Resistance Training-induced Changes Research Articles

Resistance training-induced changes in muscle proteolysis and extracellular matrix remodeling biomarkers in the untrained and trained states.

Resistance training (RT) induces muscle growth at varying rates across RT phases, and evidence suggests that the muscle-molecular responses to training bouts become refined or attenuated in the trained state. This study examined how proteolysis-related biomarkers and extracellular matrix (ECM) remodeling factors respond to a bout of RT in the untrained (UT) and trained (T) state. Participants (19 women and 19 men) underwent 10weeks of RT. Biopsies of vastus lateralis were collected before and after (24h) the first (UT) and last (T) sessions. Vastus lateralis cross-sectional area (CSA) was assessed before and after the experimental period. There were increases in muscle and type II fiber CSAs. In both the UT and T states, calpain activity was upregulated and calpain-1/-2 protein expression was downregulated from Pre to 24h. Calpain-2 was higher in the T state. Proteasome activity and 20S proteasome protein expression were upregulated from Pre to 24h in both the UT and T. However, proteasome activity levels were lower in the T state. The expression of poly-ubiquitinated proteins was unchanged. MMP activity was downregulated, and MMP-9 protein expression was elevated from Pre to 24h in UT and T. Although MMP-14 protein expression was acutely unchanged, this marker was lower in T state. TIMP-1 protein levels were reduced Pre to 24h in UT and T, while TIMP-2 protein levels were unchanged. Our results are the first to show that RT does not attenuate the acute-induced response of proteolysis and ECM remodeling-related biomarkers.

P23-012-23 Effect of Dietary Protein Quantity and Source on Resistance Training-Induced Changes in Skeletal Muscle Strength, Size, and Quality in Older Women

P23-012-23 Effect of Dietary Protein Quantity and Source on Resistance Training-Induced Changes in Skeletal Muscle Strength, Size, and Quality in Older Women

Resistance training-induced improvement in physical function is not associated to changes in endocrine somatotropic activity in prefrail older adults

ContextResistance training improves muscle function in prefrail and frail elderly. The role of the somatotropic axis in this physiologic process remains unclear. Insulin-like growth factor I (IGF-I) and its associated proteins Insulin-like growth factor binding protein 3 (IGFBP3) and acid labile subunit (ALS) build a circulating ternary complex that mediates growth hormone (GH) effects on peripheral organs and can serve as a measure of endocrine somatotropic activity. ObjectiveThe aim of this study was to assess the association between resistance training-induced changes in physical performance and basal levels of IGF-I, IGFBP-3 and ALS in prefrail older adults. Methods69 prefrail community-dwelling older adults, aged 65 to 94 years, were randomly assigned to a 12-week period of strength or power training or to a control group. The study was registered at clinicaltrials.gov as NCT00783159. Serum concentrations of IGF-I, IGFBP-3 and ALS were measured at rest before and after the intervention. Hormonal differences were examined in relation to changes in physical performance assessed by the Short Physical Performance Battery (SPPB). ResultsWhile resistance training led to significant improvements in SPPB score it did not induce significant differences in somatotropic hormone concentrations. Pre- and post-intervention changes in IGF-I, IGFBP-3, ALS or IGF/IGFBP-3 molar ratio were not related to the intervention mode, even after adjustment for age, sex, nutritional status, as well as SPPB and hormone concentrations at baseline. ConclusionTraining-induced improvements in physical performance in prefrail older adults were not associated with significant changes in endocrine somatotropic activity.

The Effect of Whole-Body Traditional and Functional Resistance Training on CAVI and Its Association With Muscular Fitness in Untrained Young Men.

