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Glyn Howatson, Raphael Brandon and Angus M. Hunter

There is a great deal of research on the responses to resistance training; however, information on the responses to strength and power training conducted by elite strength and power athletes is sparse.

Purpose:

To establish the acute and 24-h neuromuscular and kinematic responses to Olympic-style barbell strength and power exercise in elite athletes.

Methods:

Ten elite track and field athletes completed a series of 3 back-squat exercises each consisting of 4 × 5 repetitions. These were done as either strength or power sessions on separate days. Surface electromyography (sEMG), bar velocity, and knee angle were monitored throughout these exercises and maximal voluntary contraction (MVC), jump height, central activation ratio (CAR), and lactate were measured pre, post, and 24 h thereafter.

Results:

Repetition duration, impulse, and total work were greater (P < .01) during strength sessions, with mean power being greater (P < .01) after the power sessions. Lactate increased (P < .01) after strength but not power sessions. sEMG increased (P < .01) across sets for both sessions, with the strength session increasing at a faster rate (P < .01) and with greater activation (P < .01) by the end of the final set. MVC declined (P < .01) after the strength and not the power session, which remained suppressed (P < .05) 24 h later, whereas CAR and jump height remained unchanged.

Conclusion:

A greater neuromuscular and metabolic demand after the strength and not power session is evident in elite athletes, which impaired maximal-force production for up to 24 h. This is an important consideration for planning concurrent athlete training.

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Loren Z.F. Chiu, Brian K. Schilling, Andrew C. Fry and Lawrence W. Weiss

Displacement-based measurement systems are becoming increasingly popular for assessment of force expression variables during resistance exercise. Typically a linear position transducer (LPT) is attached to the barbell to measure displacement and a double differentiation technique is used to determine acceleration. Force is calculated as the product of mass and acceleration. Despite the apparent utility of these devices, validity data are scarce. To determine whether LPT can accurately estimate vertical ground reaction forces, two men and four women with moderate to extensive resistance training experience performed concentric-only (CJS) and rebound (RJS) jump squats, two sessions of each type in random order. CJS or RJS were performed with 30%, 50%, and 70% one-repetition maximum parallel back squat 5 minutes following a warm-up and again after a 10-min rest. Displacement was measured via LPT and acceleration was calculated using the finite-difference technique. Force was estimated from the weight of the lifter-barbell system and propulsion force from the lifter-barbell system. Vertical ground reaction force was directly measured with a single-component force platform. Two-way random average-measure intraclass correlations (ICC) were used to assess the reliability of obtained measures and compare the measurements obtained via each method. High reliability (ICC > 0.70) was found for all CJS variables across the load-spectrum. RJS variables also had high ICC except for time parameters for early force production. All variables were significantly (p < 0.01) related between LPT and force platform methods with no indication of systematic bias. The LPT appears to be a valid method of assessing force under these experimental conditions.

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Rich D. Johnston, Tim J. Gabbett and David G. Jenkins

Purpose:

To determine the influence the number of contact efforts during a single bout has on running intensity during game-based activities and assess relationships between physical qualities and distances covered in each game.

Methods:

Eighteen semiprofessional rugby league players (age 23.6 ± 2.8 y) competed in 3 off-side small-sided games (2 × 10-min halves) with a contact bout performed every 2 min. The rules of each game were identical except for the number of contact efforts performed in each bout. Players performed 1, 2, or 3 × 5-s wrestles in the single-, double-, and triple-contact game, respectively. The movement demands (including distance covered and intensity of exercise) in each game were monitored using global positioning system units. Bench-press and back-squat 1-repetition maximum and the 30−15 Intermittent Fitness Test (30−15IFT) assessed muscle strength and high-intensity-running ability, respectively.

Results:

There was little change in distance covered during the single-contact game (ES = −0.16 to −0.61), whereas there were larger reductions in the double- (ES = −0.52 to −0.81) and triple-contact (ES = −0.50 to −1.15) games. Significant relationships (P < .05) were observed between 30–15IFT and high-speed running during the single- (r = .72) and double- (r = .75), but not triple-contact (r = .20) game.

Conclusions:

There is little change in running intensity when only single contacts are performed each bout; however, when multiple contacts are performed, greater reductions in running intensity result. In addition, high-intensity-running ability is only associated with running performance when contact demands are low.

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Oliver Gonzalo-Skok, Julio Tous-Fajardo, Luis Suarez-Arrones, José Luis Arjol-Serrano, José Antonio Casajús and Alberto Mendez-Villanueva

Purpose:

To compare the effects of unilateral and bilateral resistance training on single-leg power output, between-limbs imbalance (BLI), bilateral deficit (BLD), change of direction (COD), and linear sprinting and jumping performance in young elite basketball players.

