Acute changes in serum and skeletal muscle steroids in resistance-trained men

IntroductionResistance exercise can significantly increase serum steroid concentrations after an exercise bout. Steroid hormones are involved in the regulation of several important bodily functions (e.g., muscle growth) through both systemic delivery and local production. Thus, we aimed to determine whether resistance exercise-induced increases in serum steroid hormone concentrations are accompanied by enhanced skeletal muscle steroid concentrations, or whether muscle contractions per se induced by resistance exercise can increase intramuscular steroid concentrations.MethodsA counterbalanced, within-subject, crossover design was applied. Six resistance-trained men (26 ± 5 years; 79 ± 8 kg; 179 ± 10 cm) performed a single-arm lateral raise exercise (10 sets of 8 to 12 RM - 3 min rest between sets) targeting the deltoid muscle followed by either squat exercise (10 sets of 8 to 12 RM - 1 min rest) to induce a hormonal response (high hormone [HH] condition) or rest (low hormone [LH] condition). Blood samples were obtained pre-exercise and 15 min and 30 min post-exercise; muscle specimens were harvested pre-exercise and 45 min post-exercise. Immunoassays were used to measure serum and muscle steroids (total and free testosterone, dehydroepiandrosterone sulfate, dihydrotestosterone, and cortisol; free testosterone measured only in serum and dehydroepiandrosterone only in muscle) at these time points.ResultsIn the serum, only cortisol significantly increased after the HH protocol. There were no significant changes in muscle steroid concentrations after the protocols.DiscussionOur study provides evidence that serum steroid concentration increases (cortisol only) seem not to be aligned with muscle steroid concentrations. The lack of change in muscle steroid after protocols suggests that resistance-trained individuals were desensitized to the exercise stimuli. It is also possible that the single postexercise timepoint investigated in this study might be too early or too late to observe changes. Thus, additional timepoints should be examined to determine if RE can indeed change muscle steroid concentrations either by skeletal muscle uptake of these hormones or the intramuscular steroidogenesis process

Muscle fiber hypertrophy and myonuclei addition: a systematic review and meta-analysis

Introduction The myonuclear domain theory postulates that myonuclei are added to muscle fibers when increases in fiber cross-sectional area (i.e., hypertrophy) are ≥26%. However, recent studies have reported increased myonuclear content with lower levels (e.g., 12%) of muscle fiber hypertrophy. Purpose This study aimed to determine whether a muscle fiber hypertrophy "threshold" is required to drive the addition of new myonuclei to existing muscle fibers. Methods Studies of resistance training endurance training with or without nutrient (i.e., protein) supplementation and steroid administration with measures of muscle fiber hypertrophy and myonuclei number as primary or secondary outcomes were considered. Twenty-seven studies incorporating 62 treatment groups and 903 subjects fulfilled the inclusion criteria and were included in the analyses. Results Muscle fiber hypertrophy of ≤10% induces increases in myonuclear content, although asignificantly higher number of myonuclei are observed when muscle hypertrophy is 22%. Additional analyses showed that age, sex, and muscle fiber type do not influence muscle fiber hypertrophy or myonuclei addition. Conclusions Although a more consistent myonuclei addition occurs when muscle fiber hypertrophy is > 22%, our results challenge the concept of a muscle hypertrophy threshold as significant myonuclei addition occurs with lower muscle hypertrophy (i.e., < 10%

Comparisons Between Low-intensity Resistance Training With Blood Flow Restriction And High-intensity Resistance Training On Quadriceps Muscle Mass And Strength In Elderly

