SciCombinator

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Journal: Journal of strength and conditioning research / National Strength & Conditioning Association

51

The purpose of this study was to examine the effects of a crossfit-based high intensity power training (HIPT) program on aerobic fitness and body composition. Healthy subjects of both genders (23 males, 20 females) spanning all levels of aerobic fitness and body composition completed 10 weeks of HIPT consisting of lifts such as the squat, deadlift, clean, snatch, and overhead press performed as quickly as possible. Additionally, this crossfit-based HIPT program included skill work for the improvement of traditional Olympic lifts and selected gymnastic exercises. Body fat percentage was estimated using whole body plethysmography and maximal aerobic capacity (VO2max) was measured by analyzing expired gasses during a Bruce protocol maximal graded treadmill test. These variables were measured again following 10 weeks of training and compared for significant changes using a paired t-test. Results showed significant (P<0.05) improvements of VO2max in males (43.10±1.40 to 48.96±1.42 ml/kg/min) and females (35.98±1.60 to 40.22±1.62 ml/kg/min) as well as decreased body fat percentage in males (22.2±1.3 to 18.0±1.3) and females (26.6±2.0 to 23.2±2.0). These improvements were significant across all levels of initial fitness. Significant correlations between absolute oxygen consumption and oxygen consumption relative to body weight was found in both men (r=0.83, P<0.001) and women (r=0.94, P<0.001), indicating HIPT improved VO2max scaled to body weight independent of changes to body composition. Our data shows that HIPT significantly improves VO2max and body composition in subjects of both genders across all levels of fitness.

Concepts: Body plethysmography, Adipose tissue, Health, Exercise physiology, Better, Improve

41

The purpose of this project was to further elucidate the effects post-exercise alcohol ingestion. This project had many novel aspects including using a resistance exercise (RE) only exercise design and the inclusion of women. Ten resistance trained men and nine resistance trained women completed two identical acute heavy resistance exercise trials (six sets of Smith machine squats) followed by ingestion of either alcohol or placebo. All participants completed both conditions. Prior to exercise (PRE) and three (+3h) and five (+5h) hours post exercise, muscle tissue samples were obtained from the vastus lateralis by biopsies. Muscle samples were analyzed for phosphorylated mTORC1, S6K1, and 4E-BP1. For men, there was a significant interaction effect for mTORC1 and S6K1 phosphorylation. At +3h, mTORC1 and S6K1 phosphorylation was higher for placebo than for alcohol. For women, there was a significant main effect for time. mTORC1 phosphorylation was higher at +3h than at PRE and at +5h. There were no significant effects found for 4E-BP1 phosphorylation in men or women. The major findings of this study was that although RE elicited similar mTORC1 signaling both in men and in women, alcohol ingestion appeared to only attenuate RE-induced phosphorylation of the mTORC1 signaling pathway in men. The present study provides evidence that alcohol should not be ingested following RE as this ingestion could potentially hamper the desired muscular adaptations to resistance exercise by reducing anabolic signaling, at least in men.

Concepts: Cell signaling, Phosphorylation, Vastus lateralis muscle, Muscular system, Physical exercise, Weight training, Metabolism, Muscle

39

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

38

Tracy, BL and Hart, CEF. Bikram yoga training and physical fitness in healthy young adults. J Strength Cond Res 27(3): 822-830, 2013-There has been relatively little longitudinal controlled investigation of the effects of yoga on general physical fitness, despite the widespread participation in this form of exercise. The purpose of this exploratory study was to examine the effect of short-term Bikram yoga training on general physical fitness. Young healthy adults were randomized to yoga training (N = 10, 29 ± 6 years, 24 sessions in 8 weeks) or a control group (N = 11, 26 ± 7 years). Each yoga training session consisted of 90-minute standardized supervised postures performed in a heated and humidified studio. Isometric deadlift strength, handgrip strength, lower back/hamstring and shoulder flexibility, resting heart rate and blood pressure, maximal oxygen consumption (treadmill), and lean and fat mass (dual-energy x-ray absorptiometry) were measured before and after training. Yoga subjects exhibited increased deadlift strength, substantially increased lower back/hamstring flexibility, increased shoulder flexibility, and modestly decreased body fat compared with control group. There were no changes in handgrip strength, cardiovascular measures, or maximal aerobic fitness. In summary, this short-term yoga training protocol produced beneficial changes in musculoskeletal fitness that were specific to the training stimulus.

