Prolonged Resistance-type Exercise Training Research Articles

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

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.

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.

Expression of protocadherin gamma in skeletal muscle tissue is associated with age and muscle weakness

BackgroundThe skeletal muscle system plays an important role in the independence of older adults. In this study we examine differences in the skeletal muscle transcriptome between healthy young and older subjects and (pre‐)frail older adults. Additionally, we examine the effect of resistance‐type exercise training on the muscle transcriptome in healthy older subjects and (pre‐)frail older adults.MethodsBaseline transcriptome profiles were measured in muscle biopsies collected from 53 young, 73 healthy older subjects, and 61 frail older subjects. Follow‐up samples from these frail older subjects (31 samples) and healthy older subjects (41 samples) were collected after 6 months of progressive resistance‐type exercise training. Frail older subjects trained twice per week and the healthy older subjects trained three times per week.ResultsAt baseline genes related to mitochondrial function and energy metabolism were differentially expressed between older and young subjects, as well as between healthy and frail older subjects. Three hundred seven genes were differentially expressed after training in both groups. Training affected expression levels of genes related to extracellular matrix, glucose metabolism ,and vascularization. Expression of genes that were modulated by exercise training was indicative of muscle strength at baseline. Genes that strongly correlated with strength belonged to the protocadherin gamma gene cluster (r = −0.73).ConclusionsOur data suggest significant remaining plasticity of ageing skeletal muscle to adapt to resistance‐type exercise training. Some age‐related changes in skeletal muscle gene expression appear to be partially reversed by prolonged resistance‐type exercise training. The protocadherin gamma gene cluster may be related to muscle denervation and re‐innervation in ageing muscle.

The Muscle Metabolome Differs between Healthy and Frail Older Adults.

Populations around the world are aging rapidly. Age-related loss of physiological functions negatively affects quality of life. A major contributor to the frailty syndrome of aging is loss of skeletal muscle. In this study we assessed the skeletal muscle biopsy metabolome of healthy young, healthy older and frail older subjects to determine the effect of age and frailty on the metabolic signature of skeletal muscle tissue. In addition, the effects of prolonged whole-body resistance-type exercise training on the muscle metabolome of older subjects were examined. The baseline metabolome was measured in muscle biopsies collected from 30 young, 66 healthy older subjects, and 43 frail older subjects. Follow-up samples from frail older (24 samples) and healthy older subjects (38 samples) were collected after 6 months of prolonged resistance-type exercise training. Young subjects were included as a reference group. Primary differences in skeletal muscle metabolite levels between young and healthy older subjects were related to mitochondrial function, muscle fiber type, and tissue turnover. Similar differences were observed when comparing frail older subjects with healthy older subjects at baseline. Prolonged resistance-type exercise training resulted in an adaptive response of amino acid metabolism, especially reflected in branched chain amino acids and genes related to tissue remodeling. The effect of exercise training on branched-chain amino acid-derived acylcarnitines in older subjects points to a downward shift in branched-chain amino acid catabolism upon training. We observed only modest correlations between muscle and plasma metabolite levels, which pleads against the use of plasma metabolites as a direct read-out of muscle metabolism and stresses the need for direct assessment of metabolites in muscle tissue biopsies.

Changes in myonuclear domain size do not precede muscle hypertrophy during prolonged resistance-type exercise training.

