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1.
Purpose: The purpose of this study was to investigate the physiological adaptations of resistance training (RT) in prepubertal boys. Methods: Eighteen healthy boys were divided into RT (n = 9, Mage = 10.4 ± 0.5 years) and control (CTR; n = 9, Mage = 10.9 ± 0.7 years) groups. The RT group underwent a resistance training during 12 weeks, 3 times per week, performing 3 sets of 6 to 15 repetitions at intensities ranging from 60% to 80% of maximal dynamic strength (1-repetition maximum [1-RM] values). Before and after the training, the groups were assessed in their body mass and composition (dual-energy X-ray absorptiometry), isokinetic dynamometry, 1-RM, and ergoespirometry. Moreover, force per unit of muscle volume was calculated by the quotient between 1-RM and lean mass. Results: Both groups presented statistically significant (p < .05) increases in the 1-RM and force per unit of muscle volume in the knee extension and elbow flexion, but these strength increases were statistically significantly greater in the RT group (effect size [ES] = 2.83–9.00) than in the CTR group (ES = 0.72–1.00). Moreover, both groups statistically significantly increased in lean body mass variables (ES = 0.12–0.38). However, increases in the fat mass variables occurred only in the CTR group (ES = ? 0.01–0.50), whereas no changes were observed in the RT group. Furthermore, there were statistically significant increases in all bone mineral content variables (ES = 0.13–0.43), without differences between groups. No cardiorespiratory changes were observed. Conclusion: Twelve weeks of RT was effective in improving strength and force per unit of muscle volume and prevented fat mass increases in boys.  相似文献   

2.
The aim of this study was to analyze the effects of resistance training (RT) performed with 1 or 3 sets per exercise on osteosarcopenic obesity (OSO) syndrome parameters in older women. Sixty-two older women (68.0 ± 4.3 years, 26.8 ± 4.4 kg/m2) participated in a 12-week RT program. Participants were randomly assigned into one of the three groups: two training groups that performed either 1 set (G1S, n = 21) or 3 sets (G3S, n = 20) 3 times weekly, or a control group (CG, n = 21). Body composition was assessed by dual X-ray absorptiometry, strength was evaluated by 1 repetition maximum testing. The G3S presented significantly higher strength changes than G1S. The changes for percentage of body fat were higher for G3S compared to G1S. There was no difference in skeletal muscle mass between G3S and G1S, however both training groups displayed greater increases in this outcome compared to CG. There was no effect for bone mineral density. The overall analysis indicated higher (P < 0.05) positive changes for G3S than G1S (composed Z-score: G3S = 0.62 ± 0.40; G1S = 0.11 ± 0.48). The results suggest that a 12-week RT period is effective to improve the risk factors of OSO, and that 3 sets induce higher improvements than a single set.  相似文献   

3.
The aim of the study was to compare the effect of resistance training (RT) frequencies of five times (RT5), thrice- (RT3) or twice- (RT2) weekly in muscle strength and hypertrophy in young men. Were used a within-subjects design in which 20 participants had one leg randomly assigned to RT5 and the other to RT3 or to RT2. 1?RM and muscle cross-sectional area (CSA) were assessed at baseline, after four (W4) and eight (W8) RT weeks. RT5 resulted in greater total training volume (TTV) than RT3 and RT2 (P?=?.001). 1?RM increased similarly between protocols at W4 (RT5: 55?±?9?Kg, effect size (ES): 1.18; RT3: 51?±?11?Kg, ES: 0.80; RT2: 54?±?7?Kg, ES: 1.13; P?P?2, ES: 0.54; RT3: 22.0?±?4.6?cm2, ES: 0.19; RT2: ES: 0.25; 23.8?±?3.8?cm2; P?2; ES: 0.69; RT3: 23.6?±?4.2?cm2, ES: 0.58; RT2: 25.5?±?3.7?cm2; ES: 0.70; P?2; RT3: 21.2?±?4.0?cm2; RT2: 22.9?±?3.8?cm2). Performing RT5, RT3 and RT2 a week result in similar muscle strength increase and hypertrophy, despite higher TTV for RT5.  相似文献   