Concepts: Osteoporosis, VO2 max, Bikram Yoga, Aerobic exercise, Bodybuilding, Physical fitness, Exercise, Strength training

37

Much recent attention has been given to the compatibility of combined aerobic and anaerobic training modalities. However few of these studies have reported data related to well-trained runners, which is a potential limitation. Therefore, due to the limited evidence available for this population, the main aim was to determine which mode of concurrent strength-endurance training might be the most effective at improving running performance in highly-trained runners. Eighteen well-trained male runners (age 23.7± 1.2 yr) with a maximal oxygen consumption (VO2max) higher than 65 mL·kg·min were randomly assigned into one of the three groups: Endurance-only Group (EG; n=6), who continued their usual training, which included general strength training with Thera-band latex-free exercise bands and endurance training; Strength Group (SG; n=6) who performed combined resistance and plyometric exercises and endurance training; Endurance-Strength Group (ESG; n=6) who performed endurance-strength training with loads of 40% and endurance training.. The study comprised 12 weeks of training in which runners trained 8 times a week (6 endurance sessions and 2 strength sessions) and 5 weeks of detraining. The subjects were tested on three different occasions (counter movement jump height, hopping test average height, one-repetition-maximum, running economy, VO2max, maximal heart rate (HRmax), peak velocity, rating of perceived exertion and 3-km time trial were measured). Findings revealed significant time x group interaction effects for all almost tests (p <0.05). We can conclude that concurrent training (CT) for both SG and ESG groups led to improved maximal strength, running economy and peak velocity with no significant effects on the VO2 kinetics pattern. The SG group also seems to show improvements in 3-km time trial tests.

Concepts: Cooper test, Exercise physiology, VO2 max, Physical fitness, Exercise

36

Gottschall, JS, Mills, J, and Hastings, B. Integration core exercises elicit greater muscle activation than isolation exercises. J Strength Cond Res 27(3): 590-596, 2013-The American College of Sports Medicine and the United States Department of Health and Human Services advocate core training as a means to improve stability, reduce injury, and maintain mobility. There are countless exercises that target the primary core trunk muscles (abdominal and lumbar) with the aim of providing these benefits. However, it is unknown as to which exercises elicit the greatest activation thereby maximizing functional gains and peak performance. Thus, our purpose was to determine whether integration core exercises that require activation of the distal trunk muscles (deltoid and gluteal) elicit greater activation of primary trunk muscles in comparison with isolation core exercises that only require activation of the proximal trunk muscles. Twenty participants, 10 men and 10 women, completed 16 randomly assigned exercises (e.g., crunch, upper body extension, and hover variations). We measured muscle activity with surface electromyography of the anterior deltoid, rectus abdominus, external abdominal oblique, lumbar erector spinae, thoracic erector spinae, and gluteus maximus. Our results indicate that the activation of the abdominal and lumbar muscles was the greatest during the exercises that required deltoid and gluteal recruitment. In conclusion, when completing the core strength guidelines, an integrated routine that incorporates the activation of distal trunk musculature would be optimal in terms of maximizing strength, improving endurance, enhancing stability, reducing injury, and maintaining mobility.

Concepts: Rectus abdominis muscle, Exercise physiology, Crunch, Muscular system, Muscle contraction, Physical exercise, Muscle, Electromyography

32

Improving the process of how physical performance is enhanced is one of the main topics evaluated by physiologists. This process often involves athletes as well as non-athletic populations. The purpose of this study was to assess the chronic response to ten weeks of static stretching exercises carried out before and during a strength training program for eight exercises on eight repetition maximum (8RM) test performance, and basal serum IGF-1 levels. Thirty recreationally trained volunteers were randomly assigned into one of three training groups: 1) SBST (performed a warm-up with a static stretching protocol before each strength training session); 2) SDST (before each training set, a static stretching exercise was performed); and 3) OST (entire session was performed without any type of stretching exercise). Strength and IGF-1 levels were collected at the beginning (pre-test) and end (post-test) of the entire experimental procedure. All exercises showed a significant increase in muscle strength for the OST group. However, the results revealed a significant increase in muscle strength for only a few exercises in the SBST (LP, LE) and SDST (LP) experimental conditions. Significant statistical differences were found between SBST and SDST for all exercises in the OST experimental condition. Furthermore, IGF-1 expression showed no significant differences in intragroup analysis. However, the OST group showed higher values (p<0.05) in post-test when compared to other groups (increased significantly only in the OST experimental condition). It has been concluded that, while all groups showed an increase in muscular strength, but the strength training performed without any type of stretching exercise, regardless of if the stretching is performed prior or during the lifting session, can more effectively increase muscle strength as well as basal serum IGF-1 levels. It was concluded that strength training, with or without the use of stretching exercises, increased muscular strength in the studied groups, and can induce an increase in IGF-1 levels.

