Bout Of Heavy Resistance Exercise Research Articles

Circulating extracellular vesicle characteristics differ between men and women following 12 weeks of concurrent exercise training.

Concurrent resistance and endurance exercise training (CET) has well-studied benefits; however, inherent hormonal and genetic differences alter adaptive responses to exercise between sexes. Extracellular vesicles (EVs) are factors that contribute to adaptive signaling. Our purpose was to test if EV characteristics differ between men and women following CET. 18 young healthy participants underwent 12-weeks of CET. Prior to and following CET, subjects performed an acute bout of heavy resistance exercise (AHRET) consisting of 6 × 10 back squats at 75% 1RM. At rest and following AHRET, EVs were isolated from plasma and characteristics and miRNA contents were analyzed. AHRET elevated EV abundance in trained men only (+51%) and AHRET-induced changes were observed for muscle-derived EVs and microvesicles. There were considerable sex-specific effects of CET on EV miRNAs, highlighted by larger variation following the 12-week program in men compared to women at rest. Pathway analysis based on differentially expressed EV miRNAs predicted that AHRET and 12 weeks of CET in men positively regulates hypertrophy and growth pathways more so than in women. This report highlights sex-based differences in the EV response to resistance and concurrent exercise training and suggests that EVs may be important adaptive signaling factors altered by exercise training.

Age and prior exercise in vivo determine the subsequent in vitro molecular profile of myoblasts and nonmyogenic cells derived from human skeletal muscle.

The decline in skeletal muscle regenerative capacity with age is partly attributed to muscle stem cell (satellite cell) dysfunction. Recent evidence has pointed to a strong interaction between myoblasts and fibroblasts, but the influence of age on this interaction is unknown. Additionally, while the native tissue environment is known to determine the properties of myogenic cells in vitro, how the aging process alters this cell memory has not been established at the molecular level. We recruited 12 young and 12 elderly women, who performed a single bout of heavy resistance exercise with the knee extensor muscles of one leg. Five days later, muscle biopsies were collected from both legs, and myogenic cells and nonmyogenic cells were isolated for in vitro experiments with mixed or separated cells and analyzed by immunostaining and RT-PCR. A lower myogenic fusion index was detected in the cells from the old versus young women, in association with differences in gene expression levels of key myogenic regulatory factors and senescence, which were further altered by performing exercise before tissue sampling. Coculture with nonmyogenic cells from the elderly led to a higher myogenic differentiation index compared with nonmyogenic cells from the young. These findings show that the in vitro phenotype and molecular profile of human skeletal muscle myoblasts and fibroblasts is determined by the age and exercise state of the original in vivo environment and help explain how exercise can enhance muscle stem cell function in old age.

Effect of Losartan on the Acute Response of Human Elderly Skeletal Muscle to Exercise

To investigate the effect of blocking the angiotensin II Type I receptor (AT1R) upon the response to acute heavy-resistance exercise in elderly human skeletal muscle. The hypothesis was that AT1R blocking would result in a superior myogenic response accompanied by down-regulation of transforming growth factor-beta and up-regulation of insulin-like growth factor-1 signaling. Twenty-eight healthy elderly men (+64 yr) were randomized into two groups, consuming either AT1R blocker (losartan, 100 mg·d) or placebo for 18 d before exercise. Participants performed one bout of heavy-unilateral-resistance exercise. Six muscle biopsies were obtained from the vastus lateralis muscles of each subject: two before exercise and four after exercise (4.5 h and 1, 4, and 7 d). Blood pressure and blood samples were collected at the same time points. Biopsies were sectioned for immunohistochemistry to determine the number of satellite cells associated with Type I and Type II fibers. Gene expression levels of Notch, connective tissue, and myogenic signaling pathways were determined by real-time reverse transcription polymerase chain reaction. Changes over time were detected for circulating creatine kinase, the number of satellite cells per Type I fiber, and most of the gene targets, with no specific effect of losartan on these. However, when compared with placebo, losartan intake resulted in a greater suppression of myostatin messenger RNA. In general, there does not seem to be any effect of AT1R blocking on satellite cell number or myogenic pathways in elderly men in the days after one bout of heavy-resistance exercise. However, the greater suppression of myostatin may prove to be beneficial over a long-term intervention designed to induce hypertrophy.