4.
Purpose: Acute muscle damage after exercise triggers subsequent regeneration, leading to hypertrophy and increased strength after repeated exercise. It has been debated whether acute exercise-induced muscle damage is altered under various premenopausal estrogen conditions. Acute contraction-induced muscle damage was compared during exogenous (oral contraceptive, OC), endogenous (luteal phase, HI), or low (menses, LO) estrogen in healthy young women aged 21 to 30 years old. Methods: Women (OC, n = 9; HI, n = 9; LO, n = 8; total N = 26) performed 1 neuromuscular electrical stimulation (NMES) bout. Soreness, measured via visual analog scale and the Likert Scale of Muscle Soreness for Lower Limb (LSMSLL), quadriceps strength, and plasma myoglobin (Mb), interleukin (IL)-6, IL-8, and granulocyte-colony stimulating factor were measured before and after NMES. Results: NMES performance was similar across groups. Meaningful within-group increases in Mb (effect size [ES] = 1.12) and IL-8 (ES = 0.38) occurred in LO; ES for HI and OC were trivial. ES of the between-group difference in change was moderate for Mb (LO vs. HI = 1.15) and IL-8 (LO vs. HI = 0.86; LO vs. OC = 0.73). 17-β estradiol correlated moderately and negatively with Mb relative change (r = –.52, p < .05). LO had ~5% greater strength loss than OC and HI. The mean change score for the LSMSLL 2 days post-NMES was clinically greater in LO than OC or HI. Conclusions: Acute NMES-induced indicators of muscle fiber damage and qualitative muscle soreness may be attenuated during the luteal phase or active OC pill consumption compared with the menstrual phase.  相似文献   

5.
Abstract

The purpose of this study was to establish if vertical stiffness was greater in professional Australian rules footballers who sustained a lower limb skeletal muscle strain compared to those who did not, and to establish if a relationship between age, or training history, and vertical stiffness existed. Thirty-one participants underwent weekly rebound jump testing on a force platform over two seasons. Vertical stiffness was calculated for injured players and the uninjured cohort 1 and 3 weeks prior to sustaining an injury and at the end of preseason. Eighteen athletes were in the “uninjured” cohort and 13 in the “injured” cohort. No significant difference in vertical stiffness was observed between groups (P = 0.18 for absolute stiffness; P = 0.08 for stiffness relative to body mass), within groups (P = 0.83 and P = 0.88, respectively) or for a time*cohort interaction (P = 0.77 and P = 0.80, respectively). No relationship between age and vertical stiffness existed (r = ?0.06 for absolute and relative stiffness), or training history and vertical stiffness (r = ?0.01 and 0.00 for absolute and relative stiffness, respectively) existed. These results and others lend to suggest that vertical stiffness is not related to lower limb muscle strain injury.  相似文献   

6.
Two experiments (n = 10) were conducted to determine the effects of roller massager (RM) on ankle plantar flexor muscle recovery after exercise-induced muscle damage (EIMD). Experiment 1 examined both functional [i.e., ankle plantar flexion maximal isometric contraction and submaximal (30%) sustained force; ankle dorsiflexion maximal range of motion and resistance to stretch; and medial gastrocnemius pain pressure threshold] and morphological [cross-sectional area, thickness, fascicle length, and fascicle angle] variables, before and immediately, 1, 24, 48, and 72 h after an EIMD stimulus. Experiment 2 examined medial gastrocnemius deoxyhaemoglobin concentration kinetics before and 48 h after EIMD. Participants performed both experiments twice: with (RM) and without (no-roller massager; NRM) the application of a RM (6 × 45 s; 20-s rest between sets). RM intervention did not alter the functional impairment after EIMD, as well as the medial gastrocnemius morphology and oxygenation kinetics (P > 0.05). Although, an acute increase of ipsilateral (RM = + 19%, NRM = ?5%, P = 0.032) and a strong tendency for contralateral (P = 0.095) medial gastrocnemius pain pressure threshold were observed. The present results suggest that a RM has no effect on plantar flexors performance, morphology, and oxygenation recovery after EIMD, except for muscle pain pressure threshold (i.e., a soreness).  相似文献   