Background: Resistance training-induced changes in the muscle function is essential for the health promotion of the young and older, but the discrepancies of the effect of resistance training on arterial stiffness leads to the divergence regarding to the effect of resistance training on cardiovascular health. What confuses our understanding in this field may be the following factors: external load (higher intensity vs. lighter intensity), participants’ cardiovascular health, and arterial stiffness assessment measurement. The purpose of the present study was to investigate the effects of the whole-body traditional high-intensity vs. functional low-intensity resistance training protocol on systemic arterial stiffness, and their association with muscular fitness components in untrained young men. Methods: In this randomized controlled trial, twenty-nine untrained young men (mean age about 22.5 years old) were randomized into a 6-weeks (three sessions per week) supervised whole-body traditional high-intensity resistance group (TRT, n = 15) consisting of 4–5 sets of 12 repetitions (70%1RM, lower-repetitions) or a whole-body functional low-intensity resistance group (FRT, n = 14) with 4–5 sets of 20 repetitions (40%1RM, higher-repetitions) to volitional failure. The systemic arterial stiffness (cardio-ankle vascular index, CAVI) and muscular fitness components were assessed before and after the 6-weeks training program. Results: There was a significant decrease (pre-post) for CAVI only in FRT group (p < 0.05), but no significant difference was observed between two groups. In addition, the TRT and FRT groups showed equally significantly increased in maximal strength, muscular endurance and power (within group: both p < 0.01); however, the independent t test exhibited that the difference between two groups in terms of change in maximal strength, muscular endurance and power were no significant (p > 0.05). Furthermore, the reduction in CAVI was negatively correlated with the increase in 1RM of bench press for all participants (r = −0.490, p < 0.01). Conclusion:Using present criterion-standard assessments measurements demonstrates that CAVI was significantly reduced after 6-weeks functional resistance training with beneficial effect on muscular fitness. Negative and significant association between CAVI and 1RM bench press indicated the cardiovascular health may be involved in the regulation of resistance training.

Stretch-Shortening Cycle Potentiation and Resistance Training-Induced Changes in Walking Economy/Ease and Activity-Related Energy Expenditure in Older Women.

Hunter, GR, Singh, H, Martins, C, Baranauskas, MN, and Carter, SJ. Stretch-shortening cycle potentiation and resistance training-induced changes in walking economy/ease and activity-related energy expenditure in older women. J Strength Cond Res 35(5): 1345-1349, 2021-Use of elastic energy to improve economy and ease of walking may be important for older adults. The purpose of this investigation was to determine whether baseline (i.e., untrained) stretch-shortening cycle potentiation (SSCP) was associated with potential changes in free-living activity-related energy expenditure (AEE) after supervised exercise training. Sedentary, postmenopausal women (n = 64) between 60 and 74 years of age were evaluated before and after 16 weeks of combined aerobic and resistance training. Assessments included: (a) body composition (dual-energy X-ray absorptiometry), (b) resting energy expenditure (indirect calorimetry), (c) submaximal and maximal walking (treadmill/indirect calorimetry), (d) total energy expenditure (doubly labeled water), and (e) one repetition maximum performed on an incline leg press and SSCP (calculated as the difference between concentric and countermovement leg press throw). Results indicated that baseline SSCP was related (r = -0.29; p < 0.02) to changes in AEE. However, subjects who possessed a high baseline SSCP did not increase SSCP or AEE, whereas subjects with low to moderate baseline SSCP demonstrated a significant increase in both SSCP (low +0.54 and moderate +0.47 m·s-1) and AEE (low +158 and moderate +333 kcal·d-1) post-training (all p less than 0.05). Our findings suggest that among subjects with low to moderate baseline SSCP, 16 weeks of combined aerobic and resistance training can increase SSCP and free-living AEE. However, subjects with high baseline SSCP may require tailored exercise to increase SSCP and possibly AEE.

Does Muscle Hypertrophy Relate To Resistance Training-Induced Changes In Myofibrillar Protein Synthesis In Women?

