determine whether an observed difference in a sample is likely to exist in the broader population. Null hypothesis testing generally assumes that differences between groups or interventions are non-existent, unless proven otherwise. Because biomedical studies with human subjects are often limited by financial and logistical resources, they tend to have low statistical power, i.e. a low probability of statistically confirming a true difference. As a result, small but potentially clinically important differences may be overseen or ignored simply due to the absence of a statistically significant difference. This absence is often misinterpreted as 'equivalence' of treatments. In this educational paper, we will use practical examples related to the effects of exercise and nutrition on muscle protein metabolism to illustrate the most important determinants of statistical power, as well as their implications for both investigators and readers of scientific articles. Changes in muscle mass occur at a relatively slow rate, making it practically challenging to detect differences between treatment groups in a long-term setting. One way to make it 'easier' to differentiate between groups and hence increase statistical power is to have a sufficiently long study duration to allow treatment effects to become apparent. This is especially relevant when comparing treatments with relatively small expected differences such as the effect of modest changes in daily protein intake. Secondly, one could try to minimize the variance and response heterogeneity within groups, for example by using strict inclusion criteria and standardization protocols (e.g., meal provision), by using cross-over designs, or even within-subject designs where two interventions are compared simultaneously (e.g., studying an exercised limb vs a contralateral control limb) although this might limit the generalizability of the findings (e.g. such single-limb exercise training is not common in practice). In terms of data interpretation, investigators should obviously refrain from drawing strong conclusions from underpowered studies. Yet, such studies still provide valuable data for meta-analyses. Finally, because muscle protein synthesis rates are highly responsive to anabolic stimuli, acute metabolic studies are more sensitive to detect potentially clinically relevant differences in the anabolic response between treatments. Apart from further elaborating on these topics, this educational article encourages readers to more critically question null findings and scientists to more clearly discuss limitations that may have compromised statistical power.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{kouw2024,

title = {Short-Term Intermittent Fasting and Energy Restriction Do Not Impair Rates of Muscle Protein Synthesis: A Randomised, Controlled Dietary Intervention},

author = {Imre W. K. Kouw and Evelyn B. Parr and Michael J. Wheeler and Bridget E. Radford and Rebecca C. Hall and Joan M. Senden and Joy P. B. Goessens and Luc J. C. Loon and John A. Hawley},

doi = {10.1016/j.clnu.2024.09.034},

issn = {0261-5614},

year  = {2024},

date = {2024-11-01},

journal = {Clinical Nutrition},

volume = {43},

number = {11},

pages = {174–184},

abstract = {Background: Intermittent fasting (IF) is an effective energy restricted dietary strategy to reduce body and fat mass and improve metabolic health in individuals with either an overweight or obese status. However, dietary energy restriction may impair muscle protein synthesis (MPS) resulting in a concomitant decline in lean body mass. Due to periods of prolonged fasting combined with irregular meal intake, we hypothesised that IF would reduce rates of MPS compared to an energy balanced diet with regular meal patterns. Aims: We assessed the impact of a short-term, ten days, alternate day fasting or a continuous energy restricted diet to a control diet on integrated rates of skeletal MPS in middle-aged males with overweight or obesity. Methods: Twenty-seven middle-aged males with overweight or obesity (age: 44.6 ± 5.4 y; BMI: 30.3 ± 2.6 kg/m2) consumed a three-day lead-in diet, followed by a ten-day controlled dietary intervention matched for protein intake, as alternate day fasting (ADF: 62.5 energy (En)%, days of 25 En% alternated with days of 100 En% food ingestion), continuous energy restriction (CER: 62.5 En%), or an energy balanced, control diet (CON: 100 En%). Deuterated water (D2O) methodology with saliva, blood, and skeletal muscle sampling were used to assess integrated rates of MPS over the ten-day intervention period. Secondary measures included fasting plasma glucose, insulin, and gastrointestinal hormone concentrations, continuous glucose monitoring, and assessment of body composition. Results: There were no differences in daily rates of MPS between groups (ADF: 1.18 ± 0.13, CER: 1.13 ± 0.16, and CON: 1.18 ± 0.18 %/day, P $>$ 0.05). The reductions in body mass were greater in ADF and CER compared to CON (P $<$ 0.001). Lean and fat mass were decreased by a similar magnitude across groups (main time effect, P $<$ 0.001; main group effect, P $>$ 0.05). Fasting plasma leptin concentrations decreased in ADF and CER (P $<$ 0.001), with no differences in fasting plasma glucose or insulin concentrations between groups. Conclusion: Short-term alternate day fasting does not lower rates of MPS compared to continuous energy restriction or an energy balanced, control diet with matched protein intake. The prolonged effects of IF and periods of irregular energy and protein intake patterns on muscle mass maintenance remain to be investigated. This trial was registered under Australian New Zealand Clinical Trial Registry (https://www.anzctr.org.au), identifier no. ACTRN12619000757112.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{holwerda2024b,

title = {Assessing Muscle Protein Synthesis Rates in Vivo in Humans: The Deuterated Water (2H2O) Method},

author = {Andrew M Holwerda and Philip J Atherton and Kenneth Smith and Daniel J Wilkinson and Stuart M Phillips and Luc J C Loon},