Muscle fibre hypertrophy is accompanied by an increase in myonuclear number, an increase in myonuclear domain size or both. It has been suggested that increases in myonuclear domain size precede myonuclear accretion and subsequent muscle fibre hypertrophy during prolonged exercise training. In this study, we assessed the changes in muscle fibre size, myonuclear and satellite cell content throughout 12weeks of resistance-type exercise training in young men. Twenty-two young men (23±1year) were assigned to a progressive, 12-weeks resistance-type exercise training programme (3sessions per week). Muscle biopsies from the vastus lateralis muscle were taken before and after 2, 4, 8 and 12weeks of exercise training. Muscle fibre size, myonuclear content, myonuclear domain size and satellite cell content were assessed by immunohistochemistry. Type I and type II muscle fibre size increased gradually throughout the 12weeks of training (type I: 18±5%, type II: 41±6%, P<0.01). Myonuclear content increased significantly over time in both the type I (P<0.01) and type II (P<0.001) muscle fibres. No changes in type I and type II myonuclear domain size were observed at any time point throughout the intervention. Satellite cell content increased significantly over time in both type I and type II muscle fibres (P<0.001). Increases in myonuclear domain size do not appear to drive myonuclear accretion and muscle fibre hypertrophy during prolonged resistance-type exercise training invivo in humans.

Protein Ingestion before Sleep Increases Muscle Mass and Strength Gains during Prolonged Resistance-Type Exercise Training in Healthy Young MenNitrogen1–3

Background: It has been demonstrated that protein ingestion before sleep increases muscle protein synthesis rates during overnight recovery from an exercise bout. However, it remains to be established whether dietary protein ingestion before sleep can effectively augment the muscle adaptive response to resistance-type exercise training.Objective: Here we assessed the impact of dietary protein supplementation before sleep on muscle mass and strength gains during resistance-type exercise training.Methods: Forty-four young men (22 ± 1 y) were randomly assigned to a progressive, 12-wk resistance exercise training program. One group consumed a protein supplement containing 27.5 g of protein, 15 g of carbohydrate, and 0.1 g of fat every night before sleep. The other group received a noncaloric placebo. Muscle hypertrophy was assessed on a whole-body (dual-energy X-ray absorptiometry), limb (computed tomography scan), and muscle fiber (muscle biopsy specimen) level before and after exercise training. Strength was assessed regularly by 1-repetition maximum strength testing.Results: Muscle strength increased after resistance exercise training to a significantly greater extent in the protein-supplemented (PRO) group than in the placebo-supplemented (PLA) group (+164 ± 11 kg and +130 ± 9 kg, respectively; P < 0.001). In addition, quadriceps muscle cross-sectional area increased in both groups over time (P < 0.001), with a greater increase in the PRO group than in the PLA group (+8.4 ± 1.1 cm2 vs. +4.8 ± 0.8 cm2, respectively; P < 0.05). Both type I and type II muscle fiber size increased after exercise training (P < 0.001), with a greater increase in type II muscle fiber size in the PRO group (+2319 ± 368 μm2) than in the PLA group (+1017 ± 353 μm2; P < 0.05).Conclusion: Protein ingestion before sleep represents an effective dietary strategy to augment muscle mass and strength gains during resistance exercise training in young men. This trial was registered at http://www.w3.org/1999/xlink as NCT02222415.

Large Heterogeneity In The Responsiveness To Resistance-type Exercise Training In The Older Population

Ageing is associated with a decline in skeletal muscle mass, strength, and physical function. Resistance-type exercise is an effective interventional strategy to increase skeletal muscle mass and strength, however the adaptive response to exercise is remarkably heterogeneous. As small subsets of individual subjects sometimes show no increase or even a decline in muscle mass, it has been suggested that some older individuals may be unresponsive to the benefits of exercise. PURPOSE: To examine the heterogeneity in resistance-type exercise training induced changes in lean body mass (LBM), strength, and physical function in a large sample of older men and women. METHODS: Older subjects (>65 y) were selected to participate in 3 (n = 110) to 6 (n = 85) months of supervised resistance-type exercise training. Changes in LBM (DXA), leg strength (1-RM on leg press and leg extension), and physical function (chair rise-time) were assessed at baseline, and after 3 and 6 months of resistance-type training. RESULTS: LBM increased by 0.7±0.1 kg at 3 months, with individual data ranging from -3.8 to 5.4 kg. By 6 months, LBM increased by 1.1±0.2 kg, with individual data ranging from -1.8 to 9.2 kg. Leg press and leg extension strength increased by 33±2 and 20±1 kg at 3 months, with individual data ranging from -36 to 87 and -22 to 56 kg. At 6 months, leg strength had increased by 50±3 and 29±2 kg on the leg press and leg extension, with individual data ranging from -28 to 145 kg and -19 to 60 kg, respectively. Chair rise-time decreased by 1.3±0.4 s at 3 months, with individual data ranging from -12.5 to 21.6 s. At 6 months, chair rise-time had decreased by 2.3±0.4 s, with individual data ranging from -23 to 10.5 s. CONCLUSIONS: A large heterogeneity exists in the adaptive response to prolonged resistance-type exercise training in the older population. However, non-responsiveness was not apparent in any subject, as positive changes on one or more outcome measures (LBM, strength and physical function) were evident in all subjects. Furthermore, the magnitude of responsiveness was impacted by the duration of training, with more positive responders at 6 vs 3 months. We conclude that there are no non-responders to the benefits of resistance-type exercise training. Resistance-type exercise should be prescribed to support healthy aging in the elderly population.