Resistance exercise (RE) elevates skeletal muscle myofibrillar protein synthesis (MyoPS) for up to 48h, which can be measured under ‘free-living’ conditions using deuterium oxide (D2O). The accumulation of repeated bouts of RE (resistance training—RT) results in skeletal muscle hypertrophy, which in men has been reported to correlate with post-RE ‘free-living’ MyoPS only in the trained state. However, the impact of training status on acute responses to RE and their relationship to hypertrophic adaptations has yet to be investigated in women. PURPOSE: The present study examined the MyoPS response over 48h of recovery from an acute bout of RE in the untrained (UT) and trained (T) state to determine its association with hypertrophic adaptations in women. METHODS: Ten recreationally active young women (23±5 yr, 62.3±12.0 kg, 23.7±7.4 % body fat; mean±SD) underwent ~8 wk of supervised whole-body RT (4 x 10 repetitions, 75% 1 repetition maximum (1RM), 3x/wk). Whole-body fat free mass (FFM; BODPOD), vastus lateralis muscle thickness (MT; B-mode ultrasound) and 1RM for each completed exercise were measured in the UT and T state to quantify training responses. MyoPS was measured during the mid-follicular phase (day 3-9 of the menstrual cycle) at rest pre-training and for 48h following the first and final bout of RE using orally administered D2O. Muscle biopsies were obtained at pre-RE (0h), 24h and 48h post-RE to determine MyoPS in both the UT and T state. RESULTS: Following RT, there was a ~3.4% increase in FFM (49.3±6.4 vs. 51.0±6.9 kg; P < 0.001) and ~8.8% increase in MT (2.31±0.39 vs. 2.50±0.38 cm; P < 0.05). Representative 1RM strength increased for bench press and leg press exercise (28.5±5.8 kg vs. 38.7±9.8 kg and 151.6±63.5 vs. 259.3±92.7 kg, respectively; P < 0.01). Forthcoming analysis will determine if: i) training alters the post-exercise MyoPS response, and; ii) whether muscle hypertrophy correlates with acute MyoPS in the UT and/or T state. CONCLUSIONS: Women responded favourably to ~8 wk of RT with significant gains in FFM, MT and 1RM strength. Ongoing analysis will provide insight into the potential relationship between acute muscle protein synthesis and training-induced hypertrophy in the understudied female population. Supported by the Natural Sciences and Engineering Research Council of Canada.

Physical resistance training-induced changes in lipids metabolism pathways and apoptosis in prostate

BackgroundAltered lipid metabolism is an important characteristic of neoplastic cells, with androgens and growth factors being major regulatory agents of the lipid metabolism process. We investigated the effect of physical resistance training on lipid metabolism and apoptosis in the adult Wistar rat prostate.MethodsTwo experimental groups represented sedentary and physical resistance training. Three days per week for 13 weeks, rats performed jumps in water carrying a weight load strapped to their chests as part of a physical resistance exercise protocol. Two days after the last training session, rats were anesthetized and sacrificed for blood and prostate analysis.ResultsPhysical exercise improved feeding efficiency, decreased weight gain, regulated the serum-lipid profile, and modulated insulin-like growth factor-1 (IGF-1) and free testosterone concentration. Furthermore, upregulation of cluster of differentiation 36 (CD36), sterol regulatory element binding protein-1 (SREBP-1), sterol regulatory element-binding protein cleavage-activating protein (SCAP), and reduced lysosome membrane protein (LIMPII) expression were also observed in the blood and prostates of trained rats. Consistent with these results, caspase-3 expression was upregulating and the BCL-2/Bax index ratio was decreased in trained rats relative to sedentary animals.ConclusionsIn this work, physical resistance training can alter lipid metabolism and increase markers of apoptosis in the prostate, suggesting physical resistance training as a potential novel therapeutic strategy for treating prostate cancer.

Leucine Metabolites Do Not Enhance Training-induced Performance or Muscle Thickness.