Methods:

Twenty-two young (U-16–U-19) male basketball players were randomly assigned either to an exclusive unilateral (UNI) (n = 11) or a bilateral (BIL) (n = 11) resistance-training group during a 6-wk period. Both groups training consisted of 3 unilateral or bilateral 90° back-squat sets. A postdetermined number of repetitions was set until power output dropped to <10% of maximum power (MP) output. In addition, both groups performed 2 sets of 5 unilateral or bilateral drop jumps and 2 sets of 5 unilateral or bilateral countermovement jumps (CMJ). Pre- and posttraining, performance was assessed by an incremental bilateral and unilateral squat-load test, a multiple-COD test (V-cut test), a 15-m-sprint test (7.5 + 7.5 m) with one 180° COD performed with both right (180° RCOD) and left (180° LCOD) legs, a 25-m-sprint test (5- and 15-m split time), and a CMJ test.

Results:

Within-group analyses showed substantial improvements in 180° RCOD, bilateral and unilateral MP, 25-m-sprint test, and CMJ in both groups. Between-groups analyses showed substantially better results in 180° LCOD, MP with right and left legs, BLI, and BLD in UNI than in BIL.

Conclusions:

Both training programs substantially improved most of the physical-fitness tests, but only UNI reduced between-limbs asymmetry and achieved greater enhancements in actions that mostly required applying force unilaterally in basketball players.

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Ewa Jówko, Jaroslaw Sacharuk, Bozena Balasinska, Jacek Wilczak, Malgorzata Charmas, Piotr Ostaszewski and Robert Charmas

Purpose:

To evaluate the effect of acute ingestion of green tea polyphenols (GTP) on blood markers of oxidative stress and muscle damage in soccer players exposed to intense exercise.

Methods:

This randomized, double-blinded study was conducted on 16 players during a general preparation period, when all athletes participated in a strength-training program focused on the development of strength endurance. After ingestion of a single dose of GTP (640 mg) or placebo, all athletes performed an intense muscle-endurance test consisting of 3 sets of 2 strength exercises (bench press, back squat) performed to exhaustion, with a load at 60% 1-repetition maximum and 1-min rests between sets. Blood samples were collected preexercise, 5 min after the muscle-endurance test, and after 24 hr of recovery. Blood plasma was analyzed for the concentrations of thiobarbituric acid–reacting substances (TBARS), uric acid (UA), total catechins, total antioxidant status (TAS), and activity of creatine kinase (CK); at the same time, erythrocytes were assayed for the activity of superoxide dismutase (SOD).

Results:

In both groups, plasma TBARS, UA, and TAS increased significantly postexercise and remained elevated after a 24-hr recovery period. SOD activity in erythrocytes did not change significantly in response to the muscle-endurance test, whereas in both groups plasma CK activity increased significantly after 24 hr of recovery. Acute intake of GTP cased a slight but significant increase in total plasma catechins. However, GTP was found not to exert a significant effect on measured parameters.

Conclusions:

Acute ingestion of GTP (640 mg) does not attenuate exercise-induced oxidative stress and muscle damage.

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Theodore Kent Kessinger, Bridget Melton, Theresa Miyashita and Greg Ryan

performed all exercises utilized in the training intervention and were free from any existing musculoskeletal disorders or history of injury, and free from anabolic steroids or illegal agents known to increase muscle size. All subjects have practiced RT for at least 3 y without interruption. Back squat

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Jozo Grgic, Filip Sabol, Sandro Venier, Ivan Mikulic, Nenad Bratkovic, Brad J. Schoenfeld, Craig Pickering, David J. Bishop, Zeljko Pedisic and Pavle Mikulic

press and back squat exercises with a load corresponding to at least 100% of their body mass. Based on a power analysis using the G*Power software (version 3; Universität Düsseldorf, Düsseldorf, Germany), with an effect size f of 0.10 for lower-body muscle endurance, alpha error of .05, statistical

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Kevin M. Carroll, Jake R. Bernards, Caleb D. Bazyler, Christopher B. Taber, Charles A. Stuart, Brad H. DeWeese, Kimitake Sato and Michael H. Stone

repetitions; RM, repetition maximum; VJ, vertical jump. a Symbolizes downset at 60% of working weight (RI SR only). Table 2 Training Exercises for All Subjects Training block Day 1 Day 2 Day 3 Strength endurance Back squat, overhead press, bench press, DB triceps extension CG MTP, CG SLDL, BB bent row, DB

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INTERNATIONAL SPORT COACHING JOURNAL

DIGEST VOLUME 6, ISSUE #1

is given to the coaching behaviours (e.g., feedback) that could enhance performance and training adaptations. The aim of this study was to compare the differences in barbell velocity during the back squat following verbal kinematic feedback and visual kinematic feedback, and verbal encouragement

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Hong-Wen Wu, Cheng-Feng Tsai, Kai-Han Liang and Yi-Wen Chang

. Aspe and Swinton 20 indicated that the overhead squat demonstrated higher activation in anterior trunk muscles, whereas the back squat demonstrated higher activation in posterior trunk muscles. Contreras et al 21 measured the EMG of gluteus maximus, gluteus medius, biceps femoris, and vastus