There Are No Nonresponders to Resistance-Type Exercise Training in Older Men and Women

ObjectiveTo assess the proposed prevalence of unresponsiveness of older men and women to augment lean body mass, muscle fiber size, muscle strength, and/or physical function following prolonged resistance-type exercise training. Design/Setting/ParticipantsA retrospective analysis of the adaptive response to 12 (n = 110) and 24 (n = 85) weeks of supervised resistance-type exercise training in older (>65 years) men and women. MeasurementsLean body mass (DXA), type I and type II muscle fiber size (biopsy), leg strength (1-RM on leg press and leg extension), and physical function (chair-rise time) were assessed at baseline, and after 12 and 24 weeks of resistance-type exercise training. ResultsLean body mass increased by 0.9 ± 0.1 kg (range: −3.3 to +5.4 kg; P < .001) from 0 to 12 weeks of training. From 0 to 24 weeks, lean body mass increased by 1.1 ± 0.2 kg (range: −1.8 to +9.2 kg; P < .001). Type I and II muscle fiber size increased by 324 ± 137 μm2 (range: −4458 to +3386 μm2; P = .021), and 701 ± 137 μm2 (range: −4041 to +3904 μm2; P < .001) from 0 to 12 weeks. From 0 to 24 weeks, type I and II muscle fiber size increased by 360 ± 157 μm2 (range: −3531 to +3426 μm2; P = .026) and 779 ± 161 μm2 (range: −2728 to +3815 μm2; P < .001). The 1-RM strength on the leg press and leg extension increased by 33 ± 2 kg (range: −36 to +87 kg; P < .001) and 20 ± 1 kg (range: −22 to +56 kg; P < .001) from 0 to 12 weeks. From 0 to 24 weeks, leg press and leg extension 1-RM increased by 50 ± 3 kg (range: −28 to +145 kg; P < .001) and 29 ± 2 kg (range: −19 to +60 kg; P < .001). Chair-rise time decreased by 1.3 ± 0.4 seconds (range: +21.6 to −12.5 seconds; P = .003) from 0 to 12 weeks. From 0 to 24 weeks, chair-rise time decreased by 2.3 ± 0.4 seconds (range: +10.5 to −23.0 seconds; P < .001). Nonresponsiveness was not apparent in any subject, as a positive adaptive response on at least one training outcome was apparent in every subject. ConclusionsA large heterogeneity was apparent in the adaptive response to prolonged resistance-type exercise training when changes in lean body mass, muscle fiber size, strength, and physical function were assessed in older men and women. The level of responsiveness was strongly affected by the duration of the exercise intervention, with more positive responses following more prolonged exercise training. We conclude that there are no nonresponders to the benefits of resistance-type exercise training on lean body mass, fiber size, strength, or function in the older population. Consequently, resistance-type exercise should be promoted without restriction to support healthy aging in the older population.