Vechin, FC, Libardi, CA, Conceicao, MS, Damas, FR, Lixandrao, ME, Berton, RPB, Tricoli, VAA, Roschel, HA, Cavaglieri, CR, Chacon-Mikahil, MPT, and Ugrinowitsch, C. Comparisons between low-intensity resistance training with blood flow restriction and high-intensity resistance training on quadriceps muscle mass and strength in elderly. J Strength Cond Res 29(4): 1071-1076, 2015-High-intensity resistance training (HRT) has been recommended to offset age-related loss in muscle strength and mass. However, part of the elderly population is often unable to exercise at high intensities. Alternatively, lowintensity resistance training with blood flow restriction (LRTBFR) has emerged. The purpose of this study was to compare the effects of LRT-BFR and HRT on quadriceps muscle strength and mass in elderly. Twenty-three elderly individuals, 14 men and 9 women (age, 64.04 +/- 3.81 years; weight, 72.55 +/- 16.52 kg; height, 163 +/- 11 cm), undertook 12 weeks of training. Subjects were ranked according to their pretraining quadriceps cross-sectional area (CSA) values and then randomly allocated into one of the following groups: (a) control group, (b) HRT: 4 x 10 repetitions, 70-80% one repetition maximum (1RM), and (c) LRT-BFR: 4 sets (1 x 30 and 3 x 15 repetitions), 20-30% 1RM. The occlusion pressure was set at 50% of maximum tibial arterial pressure and sustained during the whole training session. Leg press 1RM and quadriceps CSA were evaluated at before and after training. A mixed-model analysis was performed, and the significance level was set at p <= 0.05. Both training regimes were effective in increasing pre-to post-training leg press 1RM (HRT:; similar to 54%, p < 0.001; LRT-BFR:; similar to 17%, p = 0.067) and quadriceps CSA (HRT: 7.9%, p < 0.001; LRT-BFR: 6.6%, p < 0.001); however, HRT seems to induce greater strength gains. In summary, LRT-BFR constitutes an important surrogate approach to HRT as an effective training method to induce gains in muscle strength and mass in elderly.2941071107

Time course of resistance training–induced muscle hypertrophy in the elderly

LixandrAo, ME, Damas, F, Chacon-Mikahil, MPT, Cavaglieri, CR, Ugrinowitsch, C, Bottaro, M, Vechin, FC, ConceicAo, MS, Berton, R, and Libardi, CA. Time course of resistance training-induced muscle hypertrophy in the elderly. J Strength Cond Res 30(1): 159-163, 2016Extended periods of resistance training (RT) induce muscle hypertrophy. Nevertheless, to date, no study has investigated the time window necessary to observe significant changes in muscle cross-sectional area (CSA) in older adults. Therefore, this study investigated the time course of muscle hypertrophy after 10 weeks (20 sessions) of RT in the elderly. Fourteen healthy older subjects were randomly allocated in either the RT (n: 6) or control group (n: 8). The RT was composed of 4 sets x 10 repetitions (70-80% 1 repetition maximum [1RM]) in a leg press machine. The time course of vastus lateralis muscle hypertrophy (CSA) was assessed on a weekly basis by mode-B ultrasonography. Leg press muscle strength was assessed by dynamic 1RM test. Our results demonstrated that the RT group increased leg press 1RM by 42% (p 0.05) after 10 weeks of training. Significant increases in vastus lateralis muscle CSA were observed only after 18 sessions of training (9 weeks; p 0.05; 7.1%). In conclusion, our training protocol promoted muscle mass accrual in older subjects, and this was only observable after 18 sessions of RT (9 weeks)301159163sem informaçã

Early- and later-phases satellite cell responses and myonuclear content with resistance training in young men

Satellite cells (SC) are associated with skeletal muscle remodelling after muscle damage and/or extensive hypertrophy resulting from resistance training (RT). We recently reported that early increases in muscle protein synthesis (MPS) during RT appear to be directed toward muscle damage repair, but MPS contributes to hypertrophy with progressive muscle damage attenuation. However, modulations in acute-chronic SC content with RT during the initial (1st-wk: high damage), early (3rd-wk: attenuated damage), and later (10th-wk: no damage) stages is not well characterized. Ten young men (27 ± 1 y, 23.6 ± 1.0 kg·m-2) underwent 10-wks of RT and muscle biopsies (vastus-lateralis) were taken before (Pre) and post (48h) the 1st (T1), 5th (T2) and final (T3) RT sessions to evaluate fibre type specific SC content, cross-sectional area (fCSA) and myonuclear number by immunohistochemistry. We observed RT-induced hypertrophy after 10-wks of RT (fCSA increased ~16% in type II, P < 0.04; ~8% in type I [ns]). SC content increased 48h post-exercise at T1 (~69% in type I [P = 0.014]; ~42% in type II [ns]), and this increase was sustained throughout RT (pre T2: ~65%, ~92%; pre T3: ~30% [ns], ~87%, for the increase in type I and II, respectively, vs. pre T1 [P < 0.05]). Increased SC content was not coupled with changes in myonuclear number. SC have a more pronounced role in muscle repair during the initial phase of RT than muscle hypertrophy resulted from 10-wks RT in young men. Chronic elevated SC pool size with RT is important providing proper environment for future stresses or larger fCSA increases