doi = {10.1016/j.tjnut.2024.09.012},

issn = {0022-3166},

year  = {2024},

date = {2024-11-01},

journal = {Journal of Nutrition},

volume = {154},

number = {11},

pages = {3177–3189},

abstract = {Skeletal muscle tissue is in a constant state of turnover, with muscle tissue protein synthesis and breakdown rates ranging between 1% and 2% across the day in vivo in humans. Muscle tissue remodeling is largely controlled by the up- and down-regulation of muscle tissue protein synthesis rates. Research studies generally apply stable isotope-labeled amino acids to assess muscle protein synthesis rates in vivo in humans. Following labeled amino acid administration in a laboratory setting, muscle tissue samples are collected over several hours to assess the incorporation rate of these labeled amino acids in muscle tissue protein. To allow quantification of bulk muscle protein synthesis rates over more prolonged periods, the use of deuterated water methodology has regained much interest. Ingestion of daily boluses of deuterium oxide results in 2H enrichment of the body water pool. The available 2H-atoms become incorporated into endogenously synthesized alanine primarily through transamination of pyruvate in the liver. With 2H-alanine widely available to all tissues, it becomes incorporated into de novo synthesized tissue proteins. Assessing the increase in tissue protein-bound 2H-alanine enrichment in muscle biopsy samples over time allows for the calculation of muscle protein synthesis rates over several days or even weeks. As the deuterated water method allows for the assessment of muscle tissue protein synthesis rates under free-living conditions in nonlaboratory settings, there is an increasing interest in its application. This manuscript describes the theoretical background of the deuterated water method and offers a comprehensive tutorial to correctly apply the method to determine bulk muscle protein synthesis rates in vivo in humans.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{betz2024a,

title = {Muscle Fibre Satellite Cells Are Located at a Greater Distance from Capillaries in Patients with COPD Compared with Healthy Controls},

author = {Milan W Betz and Jana De Brandt and Thorben Aussieker and Alejandra P Monsegue and Dion C J Houtvast and Sebastian Gehlert and Lex B Verdijk and Luc J C Loon and Harry R Gosker and Ramon J C Langen and Wim Derave and Chris Burtin and Martijn A Spruit and Tim Snijders},

doi = {10.1183/23120541.00203-2024},

issn = {2312-0541},

year  = {2024},

date = {2024-09-01},

journal = {ERJ Open Research},

volume = {10},

number = {5},

abstract = {Background COPD is a disease characterised by skeletal muscle dysfunction. A spatial relationship exists between satellite cells and muscle fibre capillaries, which has been suggested to be of major importance for satellite cell function. In the present study we compared the spatial relationship between satellite cells and capillaries in patients with COPD and age-matched healthy older adults. Methods Muscle biopsies were obtained from the vastus lateralis of n=18 patients with COPD (8 female, 10 male; age 66±5 years, mild-to-severe airflow obstruction) and n=18 age-, sex-and body mass index-matched healthy control adults (8 female, 10 male; age 68±5 years). Immunohistochemistry was used to assess type I/II muscle fibre size, distribution, myonuclear content, satellite cell number and fibre capillarisation. In addition, type I/II muscle fibre satellite cell distance to its nearest capillary was assessed. Results The percentage of type II muscle fibres was significantly greater in patients with COPD (62±10%) compared with controls (50±12%, p$<$0.05). Muscle fibre capillarisation was significantly lower in patients with COPD compared with controls (p$<$0.05). While satellite cell content was not different between groups, type I and type II satellite cell distance to its nearest capillary was significantly greater in patients with COPD (type I: 21.3±4.8 µm; type II: 26.7±9.3 µm) compared with controls (type I: 16.1±3.5 µm; type II: 22.7±5.8 µm; p$<$0.05). Conclusion Satellite cells are located at a greater distance from their nearest capillary in patients with COPD compared with age-matched controls. This increased distance could play a role in impaired satellite cell function in patients with COPD.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{weijzen2024,

title = {Reply - Letter to the Editor: Access to a Pre-Sleep Protein Snack Increases Daily Energy and Protein Intake in Surgical Hospitalized Patients},

author = {Michelle E. G. Weijzen and Luc J. C. Loon},

doi = {10.1016/j.clnu.2024.06.032},

issn = {0261-5614},

year  = {2024},

date = {2024-08-01},

journal = {Clinical Nutrition},

volume = {43},

number = {8},

pages = {1888–1889},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{schenaarts2024,

title = {A Single Sauna Session Does Not Improve Postprandial Blood Glucose Handling in Individuals with Type 2 Diabetes Mellitus: A Cross-over, Randomized, Controlled Trial},

author = {Laura Schenaarts and Floris K Hendriks and Cas J Fuchs and Wendy Em Sluijsmans and Tim Snijders and Luc Jc Loon},