Protein Supplementation during Resistance-Type Exercise Training in the Elderly

Resistance training has been well established as an effective treatment strategy to increase skeletal muscle mass and strength in the elderly. We assessed whether dietary protein supplementation can further augment the adaptive response to prolonged resistance-type exercise training in healthy elderly men and women. Healthy elderly men (n = 31, 70 ± 1 yr) and women (n = 29, 70 ± 1 yr) were randomly assigned to a progressive, 24-wk resistance-type exercise training program with or without additional protein supplementation (15 g·d-1). Muscle hypertrophy was assessed on a whole-body Dual-energy X-ray absorptiometry (DXA), limb (computed tomography), and muscle fiber (biopsy) level. Strength was assessed regularly by 1-repetition maximum (RM) strength testing. Functional capacity was assessed with a sit-to-stand and handgrip test. One-RM strength increased by 45% ± 6% versus 40% ± 3% (women) and 41% ± 4% versus 44% ± 3% (men) in the placebo versus protein group, respectively (P < 0.001), with no differences between groups. Leg muscle mass (women, 4% ± 1% vs 3% ± 1%; men, 3% ± 1% vs 3% ± 1%) and quadriceps cross-sectional area (women, 9% ± 1% vs 9% ± 1%; men, 9% ± 1% vs 10% ± 1%) increased similarly in the placebo versus protein groups (P < 0.001). Type II muscle fiber size increased over time in both placebo and protein groups (25% ± 13% vs 30% ± 9% and 23% ± 12% vs 22% ± 10% in the women and men, respectively). Sit-to-stand improved by 18% ± 2% and 19% ± 2% in women and men, respectively (P < 0.001). Prolonged resistance-type exercise training increases skeletal muscle mass and strength, augments functional capacity, improves glycemia and lipidemia, and reduces blood pressure in healthy elderly men and women. Additional protein supplementation (15 g·d-1) does not further increase muscle mass, strength, and/or functional capacity.

The decline in skeletal muscle mass with aging is mainly attributed to a reduction in type II muscle fiber size

BackgroundThe loss of skeletal muscle mass with aging has been attributed to a decline in muscle fiber number and muscle fiber size. ObjectiveTo define to what extent differences in leg muscle cross-sectional area (CSA) between young and elderly men are attributed to differences in muscle fiber size. MethodsQuadriceps muscle CSA and type I and type II muscle fiber size were measured in healthy young (n=25; 23±1y) and older (n=26; 71±1y) men. Subsequently, the older subjects performed 6months of resistance type exercise training, after which measurements were repeated. Differences in quadriceps muscle CSA were compared with differences in type I and type II muscle fiber size. ResultsQuadriceps CSA was substantially smaller in older versus young men (68±2 vs 80±2cm2, respectively; P<0.001). Type II muscle fiber size was substantially smaller in the elderly vs the young (29%; P<0.001), with a tendency of smaller type I muscle fibers (P=0.052). Differences in type II muscle fiber size fully explained differences in quadriceps CSA between groups. Prolonged resistance type exercise training in the elderly increased type II muscle fiber size by 24±8% (P<0.01), explaining 100±3% of the increase in quadriceps muscle CSA (from 68±2 to 74±2cm2). ConclusionReduced muscle mass with aging is mainly attributed to smaller type II muscle fiber size and, as such, is unlikely accompanied by substantial muscle fiber loss. In line, the increase in muscle mass following prolonged resistance type exercise training can be attributed entirely to specific type II muscle fiber hypertrophy.