The Effects of Nitrate-Rich Supplementation on Neuromuscular Efficiency during Heavy Resistance Exercise

Objective: Nitrate-rich (NR) supplements can enhance exercise performance by improving neuromuscular function and the aerobic cost of exercise. However, little is known about the effects of nitrate on dynamic, multijoint resistance exercise.Methods: Fourteen resistance-trained men (age, 21.1 ± 0.9 years; height, 173.2 ± 2.9 cm: body mass, 77.6 ± 4.3 kg; squat one-repetition maximum [1RM], 127.5 ± 18.8 kg) participated in a randomized, double-blind, crossover experiment. Subjects consumed an NR or nitrate-poor (NP) supplement for 3 days, performed a bout of heavy resistance exercise, completed a washout, and then repeated the procedures with the remaining supplement. Before, during, and after exercise, individual and gross motor unit efficiency was assessed during isometric and dynamic muscle contractions. In addition, we compared physical performance, heart rate, lactate, and oxygen consumption (VO2).Results: Nitrate-rich supplementation resulted in lower initial muscle firing rates at rest and lower mean and maximum firing rates over the course of fatiguing exercise. Nitrate-poor supplementation was accompanied by increased mean and maximum firing rates by the end of exercise and lower initial firing rates. In addition, NR supplementation resulted in higher mean peak electromyography (EMG) amplitudes. Heart rate, lactate, and physical performance did not differ by treatment, but oxygen consumption increased more frequently when the NP supplement was consumed.Conclusion: Supplementation with an NR beetroot extract–based supplement provided neuromuscular advantages during metabolically taxing resistance exercise.

Role of Exercise and Nutrition in the Prevention of Sarcopenia

The age-associated loss of skeletal muscle mass and strength (sarcopenia) has been shown to increase the risk of injury due to falls and incidence of metabolic complications including insulin resistance and diabetes, which subsequently becomes a significant factor to disability among the elderly population. Nutrient intake is the most important anabolic stimulus for skeletal muscle. Specifically, the amino acid leucine and meal-induced insulin both independently stimulate muscle protein synthesis. However, age-specific changes in muscle anabolic responses to leucine become apparent when sub-maximal amounts of amino acids are administered in older subjects. Furthermore, insulin resistance of muscle protein metabolism with aging has been demonstrated in healthy non-diabetic older subjects. Resistance exercise is another anabolic stimulus which increases myofibrillar muscle protein synthesis in both young and older individuals. The increased muscle anabolism is apparent within 2-3 h after a single bout of heavy resistance exercise and remains elevated up to 2 d following the exercise. The mTOR signaling pathway in skeletal muscle is associated with an increased rate of muscle protein synthesis during the early recovery phase following a bout of resistance exercise. Finally, recent evidence on the cumulative effect of resistance exercise in combination with nutritional supplement on muscle protein metabolism will be discussed to propose a possible preventative measure against sarcopenia.

Effects of β-Hydroxy-β-methylbutyrate Free Acid Ingestion and Resistance Exercise on the Acute Endocrine Response.

Objective. To examine the endocrine response to a bout of heavy resistance exercise following acute β-hydroxy-β-methylbutyrate free acid (HMB-FA) ingestion. Design. Twenty resistance trained men were randomized and consumed either 1 g of HMB-FA (BetaTor) or placebo (PL) 30 min prior to performing an acute heavy resistance exercise protocol. Blood was obtained before (PRE), immediately after (IP), and 30 min after exercise (30P). Circulating concentrations of testosterone, growth hormone (GH), insulin-like growth factor (IGF-1), and insulin were assayed. Data were analyzed with a repeated measures ANOVA and area under the curve (AUC) was analyzed by the trapezoidal rule. Results. The resistance exercise protocol resulted in significant elevations from PRE in testosterone (P < 0.01), GH (P < 0.01), and insulin (P = 0.05) at IP, with GH (P < 0.01) and insulin (P < 0.01) remaining elevated at 30P. A significant interaction was noted between groups in the plasma GH response at IP, which was significantly higher following HMB-FA compared to PL (P < 0.01). AUC analysis revealed an elevated GH and IGF-1 response in the HMB-FA group compared to PL. Conclusion. HMB-FA prior to resistance exercise augments the GH response to high volume resistance exercise compared to PL. These findings provide further support for the potential anabolic benefits associated with HMB supplementation.

