Resistance-type Exercise Training Research Articles

Collagen Peptide Supplementation during Training Does Not Further Increase Connective Tissue Protein Synthesis Rates.

Protein supplementation increases post-exercise muscle protein synthesis rates and, as such, supports exercise-induced muscle conditioning. Collagen protein has been suggested as the preferred protein source to stimulate muscle connective protein synthesis rates during recovery from exercise. Here we assessed the effects of hydrolyzed collagen peptide supplementation on both myofibrillar as well as muscle connective protein synthesis rates during one week of strenuous resistance exercise training. In a randomized, double-blind, parallel design, 25 young men (24 ± 3 y, 76.9 ± 6.4 kg) were selected to perform one week of intense resistance-type exercise training. Subjects were randomly assigned into two groups receiving either 15 g hydrolyzed collagen peptides (COL) or a non-caloric placebo (PLA) twice daily during the intervention. Subjects were administered deuterated water (2H2O) daily, with blood and skeletal muscle tissue samples being collected prior to and after the intervention to determine daily myofibrillar and muscle connective protein synthesis rates. Post-absorptive plasma glycine, proline, and hydroxyproline concentrations increased following collagen peptide supplementation (p < 0.05) and showed higher levels when compared to the placebo group (p < 0.05). Daily muscle connective protein synthesis rates during the intervention period exceeded myofibrillar protein synthesis rates (1.99 ± 0.38 versus 1.34 ± 0.23 %/d, respectively; p < 0.001). Collagen peptide supplementation did not result in higher myofibrillar or muscle connective protein synthesis rates (1.34 ± 0.19 and 1.97 ± 0.47 %/d, respectively) when compared to the placebo group (1.34 ± 0.27 and 2.00 ± 0.27 %/d, respectively; p > 0.05). Collagen peptide supplementation (2 x 15 g daily) does not increase myofibrillar or muscle connective protein synthesis rates during one week of intense resistance exercise training in young, recreational athletes.

Mitochondrial bioenergetics are not associated with myofibrillar protein synthesis rates.

Mitochondria represent key organelles influencing cellular homeostasis and have been implicated in the signalling events regulating protein synthesis. 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±4years, 23.4±3.3kg/m2) and following 12weeks of resistance-type exercise training: n=10 healthy older men (70±3years, 25.2±2.1kg/m2). 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). Neither oxidative phosphorylation nor H2O2 emission were associated with muscle protein synthesis rates in healthy young men under free-living conditions or following 1week 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). 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.

Revised contraindications for the use of non-medical WB-electromyostimulation. Evidence-based German consensus recommendations.

Whole-body electromyostimulation has proven to be a highly effective alternative to conventional resistance-type exercise training. However, due to adverse effects in the past, very extensive contraindications have been put in place for the commercial, non-medical WB-EMS market. Considering recent positive innovations e.g., federal regulation, mandatory trainer education, revised guidelines, and new scientific studies on WB-EMS application, we believe that a careful revision of the very restrictive contraindications on WB-EMS is needed. This applies all the more because many cohorts with limited options for conventional exercise have so far been excluded. During a first meeting of an evidence-based consensus process, stakeholders from various backgrounds (e.g., research, education, application) set the priorities for revising the contraindications. We decided to focus on four categories of absolute contraindications: "Arteriosclerosis, arterial circulation disorders", "Diabetes mellitus" (DM), "Tumor and cancer" (TC), "Neurologic diseases, neuronal disorders, epilepsy". Based on scientific studies, quality criteria, safety aspects and benefit/risk assessment of the category, DM and TC were moved to the relative contraindication catalogue, while arteriosclerosis/arterial circulation disorders and neurologic diseases/neuronal disorders/epilepsy were still considered as absolute contraindications. While missing evidence suggests maintaining the status of neurologic diseases/neuronal disorders as an absolute contraindication, the risk/benefit-ratio does not support the application of WB-EMS in people with arteriosclerosis/arterial circulation diseases. Despite these very cautious modifications, countries with less restrictive structures for non-medical WB-EMS should consider our approach critically before implementing the present revisions. Considering further the largely increased amount of WB-EMS trials we advice regular updates of the present contraindication list.

The Resistance Training Effects on Skeletal Muscle Stem Cells in Older Adult: A Systematic Review and Meta-Analysis.