Protein supplementation augments the adaptive response of skeletal muscle to resistance-type exercise training: a meta-analysis

Protein ingestion after a single bout of resistance-type exercise stimulates net muscle protein accretion during acute postexercise recovery. Consequently, it is generally accepted that protein supplementation is required to maximize the adaptive response of the skeletal muscle to prolonged resistance-type exercise training. However, there is much discrepancy in the literature regarding the proposed benefits of protein supplementation during prolonged resistance-type exercise training in younger and older populations. The objective of the study was to define the efficacy of protein supplementation to augment the adaptive response of the skeletal muscle to prolonged resistance-type exercise training in younger and older populations. A systematic review of interventional evidence was performed through the use of a random-effects meta-analysis model. Data from the outcome variables fat-free mass (FFM), fat mass, type I and II muscle fiber cross-sectional area, and 1 repetition maximum (1-RM) leg press strength were collected from randomized controlled trials (RCTs) investigating the effect of dietary protein supplementation during prolonged (>6 wk) resistance-type exercise training. Data were included from 22 RCTs that included 680 subjects. Protein supplementation showed a positive effect for FFM (weighted mean difference: 0.69 kg; 95% CI: 0.47, 0.91 kg; P < 0.00001) and 1-RM leg press strength (weighted mean difference: 13.5 kg; 95% CI: 6.4, 20.7 kg; P < 0.005) compared with a placebo after prolonged resistance-type exercise training in younger and older subjects. Protein supplementation increases muscle mass and strength gains during prolonged resistance-type exercise training in both younger and older subjects.

Perspective: Protein Supplementation During Prolonged Resistance Type Exercise Training Augments Skeletal Muscle Mass and Strength Gains

Perspective: Protein Supplementation During Prolonged Resistance Type Exercise Training Augments Skeletal Muscle Mass and Strength Gains

Reduced AMPK-ACC and mTOR signaling in muscle from older men, and effect of resistance exercise

AMP-activated protein kinase (AMPK) is a key energy-sensitive enzyme that controls numerous metabolic and cellular processes. Mammalian target of rapamycin (mTOR) is another energy/nutrient-sensitive kinase that controls protein synthesis and cell growth. In this study we determined whether older versus younger men have alterations in the AMPK and mTOR pathways in skeletal muscle, and examined the effect of a long term resistance type exercise training program on these signaling intermediaries. Older men had decreased AMPKα2 activity and lower phosphorylation of AMPK and its downstream signaling substrate acetyl-CoA carboxylase (ACC). mTOR phosphylation also was reduced in muscle from older men. Exercise training increased AMPKα1 activity in older men, however, AMPKα2 activity, and the phosphorylation of AMPK, ACC and mTOR, were not affected. In conclusion, older men have alterations in the AMPK-ACC and mTOR pathways in muscle. In addition, prolonged resistance type exercise training induces an isoform-selective up regulation of AMPK activity.

Protein Supplementation Increases Muscle Mass Gain During Prolonged Resistance-Type Exercise Training in Frail Elderly People: A Randomized, Double-Blind, Placebo-Controlled Trial

Protein supplementation has been proposed as an effective dietary strategy to augment the skeletal muscle adaptive response to prolonged resistance-type exercise training in elderly people. Our objective was to assess the impact of protein supplementation on muscle mass, strength, and physical performance during prolonged resistance-type exercise training in frail elderly men and women. A randomized, double-blind, placebo-controlled trial with 2 arms in parallel among 62 frail elderly subjects (78 ± 1 year). These elderly subjects participated in a progressive resistance-type exercise training program (2 sessions per week for 24 weeks) during which they were supplemented twice daily with either protein (2 * 15 g) or a placebo. Lean body mass (DXA), strength (1-RM), and physical performance (SPPB) were assessed at baseline, and after 12 and 24 weeks of intervention. Lean body mass increased from 47.2 kg (95% CI, 43.5-50.9) to 48.5 kg (95% CI, 44.8-52.1) in the protein group and did not change in the placebo group (from 45.7 kg, 95% CI, 42.1-49.2 to 45.4 kg, 95% CI, 41.8-48.9) following the intervention (P value for treatment × time interaction = .006). Strength and physical performance improved significantly in both groups (P = .000) with no interaction effect of dietary protein supplementation. Prolonged resistance-type exercise training represents an effective strategy to improve strength and physical performance in frail elderly people. Dietary protein supplementation is required to allow muscle mass gain during exercise training in frail elderly people. clinicaltrials.gov identifier: NCT01110369.