Acute exertion elicits a H2O2-dependent vasodilator mechanism in the microvasculature of exercise-trained but not sedentary adults.

Brachial artery flow-mediated vasodilation in exercise-trained (ET) individuals is maintained after a single bout of heavy resistance exercise compared with sedentary individuals. The purpose of this study was to determine whether vasodilation is also maintained in the microcirculation of ET individuals. A total of 51 sedentary and ET individuals underwent gluteal subcutaneous fat biopsy before and after performing a single bout of leg press exercise. Adipose arterioles were cannulated in an organ bath, and vasodilation to acetylcholine was assessed±the endothelial nitric oxide inhibitorl-NG-nitroarginine methyl ester, the cyclooxygenase inhibitor indomethacin, or the hydrogen peroxide scavenger polyethylene glycol catalase. Separate vessels (isolated from the same groups) were exposed to an intraluminal pressure of 150 mm Hg for 30 minutes to mimic the pressor response, which occurs with isometric exercise. Vasodilation to acetylcholine was reduced in microvessels from sedentary subjects after either a single weight lifting session or exposure to increased intraluminal pressure, whereas microvessels from ET individuals maintained acetylcholine-mediated vasodilation. Before weight lifting, vasodilation of microvessels from ET individuals was reduced in the presence of l-NG-nitroarginine methyl ester and indomethacin. After weight lifting or exposure to increased intraluminal pressure, polyethylene glycol catalase significantly reduced vasodilation, whereas l-NG-nitroarginine methyl ester and indomethacin had no effect. These results indicate that (1) endothelium-dependent vasodilation in the microvasculature is maintained after heavy resistance exercise in ET individuals but not in sedentary subjects and that (2) high pressure alone or during weight lifting may induce a mechanistic switch in the microvasculature to favor hydrogen peroxide as the vasoactive mediator of dilation.

Influence of training on markers of platelet activation in response to a bout of heavy resistance exercise

Recent connections between platelet activity and cardiovascular disease have raised questions of whether platelet function varies in exercising individuals. Resistance training has been linked to a possible reduction in hyper-aggregability of platelets, especially following acute strenuous exercise. The present investigation was designed to explore the effects of an acute resistance exercise test on the primary hemostatic system in both resistance-trained (RT) and untrained (UT) individuals. Ten RT (five men and five women; age, 26.0 ± 4.5 years; height, 175.12 ± 8.54 cm; weight, 79.56 ± 13.56 kg) and ten UT (five men and five women; age, 26.4 ± 6.2 years; height, 170.31 ± 7.45 cm; weight 67.88 ± 16.90 kg) individuals performed an Acute Exhaustive Resistance Exercise Test (AERET; six sets of ten repetitions of squats at 80 % of the 1-Repetition Maximum (RM)). Blood samples were obtained before, immediately after, and at 15, 60, and 120 min following the AERET. Blood samples were analyzed for platelet count, von Willebrand factor antigen (vWF:Ag), beta-thromboglobulin (β-TG), and platelet factor 4 (PF4). B-TG showed significant differences (p < 0.05) between RT and UT at +15 and +60 min. Both groups showed a main effect for time in platelet count, vWF, and β-TG following the AERET, whereas PF4 remained unchanged. All blood variables returned to baseline 120 min after exercise. Compared with UT, RT demonstrated reduced platelet activation in response to an acute bout of heavy resistance exercise. Reduced platelet activation may be attributed to training status, as shown by a reduction in plasma concentrations of B-TG in the RT group.

