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.
You are looking at 1 - 10 of 24,770 items
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.
Carl Foster, Jos J. de Koning, Christian Thiel, Bram Versteeg, Daniel A. Boullosa, Daniel Bok and John P. Porcari
Background: Pacing studies suggest the distribution of effort for optimizing performance. Cross-sectional studies of 1-mile world records (WRs) suggest that WR progression includes a smaller coefficient of variation of velocity. Purpose: This study evaluates whether intraindividual pacing used by elite runners to break their own WR (1 mile, 5 km, and 10 km) is related to the evolution of pacing strategy. We provide supportive data from analysis in subelite runners. Methods: Men’s WR performances (with 400-m or 1-km splits) in 1 mile, 5 km, and 10 km were retrieved from the IAAF database (from 1924 to present). Data were analyzed relative to pacing pattern when a runner improved their own WR. Similar analyses are presented for 10-km performance in subelite runners before and after intensified training. Results: WR performance was improved in 1 mile (mean [SD]: 3:59.4 [11.2] to 3:57.2 [8.6]), 5 km (13:27 [0:33] to 13:21 [0:33]), and 10 km (28:35 [1:27] to 28:21 [1:21]). The average coefficient of variation did not change in the 1 mile (3.4% [1.8%] to 3.6% [1.6%]), 5 km (2.4% [0.9%] to 2.2% [0.8%]), or 10 km (1.4% [0.1%] to 1.5% [0.6%]) with improved WR. When velocity was normalized to the percentage mean velocity for each race, the pacing pattern was almost identical. Very similar patterns were observed in subelite runners in the 10 km. When time improved from 49:20 (5:30) to 45:56 (4:58), normalized velocity was similar, terminal RPE increased (8.4 [1.6] to 9.1 [0.8]), coefficient of variation was unchanged (4.4% [1.1%] to 4.8% [2.1%]), and VO2max increased (49.8 [7.4] to 55.3 [8.8] mL·min−1·kg−1). Conclusion: The results suggest that when runners break their own best performances, they employ the same pacing pattern, which is different from when WRs are improved in cross-sectional data.
Irineu Loturco, Timothy Suchomel, Chris Bishop, Ronaldo Kobal, Lucas A. Pereira and Michael R. McGuigan
Purpose: To identify the bar velocities that optimize power output in the barbell hip thrust exercise. Methods: A total of 40 athletes from 2 sports disciplines (30 track-and-field sprinters and jumpers and 10 rugby union players) participated in this study. Maximum bar-power outputs and their respective bar velocities were assessed in the barbell hip thrust exercise. Athletes were divided, using a median split analysis, into 2 groups according to their bar-power outputs in the barbell hip thrust exercise (“higher” and “lower” power groups). The magnitude-based inferences method was used to analyze the differences between groups in the power and velocity outcomes. To assess the precision of the bar velocities for determining the maximum power values, the coefficient of variation (CV%) was also calculated. Results: Athletes achieved the maximum power outputs at a mean velocity, mean propulsive velocity, and peak velocity of 0.92 (0.04) m·s−1 (CV: 4.1%), 1.02 (0.05) m·s−1 (CV: 4.4%), and 1.72 (0.14) m·s−1 (CV: 8.4%), respectively. No meaningful differences were observed in the optimum bar velocities between higher and lower power groups. Conclusions: Independent of the athletes’ power output and bar-velocity variable, the optimum power loads frequently occur at very close bar velocities.
Miguel A. Sanchez-Lastra, Vicente de Dios Álvarez and Carlos Ayán Pérez
Background: The promotion of physical activity among imprisoned people is a public health strategy that could help to improve the health status of this collective. This systematic review is aimed at reviewing the scientific evidence regarding the effects of exercise training programs performed by inmates. Methods: A systematic search for randomized controlled trials aimed at identifying the characteristics and effects of prison-based exercise training programs on imprisoned people was carried through MEDLINE, SPORTDiscus, and Scopus. Results: A total of 11 randomized controlled studies were selected, and the methodological quality of these was acceptable according to the Downs and Black scale. The proposed interventions were mainly based on the performance of aerobic or combined exercise training programs. Generally, the participants were healthy men who were imprisoned for at least 2 months and up to 15 years. Ten out of the 11 studies reported significant changes on physical and mental health–related variables, after the intervention took place. Conclusion: These findings suggest that prison-based exercise programs constitute a feasible and useful strategy for improving the physical and mental health status of prisoners.
Antonio Dello Iacono, Marco Beato and Israel Halperin
Purpose: To compare the effects of 2 postactivation potentiation (PAP) protocols using traditional-set or cluster-set configurations on countermovement jump performance. Methods: Twenty-six male basketball players completed 3 testing sessions separated by 72 hours. On the first session, subjects performed barbell jump squats with progressively heavier loads to determine their individual optimum power load. On the second and third sessions, subjects completed 2 PAP protocols in a randomized order: 3 sets of 6 repetitions of jump squats using optimum power load performed with either a traditional-set (no interrepetition rest) or a cluster-set (20-s rest every 2 repetitions) configuration. After a warm-up, countermovement jump height was measured using a force platform before, 30 seconds, 4 minutes, and 8 minutes after completing the PAP protocols. The following kinetic variables were also analyzed and compared: relative impulse, ground reaction force, eccentric displacement, and vertical leg-spring stiffness. Results: Across both conditions, subjects jumped lower at post 30 seconds by 1.21 cm, and higher in post 4 minutes by 2.21 cm, and in post 8 minutes by 2.60 cm compared with baseline. However, subjects jumped higher in the cluster condition by 0.71 cm (95% confidence interval, 0.37 to 1.05 cm) in post 30 seconds, 1.33 cm (95% confidence interval, 1.02 to 1.65 cm) in post 4 minute, and 1.64 cm (95% confidence interval, 1.41 to 1.88 cm) in post 8 minutes. The superior countermovement jump performance was associated with enhanced kinetic data. Conclusions: Both protocols induced PAP responses in vertical jump performance using jump squats at optimum power load. However, the cluster-set configuration led to superior performance across all time points, likely due to reduced muscular fatigue.
