Sixteen men completed four trials at random as follows: (Trial A) performance of a single bout of resistance exercise preceded by placebo ingestion (vitamin C); (Trial B) ingestion of 1,500 mg L-arginine and 1,500 mg L-lysine, immediately followed by exercise as in Trial A; (Trial C) ingestion of amino acids as in Trial B and no exercise; (Trial D) placebo ingestion and no exercise. Growth hormone (GH) concentrations were higher at 30,60, and 90 min during the exercise trials (A and B) compared with the resting trials (C and D) (p < .05). No differences were noted in [GH] between the exercise trials. [GH] was significantly elevated during resting conditions 60 min after amino acid ingestion compared with the placebo trial. It was concluded that ingestion of 1,500 mg arginine and 1,500 mg ly sine immediately before resistance exercise does not alter exercise-induced changes in [GH] in young men. However, when the same amino acid mixture is ingested under basal conditions, the acute secretion of GH is increased.
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Richard R. Suminski, Robert J. Robertson, Fredric L. Goss, Silva Arslanian, Jie Kang, Sergio DaSilva, Alan C. Utter and Kenneth F. Metz
Ben D. Kern, Kim C. Graber, Amelia Mays Woods and Tom Templin
Physical education teachers have been criticized for not implementing progressive or innovative instruction resulting in enhanced student knowledge and skills for lifetime participation in physical activity. Purpose: To investigate how teachers with varying dispositions toward change perceive socializing agents and teaching context as barriers to or facilitators of making pedagogical change. Methods: Thirty-two teachers completed a survey of personal dispositions toward change and participated in in-depth interviews. Results: Teachers perceived that students’ response to instructional methods and student contact time (days/week), as well as interactions with teaching colleagues and administrators influenced their ability to make pedagogical changes. Teachers with limited student contact time reported scheduling as a barrier to change, whereas daily student contact was a facilitator. Change-disposed teachers were more likely to promote student learning and assume leadership roles. Conclusion: Reform efforts should include consideration of teacher dispositions and student contact time.
Peter J. Whalley, Chey G. Dearing and Carl D. Paton
Purpose: Caffeine is frequently used by athletes as an ergogenic aid. Various alternate forms of caffeine administration are available, which may produce different effects. This investigation compares the effects of different forms of caffeine supplementation on 5-km running performance, and the relationship between athlete ability and degree of enhancement attained. Methods: Fourteen amateur runners completed a series of self-paced outdoor time trials following unknown ingestion of a placebo (P) or one of 3 alternate forms of caffeine supplement. Trials were randomized in a crossover design with caffeine (approximately 3–4.5 mg·kg−1) administered 15 minutes before each trial via chewing gum (CG), dissolvable mouth strips (CS), or tablet (CT). Results: Compared with P, all caffeine supplements led to worthwhile enhancements in running performance with a mean (±95% confidence limit) overall effect across all supplements of 1.4% ± 0.9%. Individual caffeine treatment effects (CG = 0.9% ± 1.4%, CS = 1.2% ± 1.0%, and CT = 2.0% ± 1.1%) were not significantly different (P > .05) from each other; however, CT trials produced the largest gain and was significantly different (P = .02) compared with P. There was no significant difference in heart rate or rate of perceived exertion across the performance trials. The magnitude of caffeine enhancement was also strongly correlated (r = .87) with no-treatment performance time. Conclusions: The findings showed that irrespective of delivery form, moderate dose of caffeine supplementation produces worthwhile gains in 5-km running performance compared with a P. Furthermore, the magnitude of caffeine enhancement is highly individualized, but it appears related to athlete performance ability.
Manuel Terraza-Rebollo and Ernest Baiget
Purpose: To examine the postactivation potentiation effect on serve velocity and accuracy in young competition tennis players using complex training, and comparing different upper and lower body heavy-load resistance exercises (HLRE). Methods: Fifteen competition tennis players (9 boys and 6 girls; age 15.6 [1.5] y) performed 1 control session and 3 experimental sessions using HLRE in a crossover randomized design: (1) bench press, (2) half squat, (3) bench press plus half squat, and (4) control trial. HLRE were performed by accomplishing 3 sets of 3 repetitions when bench press or half squat conditions were performed and 2 sets of 3 repetitions of each exercise when bench press plus half squat condition was performed at 80% 1-repetition maximum, lifting the load at maximum speed. To assess the serve velocity and accuracy, all participants performed 32 flat serves after the HLRE, divided into 4 sets of 8 serves (0, 5, 10, and 15 min postexercise), resting 20 seconds between serves, and 2 minutes and 40 seconds between sets. Results: There were no significant (P > .05) differences in ball velocity and accuracy following each recovery time and exercise, compared with the basal situation. Conclusions: These results suggest that complex training using HLRE is not a useful method for eliciting the postactivation potentiation effect in tennis serve and does not have any effect in serve accuracy in young competition tennis players.