The objective of this systematic review and meta-analysis is to examine the effects of resistance exercise training on muscle stem cells in older adults. A database search was performed (PubMed, Scopus, Web of Science and Google Scholar) to identify controlled clinical trials in English language. The mean difference (MD) with 95% confidence intervals (CIs) and overall effect size were calculated for all comparisons. The PEDro scale was used to assess the methodological quality. Nineteen studies were included in the review. The meta-analysis found a significant effect of resistance training (RT) on muscle stem cells in the elderly (difference in means=-0.008, Z=-3.415, P=0.001). Also, muscle stem cells changes were similar in men and women (difference in means=-0.004, Z=-1.558, P=0.119) and significant changes occur in type II muscle fibers (difference in means=-0.017, Z=-7.048, P=0.000). Resistance-type exercise training significantly increased muscle stem cells content in intervention group that this result is similar in men and womenthis increase occurred more in type II muscle fibers.

Myofibrillar protein synthesis rates are increased in chronically exercised skeletal muscle despite decreased anabolic signaling

The molecular responses to acute resistance exercise are well characterized. However, how cellular signals change over time to modulate chronic adaptations to more prolonged exercise training is less well understood. We investigated anabolic signaling and muscle protein synthesis rates at several time points after acute and chronic eccentric loading. Adult rat tibialis anterior muscle was stimulated for six sets of ten repetitions, and the muscle was collected at 0 h, 6 h, 18 h and 48 h. In the last group of animals, 48 h after the first exercise bout a second bout was conducted, and the muscle was collected 6 h later (54 h total). In a second experiment, rats were exposed to four exercise sessions over the course of 2 weeks. Anabolic signaling increased robustly 6 h after the first bout returning to baseline between 18 and 48 h. Interestingly, 6 h after the second bout mTORC1 activity was significantly lower than following the first bout. In the chronically exercised rats, we found baseline anabolic signaling was decreased, whereas myofibrillar protein synthesis (MPS) was substantially increased, 48 h after the last bout of exercise. The increase in MPS occurred in the absence of changes to muscle fiber size or mass. In conclusion, we find that anabolic signaling is already diminished after the second bout of acute resistance type exercise. Further, chronic exposure to resistance type exercise training results in decreased basal anabolic signaling but increased overall MPS rates.

Daily protein-polyphenol ingestion increases daily myofibrillar protein synthesis rates and promotes early muscle functional gains during resistance training.

Factors underpinning the time-course of resistance-type exercise training (RET) adaptations are not fully understood. This study hypothesized that consuming a twice-daily protein-polyphenol beverage (PPB; n = 15; age, 24 ± 1 yr; BMI, 22.3 ± 0.7 kg·m-2) previously shown to accelerate recovery from muscle damage and increase daily myofibrillar protein synthesis (MyoPS) rates would accelerate early (10 sessions) improvements in muscle function and potentiate quadriceps volume and muscle fiber cross-sectional area (fCSA) following 30 unilateral RET sessions in healthy, recreationally active, adults. Versus isocaloric placebo (PLA; n = 14; age, 25 ± 2 yr; BMI, 23.9 ± 1.0 kg·m-2), PPB increased 48 h MyoPS rates after the first RET session measured using deuterated water (2.01 ± 0.15 vs. 1.51 ± 0.16%·day-1, respectively; P < 0.05). In addition, PPB increased isokinetic muscle function over 10 sessions of training relative to the untrained control leg (%U) from 99.9 ± 1.8 pretraining to 107.2 ± 2.4%U at session 10 (vs. 102.6 ± 3.9 to 100.8 ± 2.4%U at session 10 in PLA; interaction P < 0.05). Pre to posttraining, PPB increased type II fCSA (PLA: 120.8 ± 8.2 to 109.5 ± 8.6%U; PPB: 92.8 ± 6.2 to 108.4 ± 9.7%U; interaction P < 0.05), but the gain in quadriceps muscle volume was similar between groups. Similarly, PPB did not further increase peak isometric torque, muscle function, or MyoPS measured posttraining. This suggests that although PPB increases MyoPS and early adaptation, it may not influence longer term adaptations to unilateral RET.NEW & NOTEWORTHY Using a unilateral model of resistance training, we show for the first time that a protein-polyphenol beverage increases initial rates of myofibrillar protein synthesis and promotes early functional improvements. Following a prolonged period of training, this strategy also increases type II fiber hypertrophy and causes large individual variation in gains in quadricep muscle cross-sectional area.