doi = {10.1055/a-2406-4491},

issn = {1439-3646},

year  = {2024},

date = {2024-08-01},

journal = {Experimental and clinical endocrinology & diabetes},

abstract = {INTRODUCTION: Passive heat treatment has been suggested to improve glycaemic control in individuals with type 2 diabetes mellitus. Previous studies have predominantly focused on hot water immersion and traditional sauna bathing, as opposed to the more novel method of infrared-based sauna bathing. Here we assessed the impact of a single infrared sauna session on post-prandial glycaemic control in older individuals with type 2 diabetes mellitus. METHODS: In this randomized controlled crossover trial, 12 participants with type 2 diabetes mellitus (male/female: 10/2, age: 69±7 y, BMI: 27.5±2.9 kg/m ) rested in an infrared sauna twice: once in a heated condition (60$^circ$C) and once in a thermoneutral condition (21$^circ$C) for 40 min, immediately followed by a 2-h oral glucose tolerance test (OGTT). Venous blood samples were obtained to assess plasma glucose and insulin concentrations and to determine the whole-body composite insulin sensitivity index. RESULTS: Body core and leg skin temperature were higher following the heated condition compared to the thermoneutral condition (38.0±0.3 vs 36.6±0.2$^circ$C and 39.4±0.8 vs 31.3±0.8$^circ$C, respectively; $<$0.001 for both). The incremental area under the curve (iAUC) of plasma glucose concentrations during the OGTT was higher after the heated condition compared to the thermoneutral condition (17.7±3.1 vs 14.8±2.8 mmol/L/120 min; $<$0.001). No differences were observed in plasma insulin concentrations (heated: 380±194 vs thermoneutral: 376±210 pmol/L/120 min; =0.93) or whole-body composite insulin sensitivity indexes (4.5±2.8 vs 4.5±2.1; =0.67). A single infrared sauna session does not improve postprandial blood glucose handling in individuals with type 2 diabetes mellitus. Future studies should assess the effect of more prolonged application of infrared sauna bathing on daily glycaemic control.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{hengist2024,

title = {Ketogenic Diet but Not Free-Sugar Restriction Alters Glucose Tolerance, Lipid Metabolism, Peripheral Tissue Phenotype, and Gut Microbiome: RCT},

author = {Aaron Hengist and Russell G Davies and Jean-Philippe Walhin and Jariya Buniam and Lucy H Merrell and Lucy Rogers and Louise Bradshaw and Alfonso Moreno-Cabañas and Peter J Rogers and Jeff M Brunstrom and Leanne Hodson and Luc J C Loon and Wiley Barton and Ciara O'Donovan and Fiona Crispie and Orla O'Sullivan and Paul D Cotter and Kathryn Proctor and James A Betts and Françoise Koumanov and Dylan Thompson and Javier T Gonzalez},

doi = {10.1016/j.xcrm.2024.101667},

issn = {2666-3791},

year  = {2024},

date = {2024-08-01},

journal = {Cell Reports Medicine},

number = {101667},

abstract = {Restricted sugar and ketogenic diets can alter energy balance/metabolism, but decreased energy intake may be compensated by reduced expenditure. In healthy adults, randomization to restricting free sugars or overall carbohydrates (ketogenic diet) for 12~weeks reduces fat mass without changing energy expenditure versus control. Free-sugar restriction minimally affects metabolism or gut microbiome but decreases low-density lipoprotein cholesterol (LDL-C). In contrast, a ketogenic diet decreases glucose tolerance, increases skeletal muscle PDK4, and reduces AMPK and GLUT4 levels. By week 4, the ketogenic diet reduces fasting glucose and increases apolipoprotein B, C-reactive protein, and postprandial glycerol concentrations. However, despite sustained ketosis, these effects are no longer apparent by week 12, when gut microbial beta diversity is altered, possibly reflective of longer-term adjustments to the ketogenic diet and/or energy balance. These data demonstrate that restricting free sugars or overall carbohydrates reduces energy intake without altering physical activity, but with divergent effects on glucose tolerance, lipoprotein profiles, and gut microbiome.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{trommelen2024a,

title = {Protein Intake Distribution: Beneficial, Detrimental, or Inconsequential for Muscle Anabolism? Response to Witard & Mettler},

author = {Jorn Trommelen and Andrew M Holwerda and Luc J C Loon},

doi = {10.1123/ijsnem.2024-0107},

issn = {1526-484X},

year  = {2024},

date = {2024-07-01},

journal = {International Journal of Sport Nutrition and Exercise Metabolism},

pages = {1–4},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{holwerda2024,

title = {Mitochondrial Bioenergetics Are Not Associated with Myofibrillar Protein Synthesis Rates},

author = {Andrew M. Holwerda and Marlou L. Dirks and Pierre-Andre Barbeau and Joy Goessens and Annemie Gijsen and Luc J. C. Loon and Graham P. Holloway},