PP230-SUN THE EFFECTS OF PROTEIN SUPPLEMENTATION DURING PROLONGED RESISTANCE TYPE EXERCISE TRAINING ON MUSCLE MASS AND FUNCTION IN FRAIL ELDERLY

PP230-SUN THE EFFECTS OF PROTEIN SUPPLEMENTATION DURING PROLONGED RESISTANCE TYPE EXERCISE TRAINING ON MUSCLE MASS AND FUNCTION IN FRAIL ELDERLY

Protein supplementation before and after exercise does not further augment skeletal muscle hypertrophy after resistance training in elderly men

Background:Considerable discrepancy exists in the literature on the proposed benefits of protein supplementation on the adaptive response of skeletal muscle to resistance-type exercise training in the elderly.Objective: The objective was to assess the benefits of timed protein supplementation on the increase in muscle mass and strength during prolonged resistance-type exercise training in healthy elderly men who habitually consume adequate amounts of dietary protein.Design: Healthy elderly men (n = 26) aged 72 ± 2 y were randomly assigned to a progressive, 12-wk resistance-type exercise training program with (protein group) or without (placebo group) protein provided before and immediately after each exercise session (3 sessions/wk, 20 g protein/session). One-repetition maximum (1RM) tests were performed regularly to ensure a progressive workload during the intervention. Muscle hypertrophy was assessed at the whole-body (dual-energy X-ray absorptiometry), limb (computed tomography), and muscle fiber (biopsy) level.Results: The 1RM strength increased ≈25–35% in both groups (P < 0.001). Dual-energy X-ray absorptiometry and computed tomography scans showed similar increases in leg muscle mass (6 ± 1% in both groups; P < 0.001) and in the quadriceps (9 ± 1% in both groups), from 75.9 ± 3.7 and 73.8 ± 3.2 to 82.4 ± 3.9 and 80.0 ± 3.0 cm2 in the placebo and protein groups, respectively (P < 0.001). Muscle fiber hypertrophy was greater in type II (placebo: 28 ± 6%; protein: 29 ± 4%) than in type I (placebo: 5 ± 4%; protein: 13 ± 6%) fibers, but the difference between groups was not significant.Conclusion: Timed protein supplementation immediately before and after exercise does not further augment the increase in skeletal muscle mass and strength after prolonged resistance-type exercise training in healthy elderly men who habitually consume adequate amounts of dietary protein. This trial was registered at clinicaltrials.gov as NCT00744094.

Aging, exercise, and muscle protein metabolism

Aging is accompanied by a progressive loss of skeletal muscle mass and strength, leading to the loss of functional capacity and an increased risk of developing chronic metabolic disease. The age-related loss of skeletal muscle mass is attributed to a disruption in the regulation of skeletal muscle protein turnover, resulting in an imbalance between muscle protein synthesis and degradation. As basal (fasting) muscle protein synthesis rates do not seem to differ substantially between the young and elderly, many research groups have started to focus on the muscle protein synthetic response to the main anabolic stimuli, i.e., food intake and physical activity. Recent studies suggest that the muscle protein synthetic response to food intake is blunted in the elderly. The latter is now believed to represent a key factor responsible for the age-related decline in skeletal muscle mass. Physical activity and/or exercise stimulate postexercise muscle protein accretion in both the young and elderly. However, the latter largely depends on the timed administration of amino acids and/or protein before, during, and/or after exercise. Prolonged resistance type exercise training represents an effective therapeutic strategy to augment skeletal muscle mass and improve functional performance in the elderly. The latter shows that the ability of the muscle protein synthetic machinery to respond to anabolic stimuli is preserved up to very old age. Research is warranted to elucidate the interaction between nutrition, exercise, and the skeletal muscle adaptive response. The latter is needed to define more effective strategies that will maximize the therapeutic benefits of lifestyle intervention in the elderly.