Understanding the effects of nutrition and post-exercise nutrition on skeletal muscle protein turnover: Insights from stable isotope studies

Understanding the effects of nutrition and post-exercise nutrition on skeletal muscle protein turnover: Insights from stable isotope studies

Age-specific Resistance-type Exercise Training Improves Performance Without Altering Strain-injury Susceptibility

PURPOSE: Two tenets of exercise programming/training are injury prevention and performance enhancement. The purpose of this study was to determine whether a validated model of resistance-type exercise training (RTET) utilizing stretch-shortening contractions (SSCs) could alter susceptibility to the mechanical induction of skeletal muscle strain injury with aging. METHODS: F344xBN rats’ dorsiflexor muscles were SSC RTET in vivo for 1 month on a custom-built isokinetic rodent dynamometer utilizing age-specific RTET protocols. Performance for dorsiflexor muscles were analyzed temporally, and immediately following skeletal muscle strain injury. ANOVA was used for statistical analysis; α was set at p < 0.05. RESULTS: Rodents receiving no SSC RTET prior to injury had significant static (-48.6% and -54.5%, respectively) and dynamic (-40.9% and -49.8%, respectively) peak force deficits. Age-specific, SSC RTET improved muscle performance in young and old rodents by 15% and 18%, respectively (p < 0.05). Interestingly, young and old rodents undergoing SSC RTET still incurred significant static (-48.8% and -55.7%, respectively) and dynamic (-47.5% and -48.7%, respectively) peak force deficits, which were similar deficits compared to untrained rodents. CONCLUSIONS: Although age-specific SSC RTET increases skeletal muscle adaptation, these results suggest that skeletal muscle strain induction susceptibility is unaltered following SSC RTET, irrespective of age.

Postexercise cooling impairs muscle protein synthesis rates in recreational athletes.

Key points Protein ingestion and cooling are strategies employed by athletes to improve postexercise recovery and, as such, to facilitate muscle conditioning. However, whether cooling affects postprandial protein handling and subsequent muscle protein synthesis rates during recovery from exercise has not been assessed.We investigated the effect of postexercise cooling on the incorporation of dietary protein‐derived amino acids into muscle protein and acute postprandial (hourly) as well as prolonged (daily) myofibrillar protein synthesis rates during recovery from resistance‐type exercise over 2 weeks.Cold‐water immersion during recovery from resistance‐type exercise lowers the capacity of the muscle to take up and/or direct dietary protein‐derived amino acids towards de novo myofibrillar protein accretion. In addition, cold‐water immersion during recovery from resistance‐type exercise lowers myofibrillar protein synthesis rates during prolonged resistance‐type exercise training.Individuals aiming to improve skeletal muscle conditioning should reconsider applying cooling as a part of their postexercise recovery strategy. We measured the impact of postexercise cooling on acute postprandial (hourly) as well as prolonged (daily) myofibrillar protein synthesis rates during adaptation to resistance‐type exercise over 2 weeks. Twelve healthy males (aged 21 ± 2 years) performed a single resistance‐type exercise session followed by water immersion of both legs for 20 min. One leg was immersed in cold water (8°C: CWI), whereas the other leg was immersed in thermoneutral water (30°C: CON). After water immersion, a beverage was ingested containing 20 g of intrinsically (l‐[1‐13C]‐phenylalanine and l‐[1‐13C]‐leucine) labelled milk protein with 45 g of carbohydrates. In addition, primed continuous l‐[ring‐2H5]‐phenylalanine and l‐[1‐13C]‐leucine infusions were applied, with frequent collection of blood and muscle samples to assess myofibrillar protein synthesis rates in vivo over a 5 h recovery period. In addition, deuterated water (2H2O) was applied with the collection of saliva, blood and muscle biopsies over 2 weeks to assess the effects of postexercise cooling with protein intake on myofibrillar protein synthesis rates during more prolonged resistance‐type exercise training (thereby reflecting short‐term training adaptation). Incorporation of dietary protein‐derived l‐[1‐13C]‐phenylalanine into myofibrillar protein was significantly lower in CWI compared to CON (0.016 ± 0.006 vs. 0.021 ± 0.007 MPE; P = 0.016). Postexercise myofibrillar protein synthesis rates were lower in CWI compared to CON based upon l‐[1‐13C]‐leucine (0.058 ± 0.011 vs. 0.072 ± 0.017% h−1, respectively; P = 0.024) and l‐[ring‐2H5]‐phenylalanine (0.042 ± 0.009 vs. 0.053 ± 0.013% h−1, respectively; P = 0.025). Daily myofibrillar protein synthesis rates assessed over 2 weeks were significantly lower in CWI compared to CON (1.48 ± 0.17 vs. 1.67 ± 0.36% day−1, respectively; P = 0.042). Cold‐water immersion during recovery from resistance‐type exercise reduces myofibrillar protein synthesis rates and, as such, probably impairs muscle conditioning.

