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Concept: Isometric exercise

427

We performed a systematic review, meta-analysis and meta-regression to determine if dietary protein supplementation augments resistance exercise training (RET)-induced gains in muscle mass and strength.

Concepts: Nutrition, Muscle, Physical exercise, Exercise, Strength training, Weight training, Meta-analysis, Isometric exercise

171

BACKGROUND: Sympathetic nervous activity contributes to the maintenance of muscle oxygenation. However, patients with chronic pain may suffer from autonomic dysfunction. Furthermore, insufficient muscle oxygenation is observed among workers with chronic neck and shoulder pain. The aim of our study was to investigate how muscle load tasks affect sympathetic nervous activity and changes in oxygenation of the trapezius muscles in subjects with chronic neck and shoulder pain. METHODS: Thirty females were assigned to two groups: a pain group consisting of subjects with chronic neck and shoulder pain and a control group consisting of asymptomatic subjects. The participants performed three sets of isometric exercise in an upright position; they contracted their trapezius muscles with maximum effort and let the muscles relax (Relax). Autonomic nervous activity and oxygenation of the trapezius muscles were measured by heart rate variability (HRV) and Near-Infrared Spectroscopy. RESULTS: Oxyhemoglobin and total hemoglobin of the trapezius muscles in the pain group were lower during the Relax period compared with the control group. In addition, the low frequency / high frequency (LF/HF) ratio of HRV significantly increased during isometric exercise in the control group, whereas there were no significant changes in the pain group. CONCLUSIONS: Subjects with neck and shoulder pain showed lower oxygenation and blood flow of the trapezius muscles responding to isometric exercise, compared with asymptomatic subjects. Subjects with neck and shoulder pain also showed no significant changes in the LF/HF ratio of HRV responding to isometric exercise, which would imply a reduction in sympathetic nervous activity.

Concepts: Energy, Muscle, Muscle contraction, Acetylcholine, Autonomic nervous system, Isometric exercise, Trapezius muscle, Clavicle

54

Cross education (CE) occurs after unilateral training whereby performance of the untrained contralateral limb is enhanced. A few studies have shown that CE can preserve or “spare” strength and size of an opposite immobilized limb, but the specificity (i.e., trained homologous muscle and contraction type) of these effects is unknown. The purpose was to investigate specificity of CE “sparing” effects with immobilization. The nondominant forearm of 16 participants was immobilized with a cast, and participants were randomly assigned to a resistance training (eccentric wrist flexion, 3 times/week) or control group for 4 weeks. Pre- and posttesting involved wrist flexors and extensors eccentric, concentric and isometric maximal voluntary contractions (via dynamometer), muscle thickness (via ultrasound), and forearm muscle cross-sectional area (MCSA; via peripheral quantitative computed tomography). Only the training group showed strength preservation across all contractions in the wrist flexors of the immobilized limb (training: -2.4% vs. control: -21.6%; P = 0.04), and increased wrist flexors strength of the nonimmobilized limb (training: 30.8% vs. control: -7.4%; P = 0.04). Immobilized arm MCSA was preserved for the training group only (training: 1.3% vs. control: -2.3%; P = 0.01). Muscle thickness differed between groups for the immobilized (training: 2.8% vs. control: -3.2%; P = 0.01) and nonimmobilized wrist flexors (training: 7.1% vs. control: -3.7%; P = 0.02). Strength preservation was nonspecific to contraction type ( P = 0.69, [Formula: see text] = 0.03) yet specific to the trained flexors muscle. These findings suggest that eccentric training of the nonimmobilized limb can preserve size of the immobilized contralateral homologous muscle and strength across multiple contraction types. NEW & NOTEWORTHY Unilateral strength training preserves strength, muscle thickness, and muscle cross-sectional area in an opposite immobilized limb. The preservation of size and strength was confined to the trained homologous muscle group. However, strength was preserved across multiple contraction types.

