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.
Samuel Ryan, Emidio Pacecca, Jye Tebble, Joel Hocking, Thomas Kempton and Aaron J. Coutts
Purpose: To examine the measurement reliability and sensitivity of common athlete monitoring tools in professional Australian Football players. Methods: Test–retest reliability (noise) and weekly variation (signal) data were collected from 42 professional Australian footballers from 1 club during a competition season. Perceptual wellness was measured via questionnaires completed before main training sessions (48, 72, and 96 h postmatch), with players providing a rating (1–5 Likert scale) regarding their muscle soreness, sleep quality, fatigue level, stress, and motivation. Eccentric hamstring force and countermovement jumps were assessed via proprietary systems once per week. Heart rate recovery was assessed via a standard submaximal run test on a grass-covered field with players wearing a heart rate monitor. The heart rate recovery was calculated by subtracting average heart rate during final 10 seconds of rest from average heart rate during final 30 seconds of exercise. Typical test error was reported as coefficient of variation percentage (CV%) and intraclass coefficients. Sensitivity was calculated by dividing weekly CV% by test CV% to produce a signal to noise ratio. Results: All measures displayed acceptable sensitivity. Signal to noise ratio ranged from 1.3 to 11.1. Intraclass coefficients ranged from .30 to .97 for all measures. Conclusions: The heart rate recovery test, countermovement jump test, eccentric hamstring force test, and perceptual wellness all possess acceptable measurement sensitivity. Signal to noise ratio analysis is a novel method of assessing measurement characteristics of monitoring tools. These data can be used by coaches and scientists to identify meaningful changes in common measures of fitness and fatigue in professional Australian football.
Robert MacKenzie, Linda Monaghan, Robert A. Masson, Alice K. Werner, Tansinee S. Caprez, Lynsey Johnston and Ole J. Kemi
Purpose: Rock climbing performance relies on many characteristics. Herein, the authors identified the physical and physiological determinants of peak performance in rock climbing across the range from lower grade to elite. Methods: Forty four male and 33 female climbers with onsight maximal climbing grades 5a–8a and 5a–7b+, respectively, were tested for physical, physiological, and psychological characteristics (independent variables) that were correlated and modeled by multiple regression and principal component analysis to identify the determinants of rock climbing ability. Results: In males, 23 of 47 variables correlated with climbing ability (P < .05, Pearson correlation coefficients .773–.340), including shoulder endurance, hand and finger strength, shoulder power endurance, hip flexibility, lower-arm grip strength, shoulder power, upper-arm strength, core-body endurance, upper-body aerobic endurance, hamstrings and lower-back flexibility, aerobic endurance, and open-hand finger strength. In females, 10 of 47 variables correlated with climbing ability (P < .05, Pearson correlation coefficients .742–.482): shoulder endurance and power, lower-arm grip strength, balance, aerobic endurance, and arm span. Principal component analysis and univariate multiple regression identified the main explanatory variables. In both sexes, shoulder power and endurance measured as maximum pull-ups, average arm crank power, and bent-arm hang, emerged as the main determinants (P < .01; adjusted R 2 = .77 in males and .62 in females). In males, finger pincer (P = .07) and grip strength also had trends (P = .09) toward significant effects. Finally, in test-of-principle training studies, they trained to increase main determinants 42% to 67%; this improved climbing ability 2 to 3 grades. Conclusions: Shoulder power and endurance majorly determines maximal climbing. Finger, hand, and arm strength, core-body endurance, aerobic endurance, flexibility, and balance are important secondary determinants.