Concepts: Muscle contraction, Warming up, Strength training, Static stretching, Muscle, Exercise, Stretching, Physical exercise

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

31

The reverse fly machine is a popular exercise for strengthening the horizontal shoulder abductors including the posterior deltoid. . There seems to be little consensus as to which hand position most effectively targets the posterior deltoid despite this option on most machines. This study investigated the impact of varying one’s hand position, and consequently altering shoulder joint rotation, on muscle activity in various glenohumeral muscles during exercise on the reverse fly machine. Nineteen resistance trained men (mean age = 23.2 ± 4.3 years; height =176.9 ± 7.1 centimeters; body mass = 81.3 ± 10.5 kilograms; body mass index = 25.9 ± 2.6) were recruited from a university population to participate in the study. In a repeated measures design, subjects grasped the hand bars on the machine with either a pronated (PRO) or neutral (NEU) grip and performed dynamic horizontal abduction repetitions to muscular failure using a load equating to approximately 75% body weight. The order of performance of the hand positions was counterbalanced between participants so that approximately half of the subjects performed PRO first and the other half performed NEU first. Surface electromyography was used to record both mean and peak muscle activity of the posterior deltoid, middle deltoid, and infraspinatus. Results showed that mean EMG activity for the posterior deltoid was significantly greater in NEU compared to PRO (p = 0.046; 95% CI = 0.1 to 7.4% MVIC). Similarly, mean EMG activity of the infraspinatus also was significantly greater in NEU compared to PRO (p = 0.002; 95% CI = 3.7 to 13.6% MVIC). The results of this study show that performing exercise on the reverse fly machine with a neutral hand position significantly increases activity of the posterior deltoid and infraspinatus muscles compared to a pronated hand position.

Concepts: Body mass index, Glenohumeral joint, Mass, Rotator cuff, Muscle, Shoulder, Deltoid muscle, Electromyography

31

The squat is a closed-chain lower body exercise commonly performed by many athletes. Muscle activity has been examined during partial and parallel squats in male weightlifters, but not in male and female runners. Therefore, this study measured muscle activity with surface electromyography (EMG) during partial and parallel squats in 20 Division I collegiate cross-country runners (10 males and 10 females) in a randomized crossover design. We hypothesized the parallel squat would increase extensor muscle activitation (i.e., hamstrings and erector spinae). Furthermore, we sought to determine if changes in muscle activity were different between males and females. Participants performed 6 repetitions using their 10 repetition maximum loads for each condition during EMG testing. EMG was performed on the right rectus femoris, biceps femoris, lumbar erector spinae, and lateral head of the gastrocnemius. Rectus femoris activity (0.18±0.01 vs. 0.14±0.01 mV) and erector spinae activity (0.16±0.01 vs. 0.13±0.01 mV) were significantly higher (p<0.05) during the parallel squat than during the partial squat condition. This increase in muscle activity may be attributed to greater ranges of motion at the hip and knee joints. Biceps femoris and gastrocnemius activity were similar between conditions. No significant differences existed between males and females (squat condition x gender; p>0.05). During preliminary isokinetic testing, both male and female runners demonstrated deficient hamstrings-to-quadriceps ratios, which would not likely improve by performing parallel squats based on our EMG findings. Despite the reduced load of the parallel squat, rectus femoris and erector spinae activity were elevated. Thus, parallel squats may help runners to train muscles vital for uphill running and correct posture, while preventing injury by using lighter weights through a larger range of motion.

Concepts: Sex, Female, Male, Gender, Flexion, Extension, Knee, Electromyography