Comparisons between low-intensity resistance training with blood flow restriction and high-intensity resistance training on quadriceps muscle mass and strength in elderly

Comparisons between low-intensity resistance training with blood flow restriction and high-intensity resistance training on quadriceps muscle mass and strength in elderly. J Strength Cond Res 29(4): 1071-1076, 2015-High-intensity resistance training (HRT) has been recommended to offset age-related loss in muscle strength and mass. However, part of the elderly population is often unable to exercise at high intensities. Alternatively, lowintensity resistance training with blood flow restriction (LRTBFR) has emerged. The purpose of this study was to compare the effects of LRT-BFR and HRT on quadriceps muscle strength and mass in elderly. Twenty-three elderly individuals, 14 men and 9 women (age, 64.04 +/- 3.81 years; weight, 72.55 +/- 16.52 kg; height, 163 +/- 11 cm), undertook 12 weeks of training. Subjects were ranked according to their pretraining quadriceps cross-sectional area (CSA) values and then randomly allocated into one of the following groups: (a) control group, (b) HRT: 4 x 10 repetitions, 70-80% one repetition maximum (1RM), and (c) LRT-BFR: 4 sets (1 x 30 and 3 x 15 repetitions), 20-30% 1RM. The occlusion pressure was set at 50% of maximum tibial arterial pressure and sustained during the whole training session. Leg press 1RM and quadriceps CSA were evaluated at before and after training. A mixed-model analysis was performed, and the significance level was set at p <= 0.05. Both training regimes were effective in increasing pre-to post-training leg press 1RM (HRT:; similar to 54%, p < 0.001; LRT-BFR:; similar to 17%, p = 0.067) and quadriceps CSA (HRT: 7.9%, p < 0.001; LRT-BFR: 6.6%, p < 0.001); however, HRT seems to induce greater strength gains. In summary, LRT-BFR constitutes an important surrogate approach to HRT as an effective training method to induce gains in muscle strength and mass in elderly.2941071107

Aerobic exercise-induced changes in cardiorespiratory fitness in breast cancer patients receiving chemotherapy : A systematic review and meta-analysis

While performing aerobic exercise during chemotherapy has been proven feasible and safe, the efficacy of aerobic training on cardiorespiratory fitness (CRF) in women with breast cancer undergoing chemotherapy has not yet been systematically assessed. Therefore, the objective of this work was to determine (a) the efficacy of aerobic training to improve CRF; (b) the role of aerobic training intensity (moderate or vigorous) on CRF response; (c) the effect of the aerobic training mode (continuous or interval) on changes in CRF in women with breast cancer (BC) receiving chemotherapy. A systematic review and meta-analysis were conducted as per PRISMA guidelines, and randomized controlled trials comparing usual care (UC) and aerobic training in women with BC undergoing chemotherapy were eligible. The results suggest that increases in CRF are favored by (a) aerobic training when compared to usual care; (b) vigorous-intensity aerobic exercise (64–90% of maximal oxygen uptake, VO2max) when compared to moderate-intensity aerobic exercise (46–63% of VO2max); and (c) both continuous and interval aerobic training are effective at increasing the VO2max. Aerobic training improves CRF in women with BC undergoing chemotherapy. Notably, training intensity significantly impacts the VO2max response. Where appropriate, vigorous intensity aerobic training should be considered for women with BC receiving chemotherapy

Low-intensity resistance training with partial blood flow restriction and high-intensity resistance training induce similar changes in skeletal muscle transcriptome in elderly humans

We aimed to investigate the mechanisms underlying muscle growth after 12 weeks of resistance training performed with blood flow restriction (RT-BFR) and high-intensity resistance training (HRT) in older individuals. Participants were allocated into the following groups: HRT, RT-BFR, or a control group. High-throughput transcriptome sequencing was performed by the Illumina HiSeq 2500 platform. HRT and RT-BFR presented similar increases in the quadriceps femoris cross-sectional area, and few genes were differently expressed between interventions. The small differences in gene expression between interventions suggest that similar mechanisms may underpin training-induced muscle growth442216220sem informaçãosem informaçã

Representative image of the immunofluorescent stain.

<p>(a) MHCI/Laminin; (b) MHCII; (c) DAPI; (d) Pax7; and (e) MHCI/Laminin/MHCII/Pax7 (Merge). Arrows denotes SC (upper arrow: SC cell associated with a type II fibre; lower arrow: SC cell associated with a type I fibre).</p