doi = {10.1002/jcsm.13532},

issn = {2190-5991},

year  = {2024},

date = {2024-07-01},

journal = {Journal of cachexia, sarcopenia and muscle},

abstract = {Background Mitochondria represent key organelles influencing cellular homeostasis and have been implicated in the signalling events regulating protein synthesis. Methods We examined whether mitochondrial bioenergetics (oxidative phosphorylation and reactive oxygen species (H2O2) emission, ROS) measured in vitro in permeabilized muscle fibres represent regulatory factors for integrated daily muscle protein synthesis rates and skeletal muscle mass changes across the spectrum of physical activity, including free-living and bed-rest conditions: n = 19 healthy, young men (26 +/- 4 years, 23.4 +/- 3.3 kg/m(2)) and following 12 weeks of resistance-type exercise training: n = 10 healthy older men (70 +/- 3 years, 25.2 +/- 2.1 kg/m(2)). Additionally, we evaluated the direct relationship between attenuated mitochondrial ROS emission and integrated daily myofibrillar and sarcoplasmic protein synthesis rates in genetically modified mice (mitochondrial-targeted catalase, MCAT). Results Neither oxidative phosphorylation nor H2O2 emission were associated with muscle protein synthesis rates in healthy young men under free-living conditions or following 1 week of bed rest (both P $>$ 0.05). Greater increases in GSSG concentration were associated with greater skeletal muscle mass loss following bed rest (r = -0.49, P $<$ 0.05). In older men, only submaximal mitochondrial oxidative phosphorylation (corrected for mitochondrial content) was positively associated with myofibrillar protein synthesis rates during exercise training (r = 0.72, P $<$ 0.05). However, changes in oxidative phosphorylation and H2O2 emission were not associated with changes in skeletal muscle mass following training (both P $>$ 0.05). Additionally, MCAT mice displayed no differences in myofibrillar (2.62 +/- 0.22 vs. 2.75 +/- 0.15%/day) and sarcoplasmic (3.68 +/- 0.35 vs. 3.54 +/- 0.35%/day) protein synthesis rates when compared with wild-type mice (both P $>$ 0.05). Conclusions Mitochondrial oxidative phosphorylation and reactive oxygen emission do not seem to represent key factors regulating muscle protein synthesis or muscle mass regulation across the spectrum of physical activity.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{hilkens2024a,

title = {A Single Bout of Jumping Exercise Does Not Modulate Serum Markers of Bone Formation or Bone Resorption throughout a 24 h Period},

author = {Luuk Hilkens and Judith Bons and Jean Nyakayiru and Luc J C Loon and Jan-Willem Dijk},

doi = {10.1016/j.bone.2024.117216},

issn = {8756-3282},

year  = {2024},

date = {2024-07-01},

journal = {Bone},

number = {117216},

abstract = {INTRODUCTION: This randomized, cross-over trial assessed the effect of a single bout of high-impact exercise on serum markers of bone formation and bone resorption over a 24~h period. METHODS: Twenty healthy males and females performed a single bout of brief jumping exercise (EXC) or no exercise (CON), 55~min following consumption of a standard breakfast. Blood markers of bone formation (P1NP) and bone resorption (CTXI) were assessed before (t~=~0~h) and over a 5~h period after breakfast, and following 24~h of post-exercise recovery (t~=~24~h). RESULTS: Serum CTX-I concentrations decreased during the 5~h postprandial period (time-effect, P~$<~$0.001) with no differences between conditions (time x condition, P~=~0.14). After a~textasciitilde~16~% decline during the first 30~min following breakfast, serum P1NP concentrations gradually returned to baseline values during the 5~h postprandial period, with no differences in the overall response between conditions (time-effect, P~$<~$0.001; time x condition, P~=~0.25). Fasted serum CTX-I concentrations decreased from 0.33~±~0.15 and 0.35~±~0.15~ng/mL at baseline, to 0.31~±~0.13 and 0.31~±~0.16~ng/mL at t~=~24~h in CON and EXC, respectively, with no differences between conditions (time-effect, P~$<~$0.01; time x condition, P~=~0.70). Fasted serum P1NP concentrations did not change from baseline to t~=~24~h in both CON (baseline: 76~±~27~ng/mL, t~=~24~h: 79~±~26~ng/mL) and EXC (baseline: 80~±~24~ng/mL, t~=~24~h: 77~±~29~ng/mL; time-effect, P~=~0.89), with no differences between conditions (time x condition, P~=~0.22). CONCLUSION: High-impact exercise does not modulate the concentrations of the serum marker of bone formation P1NP and the serum marker of bone resorption CTX-I throughout a 24~h recovery period in healthy adults.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{aussieker2024,

title = {Coingestion of Collagen With Whey Protein Prevents Postexercise Decline in Plasma Glycine Availability in Recreationally Active Men},

author = {Thorben Aussieker and Tom A H Janssen and Wesley J H Hermans and Andrew M Holwerda and Joan M Senden and Janneau M X Kranenburg and Joy P B Goessens and Tim Snijders and Luc J C Loon},

doi = {10.1123/ijsnem.2023-0264},

issn = {1526-484X},

year  = {2024},

date = {2024-07-01},

journal = {International Journal of Sport Nutrition and Exercise Metabolism},

volume = {34},

number = {4},

pages = {189–198},

abstract = {Whey protein ingestion during recovery from exercise increases myofibrillar but not muscle connective protein synthesis rates. It has been speculated that whey protein does not provide sufficient glycine to maximize postexercise muscle connective protein synthesis rates. In the present study, we assessed the impact of coingesting different amounts of collagen with whey protein as a nutritional strategy to increase plasma glycine availability during recovery from exercise. In a randomized, double-blind, crossover design, 14 recreationally active men (age: 26 ± 5 years; body mass index: 23.8 ± 2.1 kg m-2) ingested in total 30 g protein, provided as whey protein with 0 g (WHEY), 5 g (WC05); 10 g (WC10), and 15 g (WC15) of collagen protein immediately after a single bout of resistance exercise. Blood samples were collected frequently over 6 hr of postexercise recovery to assess postprandial plasma amino acid kinetics and availability. Protein ingestion strongly increased plasma amino acid concentrations (p $<$ .001) with no differences in plasma total amino acid availability between treatments (p $>$ .05). The postprandial rise in plasma leucine and essential amino acid availability was greater in WHEY compared with the WC10 and WC15 treatments (p $<$ .05). Plasma glycine and nonessential amino acid concentrations declined following whey protein ingestion but increased following collagen coingestion (p $<$ .05). Postprandial plasma glycine availability averaged -8.9 ± 5.8, 9.2 ± 3.7, 23.1 ± 6.5, and 39.8 ± 11.0 mmol 360 min/L in WHEY, WC05, WC10, and WC15, respectively (incremental area under curve values, p $<$ .05). Coingestion of a small amount of collagen (5 g) with whey protein (25 g) is sufficient to prevent the decline in plasma glycine availability during recovery from lower body resistancetype exercise in recreationally active men.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{weijer2024a,