Anna M. Ifarraguerri, Danielle M. Torp, Abbey C. Thomas and Luke Donovan
Individuals with chronic ankle instability (CAI) have been shown to have increased lateral plantar pressure during walking which is thought to contribute to symptoms associated with CAI. The objective of this study was to determine whether real-time video feedback can reduce lateral plantar pressure in individuals with CAI. Twenty-six participants with CAI completed 30 s of treadmill walking while plantar pressure was measured using an in-shoe plantar pressure system (baseline). Next, participants completed an additional 30 s of treadmill walking while receiving video feedback (VID FB). During the VID FB condition, participants had a significant decrease in medial forefoot peak pressure and medial midfoot pressure-time integral; however, both changes were associated with small effect sizes. Real-time video feedback did not reduce lateral plantar pressure in individuals with CAI; therefore, other gait retraining strategies should be considered when treating patients with CAI.
Rebecca Quinlan and Jessica A. Hill
Purpose: To investigate the effects of supplementation with tart cherry juice (TCJ) on markers of recovery after intermittent exercise under habitual dietary conditions. Methods: Using a randomized, single-blind, placebo (PLA)-controlled, independent-groups design, 20 team-sport players (8 male and 12 female; age 26  y, height 175.4 [9.6] cm, body mass 70.2 [12.6] kg) were divided equally into 2 groups and consumed either TCJ or PLA twice per day for 8 consecutive days while following their normal dietary habits. Participants completed an adapted version of the Loughborough Intermittent Shuttle Test (LIST) on day 6 of supplementation. Countermovement jump, 20-m sprint, maximal voluntary isometric contraction, and delayed onset muscle soreness were assessed at baseline and 1, 24, and 48 hours post-LIST. Blood markers of muscle damage (creatine kinase) and inflammation (C-reactive protein) were taken presupplementation, immediately pre-LIST, and 1, 24, and 48 hours post-LIST. Data were analyzed using a repeated-measures analysis of variance. Results: Countermovement jump, 20-m sprint, and maximal voluntary isometric contraction showed significantly faster recovery with TCJ (P < .05) at 24 and 48 hours post-LIST. A significant interaction effect (P < .05) was observed for muscle soreness; however, Bonferroni post hoc analysis could not identify when the significant differences between TCJ and PLA occurred. There were no significant differences throughout recovery between TCJ and PLA for C-reactive protein and creatine kinase (P < .05). Conclusion: The results suggest that TCJ, in addition to habitual diet, can accelerate recovery after intermittent exercise and therefore extend the efficacy of TCJ in accelerating recovery in team sports.
Andrés Pérez, Domingo J. Ramos-Campo, Cristian Marín-Pagan, Francisco J. Martínez-Noguera, Linda H. Chung and Pedro E. Alcaraz
Purpose: To compare the effects of 2 different intensity distribution training programs (threshold [THR] and polarized [POL]) on fat metabolism and neuromuscular variables. Methods: Twenty ultrarunners were allocated to POL (n = 11; age 40.6 [9.7] y, weight 73.5 [10.8] kg, VO2max 55.8 [4.9] mL·kg−1·min−1) or THR group (n = 9; age 36.8 [9.2] y, weight 75.5 [10.4] kg, VO2max 57.1 [5.2] mL·kg−1·min−1) and performed a 12-week training program that consisted of 5 running sessions, 2 strength sessions, and 1 day of full rest per week. Both groups performed similar total training duration and load but with different intensity distribution during running sessions. Resting metabolic rate, fat metabolism, isometric rate of force development (RFD; N·s−1) and maximal voluntary contraction in the knee extensor, and electromyographic amplitude were measured before and after each program. Results: A significant decrease in RFD0–100 ms (Δ −13.4%; P ≤ .001; effect size [ES] = 1.00), RFD0–200 ms (Δ −11.7%; P ≤ .001; ES = 1.4), and RFDpeak (Δ −18%; P ≤ .001; ES = 1.4) were observed in the POL group. In THR group, a significant increase in mean electromyographic amplitude (Δ 24.4%; P = .02; ES = 1.4) was observed. There were no significant differences between groups in any of the variables. Conclusions: Similar adaptations in fat metabolism and neuromuscular performance can be achieved after 12 weeks of POL or THR intensity distribution. However, THR distribution appears to better maintain strength (RFD) and improve mean electromyographic amplitude. Nevertheless, the combination of both running and maximum strength training could influence on results because of the residual fatigue thus inducing suboptimal adaptations in the POL group.