Post-exercise Cooling Impairs Muscle Protein Synthesis Rates In Healthy Young Males

Protein ingestion and cooling are strategies employed by athletes to improve post-exercise recovery and, as such, to facilitate muscle reconditioning following exercise. However, whether post-exercise cooling affects postprandial protein handling and subsequent muscle protein synthesis rates during recovery from exercise has not been studied. PURPOSE: This study assessed the impact of post-exercise cooling on acute postprandial (hourly) and prolonged (daily) myofibrillar protein synthesis rates during recovery from resistance-type exercise over a 2-week period. METHODS: Twelve healthy, male adults (age: 21±1 y) performed a single session of resistance-type exercise followed by water immersion of both legs for 20 min. One leg was immersed in cold water (8°C: CWI) while the other leg was immersed in thermoneutral water (30°C: CON). After water immersion, a beverage was ingested containing 20 g intrinsically L-[1-13C]-phenylalanine and L-[1-13C]-leucine labelled milk protein with 45 g of carbohydrates. In addition, primed continuous L-[ring-2H5]-phenylalanine and L-[1-13C]-leucine infusions were applied, with frequent collection of blood samples and muscle biopsies to assess myofibrillar protein synthesis rates in vivo over a 5-h recovery period. In addition, deuterated water (2H2O) was ingested with the collection of saliva, blood and muscle biopsies over 2 weeks to assess the effects of post-exercise cooling with protein intake on myofibrillar protein synthesis rates during more prolonged resistance-type exercise training. RESULTS: Incorporation of dietary protein-derived L-[1-13C]-phenylalanine into myofibrillar protein was significantly lower in CWI compared to CON (0.016±0.002 vs 0.021±0.002 MPE; P=0.016). Post-exercise myofibrillar protein synthesis rates were lower in CWI compared to CON based upon L-[1-13C]-leucine (0.058±0.003 vs 0.072±0.005%·h-1, respectively; P=0.024) and L-[ring-2H5]-phenylalanine (0.042±0.003 vs 0.053±0.004%·h-1, respectively; P=0.025). Daily myofibrillar protein synthesis rates assessed over 2 weeks were significantly lower in CWI when compared to CON (1.48±0.05 vs 1.67±0.11%·d-1, respectively; P=0.042). CONCLUSION: Cold-water immersion during recovery from resistance-type exercise impairs myofibrillar protein synthesis rates.

Muscle mass and strength gains following 6 months of resistance type exercise training are only partly preserved within one year with autonomous exercise continuation in older adults.

Although resistance type exercise training (RT) effectively increases muscle mass and strength in older individuals, it remains unclear whether gains in muscle mass and strength are maintained without continued supervised training. We assessed the capacity of older individuals to maintain muscle mass and strength gains one year after partaking in a successful RT program. Fifty-three healthy older adults performed a 24-wk supervised RT program. Upon the cessation of the training program, participants were not provided with any advice or incentives to continue exercise training. One year after completion of the training program, all participants were contacted and invited back to the laboratory to assess anthropometrics, body composition (DXA), quadriceps muscle cross-sectional area (CSA) (CT-scan), muscle strength (1RM knee extension/leg press), and muscle fiber characteristics (muscle biopsy). Following primary analyses on all participants that responded to the invitation (n = 35), participants were divided into two groups: individuals who had continued to perform exercise training on an individual basis (EXER group; n = 16) and individuals who had not continued to perform any regular exercise (STOP group; n = 19) after completing the RT program. The initial increases in quadriceps CSA (+506 ± 209 and +584 ± 287 mm2) and knee extension strength (+32 ± 12 vs +34 ± 10 kg) after the 24-wk RT program did not differ between the STOP and EXER group (all P > 0.05). One year after discontinuation of the RT program, participants had lost muscle mass (P < 0.01), with a greater decline in quadriceps CSA in the STOP vs EXER group (-579 ± 268 vs -309 ± 253 mm2, respectively; P < 0.05). Muscle strength had decreased significantly compared to values after completing the RT program (P < 0.01), with no differences observed between the STOP vs EXER group (knee extension: -21 ± 8 vs -18 ± 8 kg, respectively; P > 0.05), yet remained higher compared with values before the RT program (P < 0.05). Though prolonged RT can effectively increase muscle mass and strength in the older population, muscle mass gains are lost and muscle strength gains are only partly preserved within one year if the supervised exercise program is not continued.