title = {Do Paralympic Athletes Suffer from Brittle Bones? Prevalence and Risk Factors of Low Bone Mineral Density in Paralympic Athletes},

author = {Vera C. R. Weijer and Jan Willem Dijk and Lotte Dam and Linn Risvang and Judith Bons and Truls Raastad and Luc J. C. Loon and Kristin L. Jonvik},

doi = {10.1016/j.bonr.2024.101767},

issn = {2352-1872},

year  = {2024},

date = {2024-06-01},

journal = {Bone Reports},

volume = {21},

number = {101767},

abstract = {Background: Bone health may be a concern in Paralympic athletes, given the presence of multiple risk factors predisposing these athletes to low bone mineral density (BMD). Objective: We aimed to assess the prevalence of low BMD among Paralympic athletes participating in various sport disciplines, and to identify potential risk factors for low BMD. Methods: Seventy Paralympic athletes, of whom 51 % were wheelchair-dependent, were included in this cross-sectional study. BMD of the whole-body, lumbar spine, total hip, and femoral neck were assessed by dual-energy x-ray absorptiometry. Comparisons between groups were conducted by one-way ANOVA, and regression analyses were conducted to identify potential risk factors for low BMD. Results: The prevalence of low BMD (Z-score $<$ -1.0) was highest at femoral neck (34 %), followed by total hip (31 %), whole-body (21 %), and lumbar spine (18 %). Wheelchair-dependent athletes had significantly lower BMD Z-scores compared to the non-wheelchair-dependent athletes at whole-body level (-0.5 ± 1.4 vs 0.2 ± 1.3; P = 0.04), total hip (-1.1 ± 1.2 vs 0.0 ± 1.1; P $<$ 0.01), and femoral neck (-1.0 ± 1.3 vs -0.1 ± 1.2; P $<$ 0.01). At the lumbar spine, low BMD was completely absent in wheelchair basketball and tennis players. Regression analyses identified body mass, wheelchair dependence, and type of sport, as the main risk factors for low BMD. Conclusions: In this cohort of Paralympic athletes, low BMD is mainly present at the hip, and to a lesser extent at the whole-body and lumbar spine. The most prominent risk factors for low BMD in Paralympic athletes are related to mechanical loading patterns, including wheelchair use, the type of sport, and body mass.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{weijzen2024a,

title = {Access to a Pre-Sleep Protein Snack Increases Daily Energy and Protein Intake in Surgical Hospitalized Patients},

author = {Michelle E. G. Weijzen and Maxime Kohlen and Alejandra Monsegue and Dion C. J. Houtvast and Jean Nyakayiru and Sandra Beijer and Phil Geerlings and Lex B. Verdijk and Luc J. C. Loon},

doi = {10.1016/j.clnu.2024.03.016},

issn = {0261-5614},

year  = {2024},

date = {2024-05-01},

journal = {Clinical Nutrition},

volume = {43},

number = {5},

pages = {1073–1078},

abstract = {Background & aim: In hospitalized patients, daily protein intake remains far below WHO requirements for healthy adults (0.8 g$cdot$kg-1$cdot$d-1) as well as ESPEN guidelines for patients (1.2–1.5 g$cdot$kg-1$cdot$d-1). Providing access to a pre-sleep protein dense snack between dinner and going to bed may serve as a great opportunity to increase daily energy and protein intake in hospitalized patients. However, it remains to be assessed whether protein provision prior to sleep effectively increases protein intake, or may reduce food intake throughout the remainder of the day(s). The present study evaluated the impact of giving access to a pre-sleep snack on daily energy and protein intake in patients throughout their hospitalization. Methods: Patients admitted to the surgical wards of the Maastricht University Medical Centre+ were randomly allocated to usual care (n = 51) or given access to a pre-sleep snack (n = 50). The pre-sleep snack consisted of 103 g cheese cubes (30 g protein) provided between 7:30 and 9:30 PM, prior to sleep. All food provided and all food consumed was weighed and recorded throughout (2–7 days) hospitalization. Daily energy and protein intake and distribution were calculated. Data were analyzed by independent T-Tests with P $<$ 0.05 considered as statistically significant. Results: Daily energy intake was higher in the pre-sleep group (1353 ± 424 kcal d-1) when compared to the usual care group (1190 ± 402 kcal$cdot$d-1; P = 0.049). Providing patients access to a pre-sleep snack resulted in a 17% (11 ± 9 g) higher daily protein intake (0.81 ± 0.29 g$cdot$kg-1$cdot$d-1) when compared to the usual care group (0.69 ± 0.28 g$cdot$kg-1$cdot$d-1; P = 0.045). Protein intake at breakfast, lunch, and dinner did not differ between the pre-sleep and usual care groups (all P $>$ 0.05). Conclusion: Providing access to a pre-sleep protein snack, in the form of protein dense food items such as cheese, represents an effective dietary strategy to increase daily energy and protein intake in hospitalized patients. Patients consuming pre-sleep protein snacks do not compensate by lowering energy or protein intake throughout the remainder of the days. Pre-sleep protein dense food provision should be implemented in hospital food logistics to improve the nutritional intake of patients. Trial register no: NL8507 (https://trialsearch.who.int/)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{trommelen2024,