Kristof Kipp, John Krzyszkowski and Daniel Kant-Hull
Purpose: To use an artificial neural network (ANN) to model the effect of 15 weeks of resistance training on changes in countermovement jump (CMJ) performance in male track-and-field athletes. Methods: Resistance training volume load (VL) of 21 male division I track-and-field athletes was monitored over the course of 15 weeks, which covered their indoor and outdoor competitive season. Weekly CMJ height was also measured and used to calculate the overall 15-week change in CMJ performance. A feed-forward ANN with 5 hidden layers was used to model how the VL from each of the 15 weeks was associated with the overall change in CMJ height. Results: Testing the performance of the developed ANN on 4 separate athletes showed that 15 weeks of VL data could predict individual changes in CMJ height with an average error between 0.21 and 1.47 cm, which suggested that the ANN adequately modeled the relationship between weekly VL and its effects on CMJ performance. In addition, analysis of the relative importance of each week in predicting changes in CMJ height indicated that the VLs during deload or taper weeks were the best predictors (10%–17%) of changes in CMJ performance. Conclusions: ANN can be used to effectively model the effects of weekly VL on changes in CMJ performance. In addition, ANN can be used to assess the relative importance of each week in predicting changes in CMJ height.
Bryan L. Riemann and George J. Davies
Context: Previous investigations have examined the reliability, normalization, and underlying projection mechanics of the seated single-arm shot-put (SSASP) test. Although the test is believed to reflect test limb strength, there have been no assessments determining whether test performance is directly associated with upper-extremity strength. Objective: To determine the relationship between isokinetic pushing force and SSASP performance and conduct a method comparison analysis of limb symmetry indices between the 2 tests. Design: Controlled laboratory study. Setting: Biomechanics laboratory. Patients (or Other Participants): Twenty-four healthy and physically active men (n = 12) and women (n = 12). Intervention(s): Participants completed the SSASP and isokinetic pushing tests using their dominant and nondominant arms. Main Outcome Measures: SSASP distance and isokinetic peak force. Results: Significant moderate to strong relationships were revealed between the SSASP distances and isokinetic peak forces for both limbs. The Bland–Altman analysis results demonstrated significantly (P < .002) greater limb symmetry indices for the SSASP (both medicine balls) than the isokinetic ratios, with biases ranging from −0.094 to −0.159. The limits of agreement results yielded intervals ranging from ±0.241 to ±0.340 and ±0.202 to ±0.221 from the biases. Conclusions: These results support the notion that the SSASP test reflects upper-extremity strength. The incongruency of the limb symmetry indices between the 2 tests is likely reflective of the differences in the movement patterns and coordination requirements of the 2 tests.
Robert J. Brychta, Vaka Rögnvaldsdóttir, Sigríður L. Guðmundsdóttir, Rúna Stefánsdóttir, Soffia M. Hrafnkelsdóttir, Sunna Gestsdóttir, Sigurbjörn A. Arngrímsson, Kong Y. Chen and Erlingur Jóhannsson
Introduction: Sleep is often quantified using self-report or actigraphy. Self-report is practical and less technically challenging, but prone to bias. We sought to determine whether these methods have comparable sensitivity to measure longitudinal changes in adolescent bedtimes. Methods: We measured one week of free-living sleep with wrist actigraphy and usual bedtime on school nights and non-school nights with self-report questionnaire in 144 students at 15 y and 17 y. Results: Self-reported and actigraphy-measured bedtimes were correlated with one another at 15 y and 17 y (p < .001), but reported bedtime was consistently earlier (>30 minutes, p < .001) and with wide inter-method confidence intervals (> ±106 minutes). Mean inter-method discrepancy did not differ on school nights at 15 y and 17 y but was greater at 17 y on non-school nights (p = .002). Inter-method discrepancy at 15 y was not correlated to that at 17 y. Mean change in self-reported school night bedtime from 15 y to 17 y did not differ from that by actigraphy, but self-reported bedtime changed less on non-school nights (p = .002). Two-year changes in self-reported bedtime did not correlate with changes measured by actigraphy. Conclusions: Although methods were correlated, consistently earlier self-reported bedtime suggests report-bias. More varied non-school night bedtimes challenge the accuracy of self-report and actigraphy, reducing sensitivity to change. On school nights, the methods did not differ in group-level sensitivity to changes in bedtime. However, lack of correlation between bedtime changes by each method suggests sensitivity to individual-level change was different. Methodological differences in sensitivity to individual- and group-level change should be considered in longitudinal studies of adolescent sleep patterns.
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.