7.
This study examined the mechanomyographic (MMGRMS) amplitude–force relationships for 5 (age = 19.20 ± 0.45 years) aerobically trained (AT), 5 (age = 25 ± 4.53 years) resistance-trained (RT) and 5 (age = 21.20 ± 2.17 years) sedentary (SED) individuals. Participants performed an isometric trapezoidal muscle action at 60% maximal voluntary contraction of the leg extensors that included linearly increasing, steady force, and linearly decreasing muscle actions. MMG and skinfold thickness were recorded from the vastus lateralis. b and a terms were calculated from the natural log-transformed MMGRMS–force relationships (linearly increasing and decreasing segments) for each participant. An average of MMGRMS was calculated for the entire steady force segment. The b terms for the RT (0.727 ± 0.334) and SED (0.622 ± 0.281) were significantly greater (P < 0.05) than the AT (0.159 ± 0.223) and were greater during the linearly increasing (0.622 ± 0.426) than decreasing (0.383 ± 0.269) segments when collapsed across segments and training status, respectively. MMGRMS during the steady force segment and skinfold thicknesses were not different among training statuses (P = 0.106, P = 0.142). Motor unit (MU) activation strategies were influenced as a function of exercise training status and muscle action. Future research is needed to fully understand the implications of these changes in MU control strategies as a result of chronic exercise training on exercise and athletic performance.  相似文献   

8.
The purpose of this study was to examine the effect of a 12-week resistance training programme on fat-free mass (FFM), muscle cross-sectional area, muscular strength and muscle quality in women who underwent Roux-en-Y gastric bypass surgery. Participants were 16 women (mean age = 44.9 ± 10.2 years) from bariatric surgical groups who were randomly assigned into either a control or an intervention group. Air displacement plethysmography measured FFM and magnetic resonance imaging measured quadriceps muscle cross-sectional area and whole thigh muscle cross-sectional area. Muscular strength and quality was assessed using an estimated 1-Repetition Maximum assessment. All measurements were collected twice, at baseline and at a 12-week follow-up. There were significantly greater improvements in leg press strength (mean differences = 55.4%, P < 0.001, Cohen’s d = 2.4), leg extension strength (mean differences = 18.0%, P = 0.014, Cohen’s d = 0.86) and leg press muscle quality (mean differences = 54.5%, P < 0.001, Cohen’s d = 1.9) in the intervention group compared to the control group following the resistance training programme. The resistance training intervention significantly improved muscular strength and quality; however, it did not illicit changes in FFM or muscle cross-sectional area in women who underwent Roux-en-Y gastric bypass surgery.  相似文献   

9.
Abstract

This study was undertaken to examine the acute effect of interferential current on mechanical pain threshold and isometric peak torque after delayed onset muscle soreness induction in human hamstrings. Forty-one physically active healthy male volunteers aged 18?33 years were randomly assigned to one of two experimental groups: interferential current group (n = 21) or placebo group (n = 20). Both groups performed a bout of 100 isokinetic eccentric maximal voluntary contractions (10 sets of 10 repetitions) at an angular velocity of 1.05 rad · s?1 (60° · s?1) to induce muscle soreness. On the next day, volunteers received either an interferential current or a placebo application. Treatment was applied for 30 minutes (4 kHz frequency; 125 μs pulse duration; 80?150 Hz bursts). Mechanical pain threshold and isometric peak torque were measured at four different time intervals: prior to induction of muscle soreness, immediately following muscle soreness induction, on the next day after muscle soreness induction, and immediately after the interferential current and placebo application. Both groups showed a reduction in isometric torque (P < 0.001) and pain threshold (P < 0.001) after the eccentric exercise. After treatment, only the interferential current group showed a significant increase in pain threshold (P = 0.002) with no changes in isometric torque. The results indicate that interferential current was effective in increasing hamstrings mechanical pain threshold after eccentric exercise, with no effect on isometric peak torque after treatment.  相似文献   