Concepts: Muscle, Muscle contraction, Strength training, Forearm, Upper limb, Wrist, Isometric exercise, Preservation

38

To compare the effects of a periodic resistance training (PTR) program with those of a continuous resistance training (CTR) program on muscle size and function, 14 young men were randomly divided into a CTR group and a PTR group. Both groups performed high-intensity bench press exercise training [75 % of one repetition maximum (1-RM); 3 sets of 10 reps] for 3 days per week. The CTR group trained continuously over a 24-week period, whereas the PTR group performed three cycles of 6-week training (or retraining), with 3-week detraining periods between training cycles. After an initial 6 weeks of training, increases in cross-sectional area (CSA) of the triceps brachii and pectoralis major muscles and maximum isometric voluntary contraction of the elbow extensors and 1-RM were similar between the two groups. In the CTR group, muscle CSA and strength gradually increased during the initial 6 weeks of training. However, the rate of increase in muscle CSA and 1-RM decreased gradually after that. In the PTR group, increase in muscle CSA and strength during the first 3-week detraining/6-week retraining cycle were similar to that in the CTR group during the corresponding period. However, increase in muscle CSA and strength during the second 3-week detraining/6-week retraining cycle were significantly higher in the PTR group than in the CTR group. Thus, overall improvements in muscle CSA and strength were similar between the groups. The results indicate that 3-week detraining/6-week retraining cycles result in muscle hypertrophy similar to that occurring with continuous resistance training after 24 weeks.

Concepts: Exercise, Triceps brachii muscle, Muscle contraction, Menstrual cycle, Strength training, Isometric exercise, Bench press, Pectoralis major muscle

38

Hartmann, H, Wirth, K, Klusemann, M, Dalic, J, Matuschek, C, and Schmidtbleicher, D. Influence of squatting depth on jumping performance. J Strength Cond Res 26(12): 3243-3261, 2012-It is unclear if increases in 1 repetition maximum (1RM) in quarter squats result in higher gains compared with full depth squats in isometric force production and vertical jump performance. The aim of the research projects was to compare the effects of different squat variants on the development of 1RM and their transfer effects to Countermovement jump (CMJ) and squat jump (SJ) height, maximal voluntary contraction (MVC), and maximal rate of force development (MRFD). Twenty-three women and 36 men (mean age: 24.11 ± 2.88 years) were parallelized into 3 groups based on their CMJ height: deep front squats (FSQ, n = 20), deep back squats (BSQ, n = 20), and quarter back squats (BSQ¼, n = 19). In addition, a control group (C, n = 16) existed (mean age: 24.38 ± 0.50 years). Experimental groups trained 2 d·wk for 10 weeks with a strength-power block periodization, which produced significant (p ≤ 0.05) gains of the specific squat 1RM. The FSQ and BSQ attained significant (p ≤ 0.05) elevations in SJ and CMJ without any interaction effects between both groups (p ≥ 0.05). The BSQ¼ and C did not reveal any significant changes of SJ and CMJ. The FSQ and BSQ had significantly higher SJ scores over C (p ≤ 0.05). The BSQ did not feature any significant group difference to BSQ¼ (p = 0.116) in SJ, whereas FSQ showed a trend toward higher SJ heights over BSQ¼ (p = 0.052). The FSQ and BSQ presented significantly (p ≤ 0.05) higher CMJ heights over BSQ¼ and C. Posttest in MVC and MRFD demonstrated no significant changes for BSQ. Significant declines in MRFD for FSQ in the right leg (p ≤ 0.05) without any interaction effects for MVC and MRFD between both FSQ and BSQ were found. Training of BSQ¼ resulted in significantly (p ≤ 0.05) lower MRFD and MVC values in contrast to FSQ and BSQ. Quarter squat training elicited significant (p ≤ 0.05) transfer losses into the isometric maximal and explosive strength behavior. These findings therefore contest the concept of superior angle-specific transfer effects. Deep front and back squats guarantee performance-enhancing transfer effects of dynamic maximal strength to dynamic speed-strength capacity of hip and knee extensors compared with quarter squats.