We aimed to conduct a double-blind randomized controlled pragmatic trial to evaluate the effects of off-the-shelf leucine metabolite supplements of α-HICA, HMB-FA, and HMB-Ca on resistance training-induced changes in muscle thickness and performance. Forty men were randomly assigned to receive α-HICA (n = 10, fat-free mass [FFM] = 62.0 ± 7.1 kg), HMB-FA (n = 11, FFM = 62.7 ± 10.5 kg), HMB-Ca (n = 9, FFM = 65.6 ± 10.1 kg), or placebo (PLA; n = 10, FFM = 64.2 ± 5.7 kg). The training program consisted of whole body thrice weekly resistance training for 8 wk (seven exercises per session, three to four sets per session, at 70%-80% one repetition maximum). Skeletal muscle thickness by ultrasound, performance measures, and blood measures (creatine kinase, insulin-like growth factor 1, growth hormone, cortisol, and total testosterone) were evaluated at baseline and at the end of weeks 4 and 8. Time-dependent changes were observed for muscle thickness (P < 0.001), one repetition maximum bench press and squat (P < 0.001), Wingate peak power (P = 0.02), countermovement jump height (P = 0.03), power (P = 0.006), creatine kinase, insulin-like growth factor-1, growth hormone, and cortisol (all P < 0.001). No significant between-group or time-group interactions were observed. No leucine metabolite resulted in any ergogenic effects on any outcome variable. Supplementation with leucine metabolites-α-HICA, HMB-FA, or HMB-Ca-is not a supplementation strategy that improves muscle growth and strength development in young adult men.

The impact of malnutrition on efficacy of resistance training in community-dwelling older adults.

Few studies have focused on the effect of resistance training under conditions of malnutrition in older adults requiring long-term care. The purpose of this study was to investigate the influence of nutritional status in older adults on resistance training-induced changes in physical performance. A total of 91 community-dwelling older adults participated in 24weeks of resistance training. Participants used the 60% of one repetition maximum for three sets of 10 repetitions for resistance training. Short Physical Performance Battery (SPPB), Mini Nutritional Assessment Short Form (MNA-SF), Barthel Index, and grip strength were measured before and after the resistance training. The participants were classified into three groups according to the MNA-SF score at baseline (0 to 7 as malnutrition group, 8 to 11 as at risk group, and 12 to 14 as well-nourished group). In comparing the preintervention and postintervention changes in functional fitness of the groups, there was a significant Group×Time interaction for SPPB scores (F=11.59, p<0.01), 4-m walk speed (F=5.87, p<0.01), and grip strength (F=3.27, p<0.05). Multivariate logistic regression analysis showed that well-nourished group was significantly more likely to improvement of physical function (odds ratio 3.08, 95% confidence interval [1.54, 6.15], p<0.01). The results of study revealed that malnutrition was an independent negative factor of effects of resistance training in older adults. These results suggested that effects of resistance training may be affected by the nutritional state.

Effects of protein supplements consumed with meals, versus between meals, on resistance training-induced body composition changes in adults: a systematic review.

The impact of timing the consumption of protein supplements in relation to meals on resistance training-induced changes in body composition has not been evaluated systematically. The aim of this systematic review was to assess the effect of consuming protein supplements with meals, vs between meals, on resistance training-induced body composition changes in adults. Studies published up to 2017 were identified with the PubMed, Scopus, Cochrane, and CINAHL databases. Two researchers independently screened 2077 abstracts for eligible randomized controlled trials of parallel design that prescribed a protein supplement and measured changes in body composition for a period of 6 weeks or more. In total, 34 randomized controlled trials with 59 intervention groups were included and qualitatively assessed. Of the intervention groups designated as consuming protein supplements with meals (n = 16) vs between meals (n = 43), 56% vs 72% showed an increase in body mass, 94% vs 90% showed an increase in lean mass, 87% vs 59% showed a reduction in fat mass, and 100% vs 84% showed an increase in the ratio of lean mass to fat mass over time, respectively. Concurrently with resistance training, consuming protein supplements with meals, rather than between meals, may more effectively promote weight control and reduce fat mass without influencing improvements in lean mass.