The Effects of Soy and Whey Protein Supplementation on Acute Hormonal Responses to Resistance Exercise in Men

Objective: For many resistance-trained men concerns exist regarding the production of estrogen with the consumption of soy protein when training for muscle strength and size. Thus, the purpose of this investigation was to examine the effects of soy and whey protein supplementation on sex hormones following an acute bout of heavy resistance exercise in resistance trained men. Methods: Ten resistance-trained men (age 21.7 ± 2.8 [SD] years; height 175.0 ± 5.4 cm; weight 84.2 ± 9.1 kg) volunteered to participate in an investigation. Utilizing a within subject randomized crossover balanced placebo design, all subjects completed 3 experimental treatment conditions supplementing with whey protein isolate (WPI), soy protein isolate (SPI), and maltodextrin placebo control for 14 days with participants ingesting 20 g of their assigned supplement each morning at approximately the same time each day. Following supplementation, subjects performed an acute heavy resistance exercise test consisting of 6 sets of 10 repetitions in the squat exercise at 80% of the subject's one repetition maximum. Results: This investigation observed lower testosterone responses following supplementation with soy protein in addition to a positive blunted cortisol response with the use of whey protein at some recovery time points. Although sex hormone binding globulin (SHBG) was proposed as a possible mechanism for understanding changes in androgen content, SHBG did not differ between experimental treatments. Importantly, there were no significant differences between groups in changes in estradiol concentrations. Conclusion: Our main findings demonstrate that 14 days of supplementation with soy protein does appear to partially blunt serum testosterone. In addition, whey influences the response of cortisol following an acute bout of resistance exercise by blunting its increase during recovery. Protein supplementation alters the physiological responses to a commonly used exercise modality with some differences due to the type of protein utilized.

Metabonomic Response to Milk Proteins after a Single Bout of Heavy Resistance Exercise Elucidated by 1H Nuclear Magnetic Resonance Spectroscopy.

In the present study, proton NMR-based metabonomics was applied on femoral arterial plasma samples collected from young male subjects (milk protein n = 12 in a crossover design; non-caloric control n = 8) at different time intervals (70, 220, 370 min) after heavy resistance training and intake of either a whey or calcium caseinate protein drink in order to elucidate the impact of the protein source on post-exercise metabolism, which is important for muscle hypertrophy. Dynamic changes in the post-exercise plasma metabolite profile consisted of fluctuations in alanine, beta-hydroxybutyrate, branched amino acids, creatine, glucose, glutamine, glutamate, histidine, lipids and tyrosine. In comparison with the intake of a non-caloric drink, the same pattern of changes in low-molecular weight plasma metabolites was found for both whey and caseinate intake. However, the study indicated that whey and caseinate protein intake had a different impact on low-density and very-low-density lipoproteins present in the blood, which may be ascribed to different effects of the two protein sources on the mobilization of lipid resources during energy deficiency. In conclusion, no difference in the effects on low-molecular weight metabolites as measured by proton NMR-based metabonomics was found between the two protein sources.

LIF is a contraction-induced myokine stimulating human myocyte proliferation

The cytokine leukemia inhibitory factor (LIF) is expressed by skeletal muscle and induces proliferation of myoblasts. We hypothesized that LIF is a contraction-induced myokine functioning in an autocrine fashion to activate gene regulation of human muscle satellite cell proliferation. Skeletal muscle LIF expression, regulation, and action were examined in two models: 1) young men performing a bout of heavy resistance exercise of the quadriceps muscle and 2) cultured primary human satellite cells. Resistance exercise induced a ninefold increase in LIF mRNA content in skeletal muscle, but LIF was not detectable in plasma of the subjects. However, electrically stimulated cultured human myotubes produced and secreted LIF, suggesting that LIF is a myokine with local effects. The well established exercise-induced signaling molecules PI3K, Akt, and mTor contributed to the regulation of LIF in cultured human myotubes as chemical inhibition of PI3K and mTor and siRNA knockdown of Akt1 were independently sufficient to downregulate LIF. Human myoblast proliferation was increased by recombinant exogenous LIF and decreased by siRNA knockdown of the endogenous LIF receptor. Finally, the transcription factors JunB and c-Myc, which promote myoblast proliferation, were induced by LIF in cultured human myotubes. Indeed, both JunB and c-Myc were also increased in skeletal muscle following resistance exercise. Our data suggest that LIF is a contraction-induced myokine, potentially acting in an autocrine or paracrine fashion to promote satellite cell proliferation.