10.
The relative effects of resistance training (RT) upon muscle fitness and immune function among HIV-infected patients are uncertain. The purpose of this study was to perform a meta-analysis to determine the effects of RT upon muscle strength, muscle mass and CD4 cells count and to identify potential moderators of those outcomes in HIV-infected patients. Meta-analyses use random or fixed-effects model depending on the heterogeneity of effect sizes, complemented with Hedge’s g correction factor. Thirteen trials were meta-analysed. Overall, RT increased muscle strength (35.5%, P < 0.01) and CD4 cell count (26.1%, P = 0.003) versus controls (P < 0.03), but not muscle mass (P = 0.051). Meta-regression followed by subgroup moderator analysis showed that gains in muscle strength followed a dose–response pattern with largest increase detected among trials with longer (24 weeks; 49.3%) than shorter intervention (<12 weeks; 39%), higher (Physiotherapy Evidence-Based Database [PEDro] scale = 6; 38.3%) than lower (PEDro = 5; 28.1%) quality, and longer (12 months; 59.7%) than shorter time under highly active antiretroviral therapy (HAART) (<6 months; 37.1%), (P < 0.01). RT appears to be efficacious to improve muscular strength (~35.5%) and CD4 cell count (~26.1%), but not muscle mass of HIV-infected patients. Effects upon strength were greater in studies with higher quality and among trials with longer RT and HAART.  相似文献   

11.
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12.
The purpose of this systematic review and meta-analysis is to assess the effect of concurrent high intensity interval training (HIIT) and resistance training (RT) on strength and hypertrophy. Five electronic databases were searched using terms related to HIIT, RT, and concurrent training. Effect size (ES), calculated as standardised differences in the means, were used to examine the effect of concurrent HIIT and RT compared to RT alone on muscle strength and hypertrophy. Sub-analyses were performed to assess region-specific strength and hypertrophy, HIIT modality (cycling versus running), and inter-modal rest responses. Compared to RT alone, concurrent HIIT and RT led to similar changes in muscle hypertrophy and upper body strength. Concurrent HIIT and RT resulted in a lower increase in lower body strength compared to RT alone (ES = ?0.248, p = 0.049). Sub analyses showed a trend for lower body strength to be negatively affected by cycling HIIT (ES = ?0.377, p = 0.074) and not running (ES = ?0.176, p = 0.261). Data suggests concurrent HIIT and RT does not negatively impact hypertrophy or upper body strength, and that any possible negative effect on lower body strength may be ameliorated by incorporating running based HIIT and longer inter-modal rest periods.  相似文献   

13.
This study aims to (1) determine whether isometric training at a short vs. long quadriceps muscle length affects concentric torque production; (2) examine the relationship between muscle hypertrophy and concentric torque; and (3) determine whether changes in fascicle length are associated with changes in concentric torque.

Sixteen men performed isometric training at a short (SL, n = 8) or a long muscle length (LL, n = 8). Changes in maximal concentric torque were measured at 30, 60, 90, 120, 180, 240 and 300 rad · s?1. The relationships between the changes in concentric torque, cross-sectional area, volume and fascicle length were tested.

Concentric torque increased significantly after training only in LL and at angular velocities of 30 and 120 rad · s?1 by 12–13% (P < 0.05). Muscle size increased in LL only, the changes were correlated (r = 0.73–0.93, P < 0.05) with the changes in concentric torque. Vastus lateralis (VL) fascicle length increased in both groups (5.4 ± 4.9%, P = 0.001) but the change was not correlated with changes in concentric torque in either group.

Isometric training-induced increases in muscle size and concentric torque were best elicited by training at long muscle lengths. These results highlight a clear muscle length dependence of isometric training on dynamic torque production.  相似文献   

14.
Abstract

The aim of this study was to examine the effect of concentric warm-up exercise on eccentrically induced changes in muscle strength, range of motion, and soreness of the elbow flexors. Ten resistance-exercise naïve participants performed intermittent incremental eccentric actions (42 in total) of the elbow flexor muscles of each arm to induce muscle damage. The arms of each participant were randomly assigned either to a pre-eccentric exercise warm-up involving intermittent concentric exercise (warm-up) or no prior exercise (control). Strength, range of motion, and ratings of soreness were recorded before and 1, 2, 3, 4, and 7 days after exercise. Strength, range of motion, and soreness during muscular movements changed over time (P at most 0.01; Cohen's d at least 0.51, medium). There was an interaction (P < 0.001) for strength, showing a smaller reduction after exercise for warm-up than control (P < 0.001, d = 2.44, large effect). The decreased range of motion was less for warm-up than control for the arm while extended (P < 0.001), flexed (P = 0.002), and relaxed (P = 0.004). Muscle soreness was reduced for the warm-up group, while the muscle was flexed, extended, and relaxed compared with control (P < 0.001). The results demonstrate that a concentric warm-up exercise attenuates the reduction in loss of strength, range of motion, and muscle soreness after eccentric-exercise-induced muscle damage and might allow higher intensities of training to be performed.  相似文献   