Resistance training prevents muscle fibrosis and atrophy via down-regulation of C1q-induced Wnt signaling in senescent mice.

Increased complement component 1q (C1q) secretion with aging leads to muscle fibrosis and atrophy whereas resistance training attenuates circulating C1q levels. This study aimed to clarify whether resistance exercise-induced reduction of C1q secretion contributes to the inhibition of fibrosis and atrophy in aged muscles. Young (13-wk-old) and aged (38-wk-old) senescence-accelerated mouse prone 1 mice were randomly assigned to one of 4 groups: a young or aged sedentary control group, or a young or aged resistance training (climbing a ladder 3 d/wk for 12 wk) group. We found that resistance training ameliorated muscle fibrosis and atrophy in aged mice, concomitant with decreased circulating and muscle C1q levels and attenuated activation of muscle Wnt signaling (glycogen synthase kinase β/β-catenin), including β-catenin in satellite (Pax7+/DAPI+) and fibroblast (vimentin+/DAPI+) cells. Furthermore, during muscle regeneration after mice were injured by cardiotoxin injection, we observed a reduction in circulating C1q levels, the inhibition of muscle fibrosis and repair, and decreased in the activation of muscle cytoplasmic and nuclear β-catenin in aged mice from the resistance training group, but these effects were cancelled by a single preadministration of exogenous recombinant C1q. In addition, resistance training attenuated aging-related muscle loss concomitant with decreased expression of both muscle ring-finger protein 1 and muscle atrophy F-box in the muscle. Thus, resistance training-induced changes in circulating C1q levels may contribute to the prevention of muscle fibrosis and atrophy via muscle Wnt signaling in senescent mice.-Horii, N., Uchida, M., Hasegawa, N., Fujie, S., Oyanagi, E., Yano, H., Hashimoto, T., Iemitsu, M. Resistance training prevents muscle fibrosis and atrophy via down-regulation of C1q-induced Wnt signaling in senescent mice.

The Effects of Krill Oil on mTOR Signaling and Resistance Exercise: A Pilot Study.

Introduction Krill oil supplementation has been shown to improve postexercise immune function; however, its effect on muscle hypertrophy is currently unknown. Therefore, the aim of present study was to investigate the ability of krill oil to stimulate mTOR signaling and its ability to augment resistance training-induced changes in body composition and performance. Methods C2C12 myoblasts cells were stimulated with krill oil or soy-derived phosphatidylcholine (S-PC), and then, the ratio of P-p70-389 to total p70 was used as readout for mTOR signaling. In double-blind, placebo-controlled study, resistance trained subjects consumed either 3 g krill oil daily or placebo, and each took part in an 8-week periodized resistance training program. Body composition, maximal strength, peak power, and rate of perceived recovery were assessed collectively at the end of weeks 0 and 8. In addition, safety parameters (comprehensive metabolic panel (CMP), complete blood count (CBC), and urine analysis (UA)) and cognitive performance were measured pre- and posttesting. Results Krill oil significantly stimulated mTOR signaling in comparison to S-PC and control. No differences for markers on the CMP, CBC, or UA were observed. Krill oil significantly increased lean body mass from baseline (p=0.021, 1.4 kg, +2.1%); however, there were no statistically significant differences between groups for any measures taken. Conclusion Krill oil activates mTOR signaling. Krill oil supplementation in athletes is safe, and its effect on resistance exercise deserves further research.

A review of resistance training-induced changes in skeletal muscle protein synthesis and their contribution to hypertrophy.