title = {Quantification and Interpretation of Postprandial Whole-Body Protein Metabolism Using Stable Isotope Methodology: A Narrative Review},

author = {Jorn Trommelen and Luc J. C. Loon},

doi = {10.3389/fnut.2024.1391750},

issn = {2296-861X},

year  = {2024},

date = {2024-05-01},

journal = {Frontiers in nutrition},

volume = {11},

number = {1391750},

abstract = {Stable isotopes are routinely applied to determine the impact of factors such as aging, disease, exercise, and feeding on whole-body protein metabolism. The most common approaches to quantify whole-body protein synthesis, breakdown, and oxidation rates and net protein balance are based on the quantification of plasma amino acid kinetics. In the postabsorptive state, plasma amino acid kinetics can easily be assessed using a constant infusion of one or more stable isotope labeled amino acid tracers. In the postprandial state, there is an exogenous, dietary protein-derived amino acid flux that needs to be accounted for. To accurately quantify both endogenous as well as exogenous (protein-derived) amino acid release in the circulation, the continuous tracer infusion method should be accompanied by the ingestion of intrinsically labeled protein. However, the production of labeled protein is too expensive and labor intensive for use in more routine research studies. Alternative approaches have either assumed that 100% of exogenous amino acids are released in the circulation or applied an estimated percentage based on protein digestibility. However, such estimations can introduce large artifacts in the assessment of whole-body protein metabolism. The preferred estimation approach is based on the extrapolation of intrinsically labeled protein-derived plasma bioavailability data obtained in a similar experimental design setting. Here, we provide reference data on exogenous plasma amino acid release that can be applied to allow a more accurate routine assessment of postprandial protein metabolism. More work in this area is needed to provide a more extensive reference data set.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{monsegue2024,

title = {Resistance Exercise Training to Improve Post-Operative Rehabilitation in Knee Arthroplasty Patients: A Narrative Review},

author = {Alejandra P. Monsegue and Pieter Emans and Luc J. C. Loon and Lex B. Verdijk},

doi = {10.1002/ejsc.12114},

issn = {1746-1391},

year  = {2024},

date = {2024-05-01},

journal = {European Journal of Sport Science},

abstract = {Knee osteoarthritis is associated with deficits in muscle strength, muscle mass, and physical functioning. These muscle-related deficits are acutely exacerbated following total knee arthroplasty (TKA) and persist long after surgery, despite the application of standardized rehabilitation programs that include physical/functional training. Resistance exercise training (RET) has been shown to be a highly effective strategy to improve muscle-related outcomes in healthy as well as clinical populations. However, the use of RET in traditional rehabilitation programs after TKA is limited. In this narrative review, we provide an updated view on whether adding RET to the standard rehabilitation (SR) in the recovery period (up to 1 year) after TKA leads to greater improvements in muscle-related outcomes when compared to SR alone. Overall, research findings clearly indicate that both muscle strength and muscle mass can be improved to a greater extent with RET-based rehabilitation compared to SR. Additionally, measures of physical functioning that rely on quadriceps strength and balance (e.g., stair climbing, chair standing, etc.) also appear to benefit more from a RET-based program compared to SR, especially in patients with low levels of physical functioning. Importantly though, for RET to be optimally effective, it should be performed at 70%-80% of the one-repetition maximum, with 3-4 sets per exercise, with a minimum of 3 times per week for 8 weeks. Based upon this narrative review, we recommend that such high-intensity progressive RET should be incorporated into standard programs during rehabilitation after TKA.Schematic summary of this narrative review. Osteoarthritis is associated with a decline in muscle strength, mass, and function (1). After total knee replacement a further decline in muscle strength, mass, and function is observed (2). Although standard rehabilitation results in a partial or (sometimes) full recovery in these outcomes (3a), rehabilitation involving high-intensity resistance exercise training leads to greater improvements in muscle strength, muscle mass, and physical functioning compared to standard rehabilitation (3b). imageFollowing standard rehabilitation (SR) protocols, patients recovering from total knee replacement still have deficits in muscle strength, muscle mass, and physical functioning compared to their healthy counterparts. Rehabilitation involving high-intensity resistance exercise training (RET) following total knee replacement leads to greater improvements in muscle strength, muscle mass, and physical functioning compared to SR. We recommend incorporating high intensity RET in the SR following total knee arthroplasty.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{hendriks2024,

title = {Hemodialysis Does Not Lower Circulating Testosterone Concentrations},

author = {Floris K Hendriks and Jos Wiersma and Frank M Sande and Sarah E Alexander and Jeroen P Kooman and Judith A P Bons and Luc J C Loon},