Glucocorticoid Receptor Expression on Human B-Cells in Response to Acute Heavy Resistance Exercise

PURPOSE: In an effort to further understand the physiological role of circulating cortisol during physical stress, we examined glucocorticoid receptor (GCR) expression on B-lymphocytes in response to an acute bout of heavy resistance exercise. METHODS: Using a within subject design, resistance trained women (mean ± SD (n = 7) age: 22.13 ± 3.09 y; height: 1.69 ± 0.084 m; body mass: 65.60 ± 10.01 kg; body mass index: 22.63 ± 2.03 kg/m2) and men (mean ± SD (n = 8) age: 23.28 ± 4.26 y; height: 1.73 ± 0.086 m; body mass: 73.93 ± 12.71 kg; body mass index: 24.51 ± 2.61 kg/m2) performed an acute resistance exercise protocol (6 sets of 5 RM heavy squats) and a control test (i.e., sitting quietly under identical conditions) in a balanced, randomized order. Blood samples were obtained immediately before (pre), at the mid-point (mid), and immediately after the test (post), and at 1, 6, and 24-hrs into recovery. Glucocorticoid (GCR) receptors on circulating B lymphocytes were evaluated with flow cytometry and circulating cortisol was assayed. RESULTS: Resting GCR expression on B lymphocytes was similar between resistance trained, healthy men and women. GCR expression was elevated in anticipation of the exercise protocol (p = 0.047), decreased during the exercise protocol (p = 0.049), and increased during recovery (p = 0.05 and p = 0.03 at 1- and 6- hrs into recovery, respectively). Statistical trends for gender differences were apparent at pre, mid, and 6-hr (p = 0.039, p = 0.063, and p = 0.053, respectively). Significant gender differences in circulating cortisol responses to the exercise protocol were also observed where men had significantly higher values at mid (p = 0.002) and post (p = 0.094) compared to pre-exercise. In women however, circulating cortisol concentrations did not significantly increase in response to the squat exercise protocol. CONCLUSIONS: These findings indicate a differential relationship with circulating adrenal cortical responses to high intensity short term exercise stress but also with GCR expression. Such data provide insights into the temporal interactions between the endocrine and the immune systems in response to the physiological stress of acute heavy resistance exercise in men and women. Practical Applications: Because heavy resistance exercise training is important to sports conditioning, understanding the biological mechanism of the body's response to such training and the differences in that reaction between genders is useful in designing training protocols that would enhance athletic performance.

Testosterone Physiology in Resistance Exercise and Training

Testosterone is one of the most potent naturally secreted androgenic-anabolic hormones, and its biological effects include promotion of muscle growth. In muscle, testosterone stimulates protein synthesis (anabolic effect) and inhibits protein degradation (anti-catabolic effect); combined, these effects account for the promotion of muscle hypertrophy by testosterone. These physiological signals from testosterone are modulated through the interaction of testosterone with the intracellular androgen receptor (AR). Testosterone is important for the desired adaptations to resistance exercise and training; in fact, testosterone is considered the major promoter of muscle growth and subsequent increase in muscle strength in response to resistance training in men. The acute endocrine response to a bout of heavy resistance exercise generally includes increased secretion of various catabolic (breakdown-related) and anabolic (growth-related) hormones including testosterone. The response of testosterone and AR to resistance exercise is largely determined by upper regulatory elements including the acute exercise programme variable domains, sex and age. In general, testosterone concentration is elevated directly following heavy resistance exercise in men. Findings on the testosterone response in women are equivocal with both increases and no changes observed in response to a bout of heavy resistance exercise. Age also significantly affects circulating testosterone concentrations. Until puberty, children do not experience an acute increase in testosterone from a bout of resistance exercise; after puberty some acute increases in testosterone from resistance exercise can be found in boys but not in girls. Aging beyond 35-40 years is associated with a 1-3% decline per year in circulating testosterone concentration in men; this decline eventually results in the condition known as andropause. Similarly, aging results in a reduced acute testosterone response to resistance exercise in men. In women, circulating testosterone concentration also gradually declines until menopause, after which a drastic reduction is found. In summary, testosterone is an important modulator of muscle mass in both men and women and acute increases in testosterone can be induced by resistance exercise. In general, the variables within the acute programme variable domains must be selected such that the resistance exercise session contains high volume and metabolic demand in order to induce an acute testosterone response.