Concepts: Muscle contraction, Strength training, Explosive material, Isometric exercise, Squatting, Physical strength, Strength, Squats

36

This study tested the hypothesis that chronic aerobic and resistance exercise (AE+RE) would elicit greater muscle hypertrophy than resistance exercise only (RE). Ten men (25 ± 4 yr) performed 5 wk unilateral knee extensor AE+RE. The opposing limb was subjected to RE. AE completed 6 hr prior to RE consisted of ∼45 min one-legged cycle ergometry. RE comprised 4 × 7 maximal concentric-eccentric knee extensions. Various indexes of in vivo knee extensor function were measured before and after training. Magnetic resonance imaging (MRI) assessed m. quadricep femoris (QF) cross-sectional area (CSA), volume, and signal intensity (SI). Biopsies obtained from m. vastus lateralis determined fiber CSA, enzyme levels, and gene expression of myostatin, atrogin-1, MuRF-1, PGC-1α, and VEGF. Increases (P < 0.05) in isometric strength and peak power, respectively, were comparable in AE+RE (9 and 29%) and RE (11 and 24%). AE+RE showed greater increase (14%; P < 0.05) in QF volume than RE (8%). Muscle fiber CSA increased 17% after AE+RE (P < 0.05) and 9% after RE (P > 0.05). QF SI increased (12%; P < 0.05) after AE+RE, but not RE. Neither AE+RE nor RE showed altered mRNA levels. Citrate synthase activity increased (P < 0.05) after AE+RE. The results suggest that the increased aerobic capacity shown with AE+RE was accompanied by a more robust increase in muscle size compared with RE. Although this response was not carried over to greater improvement in muscle function, it remains that intense AE can be executed prior to RE without compromising performance outcome.

Concepts: Muscle, Exercise, Magnetic resonance imaging, Knee, Strength training, Weight training, Exercise physiology, Isometric exercise

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The purpose of this study was to assess the effect of resistance training cessation on strength performance through a meta-analysis. Seven databases were searched from which 103 of 284 potential studies met inclusion criteria. Training status, sex, age, and the duration of training cessation were used as moderators. Standardized mean difference (SMD) in muscular performance was calculated and weighted by the inverse of variance to calculate an overall effect and its 95% confidence interval (CI). Results indicated a detrimental effect of resistance training cessation on all components of muscular performance: [submaximal strength; SMD (95% CI) = -0.62 (-0.80 to -0.45), P < 0.01], [maximal force; SMD (95% CI) = -0.46 (-0.54 to -0.37), P < 0.01], [maximal power; SMD (95% CI) = -0.20 (-0.28 to -0.13), P < 0.01]. A dose-response relationship between the amplitude of SMD and the duration of training cessation was identified. The effect of resistance training cessation was found to be larger in older people (> 65 years old). The effect was also larger in inactive people for maximal force and maximal power when compared with recreational athletes. Resistance training cessation decreases all components of muscular strength. The magnitude of the effect differs according to training status, age or the duration of training cessation.

Concepts: Old age, Probability theory, Strength training, Normal distribution, Effect size, Standard deviation, Isometric exercise, Dose-response relationship

32

Running economy (RE) has been seen to improve with concurrent strength and endurance training in young and elite endurance athletes. The purpose of the present study was to evaluate the effects of 2 different strength training protocols on RE and strength parameters in a group of regularly training master marathon runners. Sixteen participants were randomly assigned to a maximal strength training program (MST; n = 6; 44.2 ± 3.9 yrs), a resistance training (RT; n = 5; 44.8 ± 4.4 yrs) and a control group (CG; n = 5; 43.2 ± 7.9 yrs). Before and after the experimental period, resting metabolic rate, body composition, 1 repetition maximum, squat jump, countermovement jump and RE were evaluated. The MST group showed significant increases (p < 0.05) in 1RM (+16.34%) and RE (+6.17 %) at marathon pace. No differences emerged for the other groups (p > 0.05). Anthropometric data were unchanged after the training intervention (p > 0.05). Taken together, the results of this preliminary study indicate that master endurance athletes seem to benefit from concurrent strength and endurance training because the rate of force development may be crucial for RE improvement, one of the major determinants of endurance performance.