15.
Abstract

The purpose of this study was to assess the effects of heavy resistance, explosive resistance, and muscle endurance training on neuromuscular, endurance, and high-intensity running performance in recreational endurance runners. Twenty-seven male runners were divided into one of three groups: heavy resistance, explosive resistance or muscle endurance training. After 6 weeks of preparatory training, the groups underwent an 8-week resistance training programme as a supplement to endurance training. Before and after the 8-week training period, maximal strength (one-repetition maximum), electromyographic activity of the leg extensors, countermovement jump height, maximal speed in the maximal anaerobic running test, maximal endurance performance, maximal oxygen uptake ([Vdot]O2max), and running economy were assessed. Maximal strength improved in the heavy (P = 0.034, effect size ES = 0.38) and explosive resistance training groups (P = 0.003, ES = 0.67) with increases in leg muscle activation (heavy: P = 0.032, ES = 0.38; explosive: P = 0.002, ES = 0.77). Only the heavy resistance training group improved maximal running speed in the maximal anaerobic running test (P = 0.012, ES = 0.52) and jump height (P = 0.006, ES = 0.59). Maximal endurance running performance was improved in all groups (heavy: P = 0.005, ES = 0.56; explosive: P = 0.034, ES = 0.39; muscle endurance: P = 0.001, ES = 0.94), with small though not statistically significant improvements in [Vdot]O2max (heavy: ES = 0.08; explosive: ES = 0.29; muscle endurance: ES = 0.65) and running economy (ES in all groups < 0.08). All three modes of strength training used concurrently with endurance training were effective in improving treadmill running endurance performance. However, both heavy and explosive strength training were beneficial in improving neuromuscular characteristics, and heavy resistance training in particular contributed to improvements in high-intensity running characteristics. Thus, endurance runners should include heavy resistance training in their training programmes to enhance endurance performance, such as improving sprinting ability at the end of a race.  相似文献   

16.
Abstract

The aim of this study was to assess the effects of cold-water immersion (cryotherapy) on indices of muscle damage following a bout of prolonged intermittent exercise. Twenty males (mean age 22.3 years, s = 3.3; height 1.80 m, s = 0.05; body mass 83.7 kg, s = 11.9) completed a 90-min intermittent shuttle run previously shown to result in marked muscle damage and soreness. After exercise, participants were randomly assigned to either 10 min cold-water immersion (mean 10°C, s = 0.5) or a non-immersion control group. Ratings of perceived soreness, changes in muscular function and efflux of intracellular proteins were monitored before exercise, during treatment, and at regular intervals up to 7 days post-exercise. Exercise resulted in severe muscle soreness, temporary muscular dysfunction, and elevated serum markers of muscle damage, all peaking within 48 h after exercise. Cryotherapy administered immediately after exercise reduced muscle soreness at 1, 24, and 48 h (P < 0.05). Decrements in isometric maximal voluntary contraction of the knee flexors were reduced after cryotherapy treatment at 24 (mean 12%, s x  = 4) and 48 h (mean 3%, s x  = 3) compared with the control group (mean 21%, s x  = 5 and mean 14%, s x  = 5 respectively; P < 0.05). Exercise-induced increases in serum myoglobin concentration and creatine kinase activity peaked at 1 and 24 h, respectively (P < 0.05). Cryotherapy had no effect on the creatine kinase response, but reduced myoglobin 1 h after exercise (P < 0.05). The results suggest that cold-water immersion immediately after prolonged intermittent shuttle running reduces some indices of exercise-induced muscle damage.  相似文献   