Jeffrey D. Simpson, Ludmila Cosio-Lima, Eric M. Scudamore, Eric K. O’Neal, Ethan M. Stewart, Brandon L. Miller, Harish Chander and Adam C. Knight
Purpose: Wearing a weighted vest (WV) during daily living and training can enhance jump and sprint performance; however, studies examining the efficacy of this method in female populations is limited. This study examined the effect of wearing a WV during daily living and training on countermovement jump (CMJ), change-of-direction, and sprint performance. Methods: Trained females were separated into intervention (n = 9) and control (n = 10) groups. The intervention group wore WVs of ∼8% body mass 4 days per week for 8 hours per day (32 h/wk total), and 3 training sessions per week for the first 3 weeks. Subsequently, 3 weeks of regular training without WV stimulus was completed. The control group received no intervention and continued normal training for 6 weeks. Average and best performance was assessed on the single CMJ, four continuous CMJ, t-test change-of-direction drill, and a 25-m sprint at baseline, week 3, and week 6. Results: No significant interactions or group effects were found. However, significant time main effects revealed increases in average rate of force development during the CMJ from baseline to week 3 (P = .048) and week 6 (P = .013), whereas peak vertical ground reaction force increased during the four continuous CMJ from baseline to week 3 (P = .048) and week 6 (P = .025) for both groups. Conclusions: The lower relative WV load used in this study failed to elicit significant improvements in jump and sprint performance in comparison with routine training, or that which have been found in past investigations with elite male athletes completing high-intensity performance tasks with greater WV loads.
Francesco Campa, Catarina N. Matias, Elisabetta Marini, Steven B. Heymsfield, Stefania Toselli, Luís B. Sardinha and Analiza M. Silva
Purpose: To analyze the association between body fluid changes evaluated by bioelectrical impedance vector analysis and dilution techniques over a competitive season in athletes. Methods: A total of 58 athletes of both sexes (men: age 18.7 [4.0] y and women: age 19.2 [6.0] y) engaging in different sports were evaluated at the beginning (pre) and 6 months after (post) the competitive season. Deuterium dilution and bromide dilution were used as the criterion methods to assess total body water (TBW) and extracellular water (ECW), respectively; intracellular water (ICW) was calculated as TBW–ECW. Bioelectrical resistance and reactance were obtained with a phase-sensitive 50-kHz bioelectrical impedance analysis device; bioelectrical impedance vector analysis was applied. Dual-energy X-ray absorptiometry was used to assess fat mass and fat-free mass. The athletes were empirically classified considering TBW change (pre–post, increase or decrease) according to sex. Results: Significant mean vector displacements in the postgroups were observed in both sexes. Specifically, reductions in vector length (Z/H) were associated with increases in TBW and ICW (r = −.718, P < .01; r = −.630, P < .01, respectively) and decreases in ECW:ICW ratio (r = .344, P < .05), even after adjusting for age, height, and sex. Phase-angle variations were positively associated with TBW and ICW (r = .458, P < .01; r = .564, P < .01, respectively) and negatively associated with ECW:ICW (r = −.436, P < .01). Phase angle significantly increased in all the postgroups except in women in whom TBW decreased. Conclusions: The results suggest that bioelectrical impedance vector analysis is a suitable method to obtain a qualitative indication of body fluid changes during a competitive season in athletes.