doi = {10.1007/s40620-023-01810-w},

issn = {1121-8428},

year  = {2024},

date = {2024-05-01},

journal = {Journal of Nephrology},

volume = {37},

number = {4},

pages = {1125–1127},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{bland2024,

title = {``It Gave Me a Sense of Achievement and a Sense of Purpose''—a Qualitative Study of Patient Experiences of a Virtually Supervised Exercise Program for Adults with Advanced Cancer and Cachexia},

author = {Kelcey A. Bland and Madeleine France-Ratcliffe and Meinir Krishnasamy and Amruta Nandi and Evelyn B. Parr and Peter Martin and Prue Cormie and Luc J. C. Loon and Eva M. Zopf},

doi = {10.1007/s00520-024-08526-y},

issn = {0941-4355},

year  = {2024},

date = {2024-05-01},

journal = {Supportive Care in Cancer},

volume = {32},

number = {5},

abstract = {Abstract: People with advanced cancer and cachexia experience significant body weight loss, adversely impacting physical function and quality of life (QOL). Effective, evidence-based treatments for cancer cachexia are lacking, leaving patients with unmet needs. Exercise holds promise to improve patient QOL. However, information on patients' experiences of exercise, including their ability to cope with structured exercise, is limited. Purpose: To explore patient experiences completing a structured, supervised exercise program for people with cachexia due to advanced cancer. Methods: Semi-structured interviews were conducted with participants enrolled in a phase II feasibility, randomized controlled trial to explore their experiences of an 8-week virtually supervised exercise program delivered via videoconference technology. Interviews were analysed using reflexive thematic analysis. Results: Seventeen participants completed interviews (female n = 9, 53%). Main interview themes included the following: (1) Deciding to exercise involves balancing concerns and expectations, (2) the exercise program is a positive experience, and (3) moving forward after the exercise program. While some participants initially held doubts about their physical capabilities and exercise safety, most wanted to exercise to enhance their wellbeing. Participants described the exercise program as a positive experience, offering diverse benefits. Some would have preferred in-person exercise, but all agreed the virtual format increased convenience. Participants emphasized the need to recommend the program to others in similar circumstances. They underscored the necessity and desire for ongoing support to sustain their new exercise habits. Conclusion: Based on patient experiences, virtually supervised exercise programming appears to be feasible and meaningful to people with advanced cancer and cachexia.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pinckaers2024a,

title = {Post-Prandial Muscle Protein Synthesis Rates Following the Ingestion of Pea-Derived Protein Do Not Differ from Ingesting an Equivalent Amount of Milk-Derived Protein in Healthy, Young Males},

author = {Philippe J M Pinckaers and Joey S J Smeets and Imre W K Kouw and Joy P B Goessens and Annemarie P B Gijsen and Lisette C P G M Groot and Lex B Verdijk and Luc J C Loon and Tim Snijders},

doi = {10.1007/s00394-023-03295-6},

issn = {1436-6215},

year  = {2024},

date = {2024-04-01},

journal = {European journal of nutrition},

volume = {63},

number = {3},

pages = {893–904},

abstract = {PURPOSE: Plant-derived proteins have received considerable attention as an alternative to animal-derived proteins. However, plant-derived proteins are considered to have less anabolic properties when compared with animal-derived proteins. The lower muscle protein synthesis rates following ingestion of plant- compared with animal-derived protein have been attributed to the lower essential amino acid content of plant-derived proteins and/or their specific amino acid deficiencies. This study aimed to compare post-prandial muscle protein synthesis rates following the ingestion of 30 g pea-derived protein with 30 g milk-derived protein in healthy, young males.nnMETHODS: In a randomized, double-blind, parallel-group design, 24 young males (24 ± 3 y) received a primed continuous L-[ring-C]-phenylalanine infusion after which they ingested 30 g pea (PEA) or 30 g milk-derived protein (MILK). Blood and muscle biopsies were collected frequently for 5 h to assess post-prandial plasma amino acid profiles and subsequent post-prandial muscle protein synthesis rates.nnRESULTS: MILK increased plasma essential amino acid concentrations more than PEA over the 5 h post-prandial period (incremental area under curve 151 ± 31 vs 102 ± 15 mmol$bullet$300 min$bullet$L, respectively; P ¡ 0.001). Ingestion of both MILK and PEA showed a robust muscle protein synthetic response with no significant differences between treatments (0.053 ± 0.013 and 0.053 ± 0.017%$bullet$h, respectively; P = 0.96).nnCONCLUSION: Post-prandial muscle protein synthesis rates following the ingestion of 30 g pea-derived protein do not differ from the response following ingestion of an equivalent amount of milk-derived protein. International Clinical Trials Registry Platform (NTR6548; 27-06-2017).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{houben2024a,

title = {A Low or High Physical Activity Level Does Not Modulate Prostate Tumor Tissue Protein Synthesis Rates},

author = {Lisanne H P Houben and Tom Tuytten and Andrew M Holwerda and Erika Wisanto and Joan Senden and Will K W H Wodzig and Steven W M Olde Damink and Milou Beelen and Sandra Beijer and Koenraad VAN Renterghem and Luc J C VAN Loon},