17.
The purpose of the current study was to examine the effect of 6 weeks of whole body vibration training (WBVT) on body composition, muscle activity of the gastrocnemius and vastus lateralis, gastrocnemius muscle architecture (static and dynamic) and ground reaction forces (performance jump) during the take-off phase of a countermovement jump in young healthy adult males. A total of 33 men (23.31 ± 5.62 years) were randomly assigned to a whole body vibration group (experimental group, EGWBVT: n = 17; 22.11 ± 4.97 years) or a control group (CG: n = 16; 24.5 ± 6.27 years). The total duration of the intervention phase (WBVT) was 6 weeks with a frequency of 3 sessions per week. Statistically significant differences were observed (P ≤ 0.05) between pre- and post-test in the power peak (Δ 1.91 W · kg?1; P = 0.001), take-off velocity (0.1 cm · s?1; P = 0.002) and jump height (Δ 0.4 cm; P = 0.002) for EGWBVT. There were no statistically significant differences in any of the body composition and muscle architecture variables. Moreover, no significant differences were found between EGWBVT and CG nor changes in muscle activity during take-off phase of the gastrocnemius and vastus lateralis pre- versus post-training. This study suggests that a 6-week WBVT programme with increasing intensity improves jump performance but does not alter muscle activity nor muscle architecture in healthy young men.  相似文献   

18.
The purpose of the present study was to characterise the relationship between relative versus absolute internal and external loads in collegiate basketball players throughout the course of a season. Five Division I basketball players wore triaxial accelerometers throughout the 2015–2016 season and were tensiomyographically assessed weekly. One-way repeated-measure analysis of variance (RM ANOVA) with least-significant-difference (LSD) pairwise comparisons was used to determine which absolute weekly loads were different across the season. Cohen’s d was used to supplement the determination of meaningful relative load changes. Overall RM ANOVA models suggest absolute external load differences occurred (PlayerLoad? F = 17.63; IMA? F = 31.63). Two-way RM ANOVA models revealed main effect differences were revealed between muscle groups for Tc (F = 9.11) and Dm (F = 3.25). Meaningful relative load changes between weeks were observed for both external and internal. The present study observed that tensiomyography utilised as a tool to monitor internal load may be more suitable for detecting fatigue from relative external load changes versus absolute load attained. Limiting weekly training volume changes to ≤10% may maintain appropriate adaptation. Mediolateral plane IMA? and adductor longus muscle group may be pertinent metrics when monitoring female collegiate basketball athletes.  相似文献   

19.
ABSTRACT

The main purpose of this study was to compare the effects of resistance training (RT) performed with different training volumes on phase angle (PhA), body water components, and muscle quality (MQ) in untrained older adult women. A second purpose was to assess the relationship between PhA and MQ. Sixty-two older adult women (68.6 ± 5.0 years, 65.2 ± 13.3 kg, 156.1 ± 6.2 cm) were randomly assigned into one of the three groups: two training groups performed either 1 set (G1S) or 3 sets (G3S), or a control group (CG). Body water components and PhA were estimated by bioelectrical impedance (BIA). MQ was determined by dividing skeletal muscle mass estimated by dual-energy absorptiometry (DXA) by total muscle strength from three exercises. After the intervention period, both training groups demonstrated improvements (P < 0.05) when compared with CON for intracellular water, total body water, PhA, and MQ. These results suggest that RT can improve PhA, body water components, and MQ after 12 weeks of RT in untrained older women, regardless of training volume. Furthermore, changes in MQ were positively correlated with changes in PhA (r = 0.60, P < 0.01).  相似文献   

20.
Abstract

The aims of this study were to examine age and sex differences in elbow extensor and flexor anatomical muscle cross-sectional area (mCSA) measured by magnetic resonance imaging (MRI) and the location of maximal mCSA as a percentage of the distance from the distal to the proximal end of the humerus. Ninety-five individuals spread across the age groups 9 – 10 years, 16 – 17 years and 21 years participated in the study. Muscle cross-sectional area derived from the manual MRI tracing proved to be highly reliable in terms of limits of agreement (?2.5 to 1.5 cm2) and the intraclass correlation coefficient (ICC = 0.998). A sex-by-age group analysis of variance revealed significant effects (P < 0.01) of sex, group and a sex-by-group interaction, the latter reflecting a greater increase in males than females of upper arm mCSA from childhood to adulthood. Extensor mCSA was more proximal (55 ± 6%) than that of the flexors (28 ± 6%). A significant effect (P < 0.01) of group was found for location of maximal extensor mCSA, reflecting its more distal position with increasing age. Measurements of muscle size should be made at the individually determined position of maximal mCSA if interpreting data collected during growth and maturation, especially if the muscle group of interest is the elbow extensors and if different age groups are being monitored.  相似文献   

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