The Impact of Pre-sleep Protein Ingestion on the Skeletal Muscle Adaptive Response to Exercise in Humans: An Update.

This review provides an update on recent research assessing the effect of pre-sleep protein ingestion on muscle protein synthesis rates during overnight sleep and the skeletal muscle adaptive response to exercise training. Protein ingested prior to sleep is effectively digested and absorbed during overnight sleep, thereby increasing overnight muscle protein synthesis rates. Protein consumption prior to sleep does not appear to reduce appetite during breakfast the following day and does not change resting energy expenditure. When applied over a prolonged period of resistance-type exercise training, pre-sleep protein supplementation has a beneficial effect on the increase in muscle mass and strength. Protein ingestion before sleep is hypothesized to represent an effective nutritional strategy to preserve muscle mass in the elderly, especially when combined with physical activity or muscle contraction by means of neuromuscular electrical stimulation. In conclusion, protein ingestion prior to sleep is an effective interventional strategy to increase muscle protein synthesis rates during overnight sleep and can be applied to support the skeletal muscle adaptive response to resistance-type exercise training.

Reduced frequency of resistance-type exercise training promotes adaptation of the aged skeletal muscle microenvironment.

The purpose of this study was to characterize the growth and remodeling molecular signaling response in aged skeletal muscle following 1 mo of "resistance-type exercise" training. Male Fischer 344 × Brown Norway hybrid rats aged 3 (young) and 30 mo (old) underwent stretch-shortening contraction (SSC) loading 2 or 3 days/wk; muscles were removed 72 h posttraining. Young rats SSC loaded 3 (Y3x) or 2 days/wk (Y2x) adapted via increased work performance. Old rats SSC loaded 3 days/wk (O3x) maladapted via decreased negative work; however, old rats SSC loaded 2 days/wk (O2x) adapted through improved negative and positive work. Y3x, Y2x, and O2x, but not O3x, displayed hypertrophy via larger fiber area and myonuclear domains. Y3x, Y2x, and O2x differentially expressed 19, 30, and 8 phosphatidylinositol 3-kinase-Akt genes, respectively, whereas O3x only expressed 2. Bioinformatics analysis revealed that rats in the adapting groups presented growth and remodeling processes (i.e., increased protein synthesis), whereas O3x demonstrated inflammatory signaling. In conclusion, reducing SSC-loading frequency in aged rodents positively influences the molecular signaling microenvironment, promoting muscle adaptation. NEW & NOTEWORTHY Decreasing resistance-type exercise training frequency in old rodents led to adaptation through enhancements in performance, fiber areas, and myonuclear domains. Modifying frequency influenced the molecular environment through improvements in phosphatidylinositol 3-kinase-Akt pathway-specific expression and bioinformatics indicating increased protein synthesis. Reducing training frequency may be appropriate in older individuals who respond unfavorably to higher frequencies (i.e., maladaptation); overall, modifying the parameters of the exercise prescription can affect the cellular environment, ultimately leading to adaptive or maladaptive outcomes.

Leucine-Enriched Protein Supplementation Does Not Augment Muscle Mass and Strength Gains During Resistance-Type Exercise Training in Older Males

Leucine-Enriched Protein Supplementation Does Not Augment Muscle Mass and Strength Gains During Resistance-Type Exercise Training in Older Males

Effects Of 6-week Resistance-type Exercise Training On Serum 25-hydroxyvitamin D Concentrations In Young Men

Effects Of 6-week Resistance-type Exercise Training On Serum 25-hydroxyvitamin D Concentrations In Young Men

Daily resistance-type exercise stimulates muscle protein synthesis in vivo in young men.