Skeletal Muscle Amino Acid Transporter mRNA Expression Is Increased In Young And Older Humans Following Resistance Exercise

INTRODUCTION: Amino acid availability is important for increasing muscle protein synthesis. However, for amino acids to be taken up and utilized by the cell, adequate transport of amino acids must occur. Interestingly, amino acid transporters have been linked to mTOR cellular signaling- a major regulator of muscle protein synthesis. PURPOSE: Therefore, we evaluated the expression levels of select amino acid transporters in young and older humans following a single bout of heavy resistance exercise. METHODS: Young (n=5) and Older (n=5) male subjects participated in a single bout of resistance exercise. Muscle biopsies were sampled at Basal, 6 and 24h post exercise. Muscle biopsies were analyzed for LAT1/SLC7A5, CD98/SLC3A2, SNAT2/SLC38A2 and PAT1/SLC36A1 mRNA expression utilizing real-time PCR. RESULTS: LAT1, CD98 and PAT1 mRNA expression were significantly elevated at 6h post in young and older subjects. However, LAT1 response was greater and was prolonged (24h) for the older subjects. Additionally, SNAT2 mRNA expression was elevated at 6 and 24h post in the older while unchanged for the younger subjects. CONCLUSIONS: These data support a rapid upregulation of amino acid transporters gene expression which may support enhanced protein synthesis following a bout of exercise. However, the robust and sustained transporter expression in the old may reflect a greater export of amino acids due to accelerated protein breakdown and muscle remodeling. Supported by ACSM Research Endowment Grant (MJD), P30 AG-024832 (MJD) and NIH/NIAMS grant R01 AR049877 (BBR)

Aging is associated with a dysregulated human skeletal muscle microRNA‐499 and ‐208b expression following resistance exercise

MicroRNAs (miRNA) are novel post‐transcriptional gene regulators associated with skeletal muscle myogenesis and tissue regeneration. Sarcopenia is associated with resistance to anabolic stimuli such as exercise and nutrition. Therefore, we hypothesized that skeletal muscle miRNA expression after exercise would be dysregulated in older humans and may play a role in the etiology of this anabolic resistance. To address our hypothesis, young (n=5) and older (n=5) male subjects participated in a single bout of leg resistance exercise and vastus lateralis muscle biopsies were sampled at Basal, 6 and 24h postexercise. Samples were analyzed utilizing real‐time PCR for gene expression levels of miR‐1, ‐206, ‐499, and ‐208b. We found that miR‐499 and ‐208b expression were upregulated at 6h postexercise in young (P&lt;0.05) but unchanged in older subjects. MiRNA‐1 and ‐206 were downregulated at 6 and 24h postexercise in both groups (P&lt;0.05). Myostatin (predicted target of miR‐499 and ‐208b) expression was decreased at 6 and 24h postexercise in both groups. IGF‐1 (predicted target of miR‐1 and ‐206) expression was elevated at 6 and 24h postexercise only in the young. We conclude that a bout of heavy resistance exercise alters the expression of human skeletal muscle miRNAs, however, aging is associated with an inability of exercise to alter miR‐499 or ‐208b. Identifying gene targets of these miRNAs will be the focus of future work.Supported by NIA P30 AG‐024832 (MJD) &amp; NIAMS grant R01 AR049877 (BBR)

Rapamycin prevents the post‐exercise increase in protein synthesis and alters cell signaling in human skeletal muscle