doi = {10.1249/MSS.0000000000003349},

issn = {1530-0315},

year  = {2024},

date = {2024-04-01},

journal = {Medicine and science in sports and exercise},

volume = {56},

number = {4},

pages = {635–643},

abstract = {INTRODUCTION: Physical activity level has been identified as an important factor in the development and progression of various types of cancer. In this study, we determined the impact of a low versus high physical activity level on skeletal muscle, healthy prostate, and prostate tumor protein synthesis rates in vivo in prostate cancer patients.nnMETHODS: Thirty prostate cancer patients (age, 66 ± 5 yr; body mass index, 27.4 ± 2.9 kg$cdot$m -2 ) were randomized to a low (¡4000 steps per day},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{holwerda2024a,

title = {One Week of Single-Leg Immobilization Lowers Muscle Connective Protein Synthesis Rates in Healthy, Young Adults},

author = {Andrew M Holwerda and Michelle E G Weijzen and Antoine Zorenc and Joan Senden and Guus H J Jetten and Lisanne H P Houben and Lex B Verdijk and Luc J C VAN Loon},

doi = {10.1249/MSS.0000000000003342},

issn = {1530-0315},

year  = {2024},

date = {2024-04-01},

urldate = {2024-04-01},

journal = {Medicine and science in sports and exercise},

volume = {56},

number = {4},

pages = {612–622},

abstract = {PURPOSE: Short periods of limb immobilization lower myofibrillar protein synthesis rates. Within skeletal muscle, the extracellular matrix of connective proteins is recognized as an important factor determining the capacity to transmit contractile force. Little is known regarding the impact of immobilization and subsequent recovery on muscle connective protein synthesis rates. This study examined the impact of 1 wk of leg immobilization and 2 wk of subsequent ambulant recovery on daily muscle connective protein synthesis rates. METHODS: Thirty healthy, young (24 ± 5 yr) men were subjected to 7 d of one-legged knee immobilization followed by 14 d of ambulant recovery. Deuterium oxide ingestion was applied over the entire period, and muscle biopsy samples were collected before immobilization, after immobilization, and after recovery to measure muscle connective protein synthesis rates and mRNA expression of key extracellular matrix proteins (collagen I, collagen III), glycoproteins (fibronectin, tenascin-C), and proteoglycans (fibromodulin, and decorin). A two-way repeated-measures (time-leg) ANOVA was used to compare changes in muscle connective protein synthesis rates during immobilization and recovery. RESULTS: During immobilization, muscle connective protein synthesis rates were lower in the immobilized (1.07 ± 0.30%$cdot$d -1 ) compared with the nonimmobilized (1.48 ± 0.44%$cdot$d -1 ; P < 0.01) leg. When compared with the immobilization period, connective protein synthesis rates in the immobilized leg increased during subsequent recovery (1.48 ± 0.64%$cdot$d -1 ; P < 0.01). After recovery, skeletal muscle collagen I, collagen III, fibronectin, fibromodulin, and decorin mRNA expression increased when compared with the postimmobilization time point (all P < 0.001). CONCLUSIONS: One week of leg immobilization lowers muscle connective protein synthesis rates. Muscle connective protein synthesis rates increase during subsequent ambulant recovery, which is accompanied by increased mRNA expression of key extracellular matrix proteins.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{domic2024,

title = {A Well-Balanced Vegan Diet Does Not Compromise Daily Mixed Muscle Protein Synthesis Rates When Compared with an Omnivorous Diet in Active Older Adults: A Randomized Controlled Cross-Over Trial},

author = {Jacintha Domic and Philippe Jm Pinckaers and Pol Grootswagers and Els Siebelink and Johanna C Gerdessen and Luc Jc Loon and Lisette Cpgm Groot},

doi = {10.1016/j.tjnut.2024.12.019},

issn = {0022-3166},

year  = {2024},

date = {2024-04-01},

urldate = {2025-04-01},

journal = {Journal of Nutrition},

volume = {155},

issue = {4},

pages = {1141-1150},

abstract = {Background: Plant-based foods have reduced protein digestibility and frequently display unbalanced amino acid profiles. Plant-based foods are therefore considered inferior to animal-based foods in their anabolic potential. No study has assessed the anabolic potential of a vegan diet that provides a large variety of plant-based protein sources in older adults. Objectives: To investigate the effect of a 10-d vegan diet on daily mixed muscle protein synthesis (MPS) rates in comparison with an isocaloric, isonitrogenous, omnivorous diet in community-dwelling older adults. Methods: This cross-over trial assessed 34 community-dwelling older adults (72 ± 4 y, 18 males, 16 females), who were randomly assigned to consume a 10-d controlled vegan diet, followed by a controlled omnivorous diet (60% animal protein), or vice versa. One day before the study diets, participants consumed 400 mL deuterated water, followed by daily doses of 50 mL. Subsequent plasma and muscle samples were collected during the intervention period. Physical activity levels were assessed using accelerometry. Secondary outcomes were cardiometabolic risk factors and appetite. Statistical analyses were performed using linear mixed models, and results are presented as means ± standard errors. Results: Integrated MPS rates did not differ between the vegan (1.23 ± 0.04%/d) and omnivorous (1.29 ± 0.04%/d) diets (P = 0.2542). Plasma low-density lipoprotein (Δ0.23 ± 0.03, P $<$ 0.0001), high-density lipoprotein (Δ0.03 ± 0.14},

keywords = {},

pubstate = {published},

tppubtype = {article}

}