Resistance-type exercise increases muscle protein synthesis rates during acute postexercise recovery. The impact of resistance-type exercise training on (local) muscle protein synthesis rates under free-living conditions on a day-to-day basis remains unclear. We determined the impact of daily unilateral resistance-type exercise on local myofibrillar protein synthesis rates during a 3-day period. Twelve healthy young men (22 ± 1 yr) were recruited to participate in this study where they performed daily, unilateral resistance-type exercise during a 3-day intervention period. Two days before the exercise training subjects ingested 400 ml deuterated water (2H2O). Additional 50-ml doses of deuterated water were ingested daily during the training period. Saliva and blood samples were collected daily to assess body water and amino acid precursor deuterium enrichments, respectively. Muscle tissue biopsies were collected before and after the 3 days of unilateral resistance-type exercise training from both the exercised and the nonexercised, control leg for the assessment of muscle protein synthesis rates. Deuterated water dosing resulted in a steady-state body water enrichment of 0.70 ± 0.03%. Intramuscular free [2H]alanine enrichment increased up to 1.84 ± 0.06 mole percent excess (MPE) before the exercise training and did not change in both the exercised and control leg during the 3 subsequent exercise training days (2.11 ± 0.11 and 2.19 ± 0.12 MPE, respectively; P > 0.05). Muscle protein synthesis rates averaged 1.984 ± 0.118 and 1.642 ± 0.089%/day in the exercised vs. nonexercised, control leg when assessed over the entire 3-day period ( P < 0.05). Daily resistance-type exercise stimulates (local) muscle protein synthesis in vivo in humans. NEW & NOTEWORTHY This study demonstrates that daily resistance-type exercise stimulates muscle protein synthesis rates in vivo in humans over multiple days. Whereas acute studies have shown that resistance-type exercise increases muscle protein synthesis rates by 50-100%, we observed a lower impact of resistance-type exercise under free-living conditions. We also compared precursor tracer selection for the calculation of muscle protein synthesis rates and observed that saliva deuterium enrichment serves as an appropriate and practical choice of precursor.

Protein Supplementation Augments Muscle Fiber Hypertrophy but Does Not Modulate Satellite Cell Content During Prolonged Resistance-Type Exercise Training in Frail Elderly

ObjectiveProtein supplementation increases gains in lean body mass following prolonged resistance-type exercise training in frail older adults. We assessed whether the greater increase in lean body mass can be attributed to muscle fiber type specific hypertrophy with concomitant changes in satellite cell (SC) content. DesignA total of 34 frail elderly individuals (77 ± 1 years, n = 12 male adults) participated in this randomized, double-blind, placebo-controlled trial with 2 arms in parallel. InterventionParticipants performed 24 weeks of progressive resistance-type exercise training (2 sessions per week) during which they were supplemented twice-daily with milk protein (2 × 15 g) or a placebo. MethodsMuscle biopsies were taken at baseline, and after 12 and 24 weeks of intervention, to determine type I and type II muscle fiber specific cross-sectional area (CSA), SC content, and myocellular characteristics. ResultsIn the placebo group, a trend for a 20% ± 11% increase in muscle fiber CSA was observed in type II fibers only (P = .051), with no increase in type I muscle fiber CSA. In the protein group, type I and II muscle fiber CSA increased by 23% ± 7% and 34% ± 10% following 6 months of training, respectively (P < .01). Myonuclear domain size increased over time in both groups and fiber types (P < .001), with no significant differences between groups (P > .05). No changes in myonuclear content and SC contents were observed over time in either group (both P > .05). Regression analysis showed that changes in myonuclear content and domain size are predictive of muscle fiber hypertrophy. ConclusionsProtein supplementation augments muscle fiber hypertrophy following prolonged resistance-type exercise training in frail older people, without changes in myonuclear and SC content.

Pre-Sleep Protein Ingestion to Improve the Skeletal Muscle Adaptive Response to Exercise Training.

Protein ingestion following resistance-type exercise stimulates muscle protein synthesis rates, and enhances the skeletal muscle adaptive response to prolonged resistance-type exercise training. As the adaptive response to a single bout of resistance exercise extends well beyond the first couple of hours of post-exercise recovery, recent studies have begun to investigate the impact of the timing and distribution of protein ingestion during more prolonged recovery periods. Recent work has shown that overnight muscle protein synthesis rates are restricted by the level of amino acid availability. Protein ingested prior to sleep is effectively digested and absorbed, and thereby stimulates muscle protein synthesis rates during overnight recovery. When applied during a prolonged period of resistance-type exercise training, protein supplementation prior to sleep can further augment gains in muscle mass and strength. Recent studies investigating the impact of pre-sleep protein ingestion suggest that at least 40 g of protein is required to display a robust increase in muscle protein synthesis rates throughout overnight sleep. Furthermore, prior exercise allows more of the pre-sleep protein-derived amino acids to be utilized for de novo muscle protein synthesis during sleep. In short, pre-sleep protein ingestion represents an effective dietary strategy to improve overnight muscle protein synthesis, thereby improving the skeletal muscle adaptive response to exercise training.