Concepts: Metabolism, Energy, Exercise, Strength training, Weight training, Aerobic exercise, Basal metabolic rate, Isometric exercise

31

The primary aim of this study was to determine whether chronic mental stress moderates recovery of muscular function and somatic sensations: perceived energy, fatigue and soreness, in a four-day period following a bout of strenuous resistance exercise. Undergraduate resistance training students (n = 31, age = 20.26 ± 1.34 y) completed the perceived stress scale (PSS) and Undergraduate Stress Questionnaire, measure of life event stress. At a later visit, they performed an acute heavy-resistance exercise protocol (10-RM leg press test plus six sets: 80-100% of 10-RM). Maximal isometric force (MIF), perceived energy, fatigue, and soreness were assessed in approximately 24-hour intervals post-exercise. Recovery data was analyzed with hierarchical linear modeling (HLM) growth curve analysis. Life event stress significantly moderated linear (p = .027) and squared (p = .031) recovery of MIF. This relationship held even when the model was adjusted for fitness, workload, and training experience. Perceived energy (p = .038), fatigue (p = .040) and soreness (p = .027) all were moderated by life stress. Mean perceived stress modulated linear and squared recovery of MIF (p values < .001) and energy (p = .004) but not fatigue or soreness. In all analyses, higher stress was associated with worse recovery. Stress, whether assessed as life event stress or perceived stress, moderated the recovery trajectories of muscular function and somatic sensations in a 96 hour period after strenuous resistance exercise. Therefore, under conditions of inordinate stress, individuals may need to be more mindful about observing an appropriate length of recovery.

Concepts: Exercise, Force, Strength training, Weight training, Stress, Isometric exercise

31

Keiner, M, Sander, A, Wirth, K, Caruso, O, Immesberger, P, and Zawieja, M. Strength performance in youth: trainability of adolescents and children in the back and front squats. J Strength Cond Res 27(2): 357-362, 2013-A basic question for many athletic coaches pertains to the maximum attainable strength level for youth athletes. The aim of this investigation was to establish reference values for the strength performance in the front and back squats in youth athletes. The strength performance in front and back squats of 141 elite youth soccer players was tested by a 1 repetition maximum (1RM) and 1RM related to bodyweight (SREL). The subjects aged between 11 and 19 years and were divided into 2 groups and 4 subgroups (A = younger than 19 years, B = younger than 17 years, C = younger than 15 years, and D = younger than 13 years). For approximately 2 years, one group (control group [CG]) only participated in routine soccer training and the other group (strength training group [STG]) participated in an additional strength training program along with the routine soccer training. Additionally, the strength performance in a 5RM in both squat variants of 105 young elite weightlifters (National Weightlifting Organization Baden Württemberg, [BWG]) was examined to show the high level of trainability of children and adolescents and to determine the reference strength values for young athletes. The STG performed in the parallel front squat SREL in the subgroups A 1.7 +/- 0.2, B 1.6 +/- 0.2, C 1.4 +/-0.2 and D 0.9 +/- 0.3. The STG had significantly (p < 0.001) higher strength values in 1RM and SREL than CG. The BWG had higher strength values than STG, but the BWG was not part of the statistical analysis because of the different test protocols (1RM vs. 5RM). Our data show that the SREL in parallel squat for young elite athletes with long-term training experience should be a minimum of 2.0 for 16- to 19-year-olds, 1.5 for 13- to 15-year-olds, and 0.7 for 11- to 12-year-olds.

Concepts: Group, Strength training, Weight training, The Parallel, Isometric exercise, Squatting, Physical strength, Weightlifting