Christian P. Cheung, Joshua T. Slysz and Jamie F. Burr
Purpose: Ischemic preconditioning (IPC) through purposeful circulatory occlusion may enhance exercise performance. The value of IPC for improving performance is controversial owing to challenges with employing effective placebo controls. This study examines the efficacy of IPC versus a deceptive sham protocol for improving performance to determine whether benefits of IPC are attributable to true physiological effects. It was hypothesized that IPC would favorably alter performance more than a sham treatment and that physiological responses to exercise would be affected only after IPC treatment. Methods: In a randomized order, 16 participants performed incremental exercise to exhaustion on a cycle ergometer in control conditions and after sham and IPC treatments. Participants rated their belief as to the efficacy of each treatment compared with control. Results: Time to exhaustion was greatest after IPC (control = 1331  s, IPC = 1429  s, sham = 1343  s, P = .02), despite negative performance expectations after IPC and positive expectation after sham. Maximal aerobic power remained unchanged after both SHAM and IPC (control = 42.0 [5.2], IPC = 41.7 [5.5], sham = 41.6 [5.5] mL·kg−1·min−1, P = .7), as did submaximal lactate concentration (control = 8.9 [2.6], sham = 8.0 [1.9], IPC = 7.7 [2.1] mmol, P = .1) and oxygen uptake (control = 37.8 [4.8], sham = 37.5 [5.3], IPC = 37.5 [5.5] mL·kg−1·min−1, P = .6). Conclusions: IPC before cycling exercise provides an ergogenic benefit that is not attributable to a placebo effect from positive expectation and that was not explained by traditionally suggested mechanisms.
Antonio Dello Iacono, Stephanie Valentin, Mark Sanderson and Israel Halperin
Purpose: To investigate the test–retest reliability and criterion validity of the isometric horizontal push test (IHPT), a newly designed test that selectively measures the horizontal component of maximal isometric force. Methods: Twenty-four active males with ≥3 years of resistance training experience performed 2 testing sessions of the IHPT, separated by 3 to 4 days of rest. In each session, subjects performed 3 maximal trials of the IHPT with 3 minutes of rest between them. The peak force outputs were collected simultaneously using a strain gauge and the criterion equipment consisting of a floor-embedded force plate. Results: The test–retest reliability of peak force values was nearly perfect (intraclass correlation coefficient = ∼.99). Bland–Altman analysis showed excellent agreement between days with nearly no bias for strain gauge 1.2 N (95% confidence interval [CI], −3 to 6 N) and force plate 0.8 N (95% CI, −4 to 6 N). A nearly perfect correlation was observed between the strain gauge and force plate (r = .98, P < .001), with a small bias of 8 N (95% CI, 1.2 to 15 N) in favor of the force plate. The sensitivity of the IHPT was also good, with smallest worthwhile change greater than standard error of measurement for both the strain gauge (smallest worthwhile change: 29 N; standard error of measurement: 17 N; 95% CI, 14 to 20 N) and the force plate (smallest worthwhile change: 29 N; standard error of measurement: 18 N; 95% CI, 14 to 19 N) devices. Conclusions: The high degree of validity, reliability, and sensitivity of the IHPT, coupled with its affordability, portability, ease of use, and time efficacy, point to the potential of the test for assessment and monitoring purposes.
Borja Muniz-Pardos, Alejandro Gómez-Bruton, Ángel Matute-Llorente, Alex González-Agüero, Alba Gómez-Cabello, José A. Casajús and Germán Vicente-Rodríguez
Purpose: To examine the effects of a 6-month whole-body vibration (WBV) training on lower-body strength (LBS), lower-body power (LBP), and swimming performance in adolescent trained swimmers. Methods: Thirty-seven swimmers (23 males and 14 females; 14.8 [1.3] y) were randomly assigned to the WBV (n = 20) or the control group (n = 17). Isometric LBS (knee extension and half squat) and LBP (vertical and horizontal jumps and 30-m sprint) tests were performed before and after the intervention period. Swimming performance times in 100 m were collected from official competitions. As time × sex interaction was not found for any variable (P > .05), males and females were analyzed as a whole. Results: Within-group analyses showed a most likely beneficial moderate effect of WBV on isometric knee extension (effect size [ES] = 0.63), 30-m sprint test (ES = 0.62), and 100-m performance (ES = 0.25), although these were corresponded with comparable small to moderate effects in the control group (ES = 0.73, 0.71, and 0.20, respectively). The control group obtained a small possibly beneficial effect of swimming-only training on vertical jump performance, whereas no effect was observed in the WBV group. Unclear effects were observed for the rest of the variables assessed. Between-group analyses revealed unclear effects of WBV training when compared with the control condition in all studied variables. Conclusions: There is no current evidence to support the use of WBV training, and therefore, coaches and sports specialists should select other methods of training when the aim is to increase LBS, LBP, or swimming performance.