Resistance Training Increases Skeletal Muscle Capillarization in Healthy Older Men.

Skeletal muscle capillarization plays a key role in oxygen and nutrient delivery to muscle. The loss of muscle mass with aging and the concept of anabolic resistance have been, at least partly, attributed to changes in skeletal muscle capillary structure and function. We aimed to compare skeletal muscle capillarization between young and older men and evaluate whether resistance-type exercise training increases muscle capillarization in older men. Muscle biopsies were obtained from the vastus lateralis of healthy young (n = 14, 26 ± 2 yr) and older (n = 16, 72 ± 1 yr) adult men, with biopsies before and after 12 wk of resistance-type exercise training in the older subjects. Immunohistochemistry was used to assess skeletal muscle fiber size, capillary contacts (CC) per muscle fiber, and the capillary-to-fiber perimeter exchange (CFPE) index in type I and II muscle fibers. Type II muscle fibers were smaller in old versus young (4507 ± 268 vs 6084 ± 497 μm, respectively, P = 0.007). Type I and type II muscle fiber CC and CFPE index were smaller in old compared with young muscle (CC type I: 3.8 ± 0.2 vs 5.0 ± 0.3; CC type II: 3.2 ± 0.2 vs 4.2 ± 0.2, respectively; both P < 0.001). Resistance-type exercise training increased type II muscle fiber size only. In addition, CC and CFPE index increased in both the type I (26% ± 9% and 27% ± 8%) and type II muscle fibers (33% ± 7% and 24% ± 6%, respectively; all P ≤ 0.001) after 12 wk resistance training in older men. We conclude that resistance-type exercise training can effectively augment skeletal muscle fiber capillarization in older men. The greater capillary supply may be an important prerequisite to reverse anabolic resistance and support muscle hypertrophy during lifestyle interventions aiming to support healthy aging.

Muscle fibre capillarization is a critical factor in muscle fibre hypertrophy during resistance exercise training in older men.

BackgroundAdequate muscle fibre perfusion is critical for the maintenance of muscle mass; it is essential in the rapid delivery of oxygen, nutrients and growth factors to the muscle, stimulating muscle fibre growth. Muscle fibre capillarization is known to decrease substantially with advancing age. However, whether (relative) low muscle fibre capillarization negatively impacts the muscle hypertrophic response following resistance exercise training in older adults is unknown.MethodsTwenty‐two healthy older men (71 ± 1 years) performed 24 weeks of progressive resistance type exercise training. To assess the change in muscle fibre characteristics, percutaneous biopsies from the vastus lateralis muscle were taken before and following 12 and 24 weeks of the intervention programme. A comparison was made between participants who had a relatively low type II muscle fibre capillary‐to‐fibre perimeter exchange index (CFPE; LOW group) and high type II muscle fibre CFPE (HIGH group) at baseline. Type I and type II muscle fibre size, satellite cell, capillary content and distance between satellite cells to the nearest capillary were determined by immunohistochemistry.ResultsOverall, type II muscle fibre size (from 5150 ± 234 to 6719 ± 446 µm2, P < 0.05) and satellite cell content (from 0.058 ± 0.006 to 0.090 ± 0.010 satellite cells per muscle fibre, P < 0.05) had increased significantly in response to 24 weeks of resistance exercise training. However, these improvements where mainly driven by differences in baseline type II muscle fibre capillarization, whereas muscle fibre size (from 5170 ± 390 to 7133 ± 314 µm2, P < 0.05) and satellite cell content (from 0.059 ± 0.009 to 0.102 ± 0.017 satellite cells per muscle fibre, P < 0.05) increased significantly in the HIGH group, no significant changes were observed in LOW group following exercise training. No significant changes in type I and type II muscle fibre capillarization were observed in response to 12 and 24 weeks of resistance exercise training in both the LOW and HIGH group.ConclusionsType II muscle fibre capillarization at baseline may be a critical factor for allowing muscle fibre hypertrophy to occur during prolonged resistance exercise training in older men.