Resistance exercise stimulates mTOR signaling and muscle protein synthesis (MPS) during post‐exercise recovery in humans. Rapamycin is a specific inhibitor of mTOR and is often used to inhibit protein synthesis in cell models and rodent skeletal muscle in vivo. We hypothesized that the administration of rapamycin to human subjects prior to a bout of resistance exercise would prevent the increase in MPS during early post‐exercise recovery. We studied young men that ingested rapamycin (12mg) 2 hr prior to exercise (Rapamycin; N=7) and a Control group that did not receive rapamycin (N=8). Rapamycin and Control subjects performed a bout of heavy resistance exercise and muscle biopsies were obtained at 1 and 2 hours post‐exercise. Stable isotope and immunoblotting techniques were used to determine MPS and phosphorylation of proteins involved in the regulation of MPS. We found that MPS increased during post‐exercise recovery in the Control group (P&lt;0.05) but was unchanged in the Rapamycin group (P&gt;0.05). In addition, phosphorylation of mTOR (Ser2448), S6K1 (Thr389) and S6 (Ser240/244 and 235/236) were partially inhibited and S6K1 (Thr421/Ser424), eEF2 (Thr56) and ERK1/2 (Thr202/Tyr204) and MNK1 (Thr197/202) were completely blocked during post‐exercise recovery in the Rapamycin group. Raptor association with mTORC1 also tended to be higher in the Control group (as compared to the Rapamycin group) at 2 hours post‐exercise (P=0.06). We conclude that the increase in MPS following an acute bout of resistance exercise appears to be rapamycin dependent indicating that mTOR signaling is playing an important role in regulating the post‐exercise protein anabolic response.Supported by NIH/NIAMS grant # RO1 AR049877 and P30AG024832.

Expression of growth-related genes in young and older human skeletal muscle following an acute stimulation of protein synthesis

Muscle growth is associated with an activation of the mTOR signaling pathway and satellite cell regulators. The purpose of this study was to determine whether 17 selected genes associated with mTOR/muscle protein synthesis and the satellite cells/myogenic program are differentially expressed in young and older human skeletal muscle at rest and in response to a potent anabolic stimulus [resistance exercise + essential amino acid ingestion (RE+EAA)]. Twelve male subjects (6 young, 6 old) completed a bout of heavy resistance exercise. Muscle biopsies were obtained before and at 3 and 6 h post RE+EAA. Subjects ingested leucine-enriched essential amino acids at 1 h postexercise. mRNA expression was determined using qRT-PCR. At rest, hVps34 mRNA was elevated in the older subjects (P < 0.05) while there was a tendency for levels of myoD, myogenin, and TSC2 mRNA to be higher than young. The anabolic stimulus (RE+EAA) altered mRNAs associated with mTOR regulation. Notably, REDD2 decreased in both age groups (P < 0.05) but the expression of Rheb mRNA increased only in the young. Finally, cMyc mRNA was elevated (P < 0.05) in both young and old at 6 h post RE+EAA. Furthermore, RE+EAA also increased expression of several mRNAs associated with satellite function in the young (P < 0.05), while expression of these mRNAs did not change in the old. We conclude that several anabolic genes in muscle are more responsive in young men post RE+EAA. Our data provide new insights into the regulation of genes important for transcription and translation in young and old human skeletal muscle post RE+EAA.

A Biomechanical Analysis of the Acute Effects of Complex Training Using Lower Limb Exercises

The aim of this study was to investigate the current practice of complex training using a lower body combination of exercises. It was hypothesized that a bout of heavy resistance exercise (HRE), as typically used in complex training, would lead to enhanced performance (in the form of counter-movement [CMJ] and drop [DJ] jump height) and increased electromyographical (EMG) activity in subsequent plyometric exercise, also typical of complex training. Eight strength trained men performed 2 conditions: HRE or control (no-HRE) in a counter-balanced order. Both conditions involved 4 sets of 6-jump trials (3-CMJ/ 3-DJ). The first set of jumps was used as a baseline. For the HRE condition, 5-squats at 85% of 1 repetition maximum (1RM) followed shortly after the first set, while the second, third and fourth sets followed at 3-, 10-, and 20-minutes post-HRE, respectively. The control condition involved the same procedure, but no exercise separated the first 2-sets. There were no significant main effects (p > 0.05) for any CMJ performance variable or EMG activity regardless of muscle or phase of jump. There were no significant (p > 0.05) main effects of heavy resistance exercise on DJ performance variables. Only the biceps femoris during the propulsive phase of the DJ was significantly higher (p < 0.05) following HRE compared to no-HRE. Some trends in the data were evident and the power of the statistical tests was low. It was concluded that no evidence was found to support the experimental hypothesis although the absence of a treatment effect could not be ruled out. From a practical point of view, undertaking a bout of HRE had no adverse effects on subsequent plyometric performance and so some of the advantages of complex training still remain.