Muscle protein synthesis (MPS) is stimulated by resistance exercise (RE) and is further stimulated by protein ingestion. The summation of periods of RE-induced increases in MPS can induce hypertrophy chronically. As such, studying the response of MPS with resistance training (RT) is informative, as adaptations in this process can modulate muscle mass gain. Previous studies have shown that the amplitude and duration of increases in MPS after an acute bout of RE are modulated by an individual's training status. Nevertheless, it has been shown that the initial responses of MPS to RE and nutrition are not correlated with subsequent hypertrophy. Thus, early acute responses of MPS in the hours after RE, in an untrained state, do not capture how MPS can affect RE-induced muscle hypertrophy. The purpose of this review is provide an in-depth understanding of the dynamic process of muscle hypertrophy throughout RT by examining all of the available data on MPS after RE and in different phases of an RT programme. Analysis of the time course and the overall response of MPS is critical to determine the potential protein accretion after an RE bout. Exercise-induced increases in MPS are shorter lived and peak earlier in the trained state than in the untrained state, resulting in a smaller overall muscle protein synthetic response in the trained state. Thus, RT induces a dampening of the MPS response, potentially limiting protein accretion, but when this occurs remains unknown.

Serum C1q as a novel biomarker of sarcopenia in older adults.

Aging-induced elevation in C1q secretion activates the Wnt signaling pathway in muscles, leading to the development of muscle fibrosis. However, the association between serum C1q level and muscle mass and strength remains unclear in humans. The aim of the study was to elucidate whether serum C1q level is associated with aging- and resistance training-induced changes in muscle mass and strength. First, in a cross-sectional study, we investigated the association between serum C1q level and muscle mass and strength in 131 healthy subjects, aged 20-81 yr. Second, in an intervention study, we examined the association between the effects of serum C1q level and muscle mass and strength on 12 wk resistance training in 11 healthy older adults (60-81 yr). In the cross-sectional study, serum C1q level increased with aging and was negatively correlated with muscle mass and strength. Furthermore, 12 wk resistance training in older adults reduced the age-associated elevation in serum C1q levels. The training effect of serum C1q level significantly correlated with the change in the cross-sectional area of the thigh (r = -0.703; P < 0.01). Serum C1q level may reflect loss of muscle mass; therefore, C1q may be a novel biomarker of sarcopenia.

Phosphatidic acid enhances mTOR signaling and resistance exercise induced hypertrophy.

IntroductionThe lipid messenger phosphatidic acid (PA) plays a critical role in the stimulation of mTOR signaling. However, the mechanism by which PA stimulates mTOR is currently unknown. Therefore, the purpose of this study was to compare the effects of various PA precursors and phospholipids on their ability to stimulate mTOR signaling and its ability to augment resistance training-induced changes in body composition and performance.MethodsIn phase one, C2C12 myoblasts cells were stimulated with different phospholipids and phospholipid precursors derived from soy and egg sources. The ratio of phosphorylated p70 (P-p70-389) to total p70 was then used as readout for mTOR signaling. In phase two, resistance trained subjects (n = 28, 21 ± 3 years, 77 ± 4 kg, 176 ± 9 cm) consumed either 750 mg PA daily or placebo and each took part in an 8 week periodized resistance training program.ResultsIn phase one, soy-phosphatidylserine, soy-Lyso-PA, egg-PA, and soy-PA stimulated mTOR signaling, and the effects of soy-PA (+636%) were significantly greater than egg-PA (+221%). In phase two, PA significantly increased lean body mass (+2.4 kg), cross sectional area (+1.0 cm), and leg press strength (+51.9 kg) over placebo.ConclusionPA significantly activates mTOR and significantly improved responses in skeletal muscle hypertrophy, lean body mass, and maximal strength to resistance exercise.