Lymphocyte proliferation in response to acute heavy resistance exercise in women: influence of muscle strength and total work.

Little is understood about the immune responses to heavy resistance exercise. The purpose of this investigation was to determine the influence of physical strength and the ability to do more total work on lymphocyte proliferation after an acute bout of heavy resistance exercise. A group of 50 healthy but nonstrength trained women were recruited for the study and tested for their one repetition maximum (i.e. 1 RM or maximal mass lifted once). From the normal distribution of strength the top and bottom 8 women [mean age 22.5 (SD 3.1) years] were asked to volunteer to define our two groups (i.e. high strength and low strength). The two groups were significantly different (P < 0.05) in 1 RM squat strength [low strength 39.9 (SD 4.6) kg, 0.65 (SD 0.08) kg.kg body mass-1 and high strength 72.2 (SD 10.7) kg, 1.1 (SD 0.12) kg.kg body mass-1] but were not significantly different in body mass, age, activity levels, and menstrual status (all in same phase). Each performed a resistance exercise protocol consisting of six sets of 10 RM squats with 2 min rest between the sets. The 10 RM loads and total work were significantly greater in the high strength group than in the low strength group. Blood samples were obtained pre-exercise and immediately post-exercise for test for lactate (significant increase with exercise) and cortisol (no changes) concentrations with no differences noted between groups. Immunological assays on the blood samples determined the incorporation of tritiated thymidine by lymphocytes in responses to concanavalin A (ConA), phytohemagglutinin (PHA), and pokeweed mitogen (PWM). Following the squat exercise, there was a significant decrease in lymphocyte responsiveness to PWM in the high strength but not in the low strength group for both total proliferation and proliferation adjusted per B or T cell. On the other hand, lymphocytes from the low strength group proliferated to a significantly greater extent (adjusted per T cell) in response to ConA and PHA. These data indicate that the heavy resistance exercise protocol reduced the lymphocyte proliferative responses only in the stronger group of subjects. This effect may have been due to the high absolute total work and the greater exercise stress created by the resistance exercise protocol in the high strength group. Therefore, individuals performing at the same relative exercise intensity (i.e. 10 RM) in a resistance exercise protocol may have different immune responses stemming from differences in absolute total work performance.

Changes in human muscle protein synthesis after resistance exercise.

The purpose of this study was to investigate the magnitude and time course for changes in muscle protein synthesis (MPS) after a single bout of resistance exercise. Two groups of six male subjects performed heavy resistance exercise with the elbow flexors of one arm while the opposite arm served as a control. MPS from exercised (ex) and control (con) biceps brachii was assessed 4 (group A) and 24 h (group B) postexercise by the increment in L-[1-13C]leucine incorporation into muscle biopsy samples. In addition, RNA capacity and RNA activity were determined to assess whether transcriptional and/or translational processes affected MPS. MPS was significantly elevated in biceps of the ex compared with the con arms of both groups (group A, ex 0.1007 +/- 0.0330 vs. con 0.067 +/- 0.0204%/h; group B ex 0.0944 +/- 0.0363 vs. con 0.0452 +/- 0.0126%/h). RNA capacity was unchanged in the ex biceps of both groups relative to the con biceps, whereas RNA activity was significantly elevated in the ex biceps of both groups (group A, ex 0.19 +/- 0.10 vs. con 0.12 +/- 0.05 micrograms protein.h-1.microgram-1 total RNA; group B, ex 0.18 +/- 0.06 vs. con 0.08 +/- 0.02 micrograms protein.h-1.microgram-1 total RNA). The results indicate that a single bout of heavy resistance exercise can increase biceps MPS for up to 24 h postexercise. In addition, these increases appear to be due to changes in posttranscriptional events.