Inhomogeneous architectural changes of the quadriceps femoris induced by resistance training

This study aimed to clarify whether resistance training-induced changes in muscle architecture are homogeneous among the quadriceps and over different regions within each muscle. Eleven recreationally active men (27 ± 2 years) completed a 12-week resistance training program for knee extensors. Before and after the intervention, muscle thicknesses, fascicle lengths, and pennation angles of the four muscles (vastus lateralis, vastus medialis, vastus intermedius, rectus femoris) in several regions (2-4 regions per each muscle) were measured using ultrasonography. Anatomical cross-sectional areas (ACSAs) at the same positions as the ultrasound measurements were determined from magnetic resonance images. Relative increases in the ACSA, muscle thickness, and pennation angle of the rectus femoris were significantly greater than those of the vasti. Relative increases in the ACSAs of the vastus lateralis and rectus femoris were significantly greater in the distal than in the proximal region, and those in the muscle thickness and pennation angle of the vastus intermedius were significantly greater in the medial than in the lateral region. Fascicle lengths did not change in any muscles. The interrelations between muscle thickness and pennation angle remained unchanged after the intervention, with a significant association between the relative changes of the two variables. The current results indicate that (1) hypertrophy of the quadriceps femoris is associated with a proportional increase in pennation angle but not necessarily in fascicle length, and (2) training-induced changes in muscle size and pennation do not evenly occur among the quadriceps, along or across a muscle.

Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training

The purpose of this study was to investigate associations between acute exercise-induced hormone responses and adaptations to high intensity resistance training in a large cohort (n = 56) of young men. Acute post-exercise serum growth hormone (GH), free testosterone (fT), insulin-like growth factor (IGF-1) and cortisol responses were determined following an acute intense leg resistance exercise routine at the midpoint of a 12-week resistance exercise training study. Acute hormonal responses were correlated with gains in lean body mass (LBM), muscle fibre cross-sectional area (CSA) and leg press strength. There were no significant correlations between the exercise-induced elevations (area under the curve—AUC) of GH, fT and IGF-1 and gains in LBM or leg press strength. Significant correlations were found for cortisol, usually assumed to be a hormone indicative of catabolic drive, AUC with change in LBM (r = 0.29, P < 0.05) and type II fibre CSA (r = 0.35, P < 0.01) as well as GH AUC and gain in fibre area (type I: r = 0.36, P = 0.006; type II: r = 0.28, P = 0.04, but not lean mass). No correlations with strength were observed. We report that the acute exercise-induced systemic hormonal responses of cortisol and GH are weakly correlated with resistance training-induced changes in fibre CSA and LBM (cortisol only), but not with changes in strength.Electronic supplementary materialThe online version of this article (doi:10.1007/s00421-011-2246-z) contains supplementary material, which is available to authorized users.

Comparative effects of resistance training on peak isometric torque, muscle hypertrophy, voluntary activation and surface EMG between young and elderly women

We compared the effect of a 10-week resistance training program on peak isometric torque, muscle hypertrophy, voluntary activation and electromyogram signal amplitude (EMG) of the knee extensors between young and elderly women. Nine young women (YW; range 20-30 years) and eight elderly women (EW; 64-78 years) performed three sets of ten repetitions at 75% 1 repetition maximum for the bilateral leg extension and bilateral leg curl 3 days per week for 10 weeks. Peak isometric torque, EMG and voluntary activation were assessed before, during, and after the training period, while knee extensor lean muscle cross-sectional area (LCSA) and lean muscle volume (LMV) were assessed before and after the training period only. Similar increases in peak isometric torque (16% and 18%), LCSA (13% and 12%), LMV (10% and 9%) and EMG (19% and 21%) were observed between YW and EW, respectively, at the completion of training (P<0.05), while the increase in voluntary activation in YW (1.9%) and EW (2.1%) was not significant (P>0.05). These findings provide evidence to indicate that participation in regular resistance exercise can have significant neuromuscular benefits in women independent of age. The lack of change in voluntary activation following resistance training in both age groups despite the increase in EMG may be related to differences between measurements in their ability to detect resistance training-induced changes in motor unit activity. However, it is possible that neural adaptation did not occur and that the increase in EMG was due to peripheral adaptations.