RESUMEN
This study investigated the influences of player number and playing area size on the heart rate (HR) responses elicited by junior male rugby league players during small-sided games (SSGs). Twenty-two players from a professional club (n = 22, mean age: 14.5 +/- 1.5 years; stature: 172.5 +/- 11.4 cm; body mass: 67.8 +/- 15.1 kg; Vo2peak: 53.3 +/- 5.6 mL.kg.min; HRmax: 198 +/- 7.8 beats.min) participated in 2 repeated trials of six 4-minute conditioned SSGs over a 2-week period. The SSGs varied by playing area size-15 x 25 m, 20 x 30 m, and 25 x 35 m-and player number-4v4 and 6v6. HRs were recorded continuously in each game and expressed as overall and age-related (15-16 and 12-13 years) means and percent of maximum (%HRmax). Analysis revealed nonsignificant (p > 0.05) effects of trials and playing area size on HRs but a significant effect of player number in the 15-16 age group only (p < 0.001), with HRs being higher in the 4v4 (90.6% HRmax) than the 6v6 SSGs (86.2% HRmax). The HR responses were found to be repeatable in all SSG conditions (within +/- 1.9% HRmax), apart from the small 6v6 condition in the older players. The findings demonstrate that these SSGs generate physiological responses suitable for aerobic conditioning that, although unaffected by the size of the area used, are sensitive to the player number. Accordingly, among such players it is advisable that coaches use 4v4 SSGs to achieve an appropriate and consistent aerobic conditioning stimulus.
Asunto(s)
Rendimiento Atlético , Fútbol Americano/fisiología , Frecuencia Cardíaca/fisiología , Consumo de Oxígeno/fisiología , Aptitud Física/fisiología , Adolescente , Análisis de Varianza , Antropometría , Composición Corporal , Regulación de la Temperatura Corporal/fisiología , Estudios de Cohortes , Humanos , Masculino , Educación y Entrenamiento Físico/métodos , Resistencia Física/fisiología , Probabilidad , Reproducibilidad de los Resultados , Análisis y Desempeño de TareasRESUMEN
PURPOSE: To investigate the effect of ingesting a carbohydrate-electrolyte solution (CHO-E), in subjects with reduced carbohydrate stores, during an intermittent shuttle running test (LIST) on soccer passing (LSPT) and shooting (LSST) performance. METHODS: Sixteen healthy male university soccer players ingested either a 6.4% CHO-E or placebo (PLA) solution during 90 min of the LIST (5 mL x kg(-1) BM before and 2 mL x kg(-1) BM every 15 min of exercise), in a double-blind, randomized, crossover design, with each trial separated by at least 7 d. On the evening before the main trial (17:00 h), subjects performed the glycogen-reducing cycling exercise (approximately 80 min at 70% VO2max). They were then fed a low-carbohydrate evening meal and reported to the laboratory the following morning after a 10-h fast. Blood was collected at rest and after every 30 min of exercise; skill tests were performed before and after the LIST. RESULTS: The change in mean LSST performance from pre- to post-LIST was better in the CHO-E trial (11 +/- 45 vs -16 +/- 42%; P < 0.01) but not significantly different for the LSPT performance (-1 +/- 10% (CHO-E) vs -6 +/- 13% (PLA), P = 0.13). Sprint performance during the LIST was quicker in the CHO-E trial (2.50 +/- 0.13 vs 2.53 +/- 0.13 s, P < 0.01). Plasma glucose was higher in the CHO-E trial after 90 min of exercise (5.2 +/- 0.3 vs 3.9 +/- 0.4 mM, P < 0.01). CONCLUSIONS: Ingestion of a carbohydrate-electrolyte solution during exercise enabled subjects with compromised glycogen stores to better maintain skill and sprint performance than when ingesting fluid alone.
Asunto(s)
Carbohidratos de la Dieta/administración & dosificación , Electrólitos/administración & dosificación , Fútbol , Análisis y Desempeño de Tareas , Adolescente , Adulto , Método Doble Ciego , Inglaterra , Humanos , Masculino , Oxígeno/metabolismo , PlacebosRESUMEN
PURPOSE: This study examined the effect of variable-intensity shuttle running on gastric emptying of a carbohydrate-free placebo (Plac) drink and of a 6.4% carbohydrate-electrolyte (CHO) sports drink. METHOD: We compared the volume of test drink emptied during two 15-min periods of walking exercise (WE) with that during two 15-min periods of the Loughborough Intermittent Shuttle Test (LIST). Gastric emptying was measured on the four trials using a double-sampling aspiration technique in eight healthy males after ingestion of a 420 +/- 49 mL and a 168 +/- 20 mL bolus of the appropriate test drink at the start of the first and second exercise period, respectively. RESULTS: During the initial 15 min of exercise, the mean (+/-SD) volume of Plac (124 +/- 95 mL) and CHO (71 +/- 43 mL) drink emptied was similar between the two LIST trials, but the volume of Plac (227 +/- 85 mL) and CHO (159 +/- 63 mL) drinks emptied on the WE trials was greater than for the respective test drinks on the LIST trials. Similar volumes of test drinks were emptied on all trials (P = 0.20) during the second 15 min of exercise. Over the 30 min of each trial, the exercise intensity of the LIST reduced the volume of the Plac (211 +/- 108 mL) and CHO (208 +/- 83 mL) drink emptied compared with that on the WE trial for the Plac (396 +/- 74 mL) and CHO (293 +/- 73 mL) drink, respectively. CONCLUSIONS: The exercise intensity of the LIST is sufficient to slow gastric emptying of carbohydrate and noncarbohydrate containing drinks compared with walking. Dilute carbohydrate-electrolyte drinks empty at about the same rate as carbohydrate-free beverages during variable-intensity running.
Asunto(s)
Bebidas , Vaciamiento Gástrico/fisiología , Carrera/fisiología , Adulto , Líquidos Corporales/metabolismo , Bebidas Gaseosas , Carbohidratos de la Dieta/metabolismo , Humanos , Intestino Delgado/metabolismo , Masculino , Resistencia Física/fisiología , Valores de ReferenciaRESUMEN
Ingesting carbohydrate (CHO) beverages during prolonged, continuous heavy exercise results in smaller changes in the plasma concentrations of several cytokines and attenuates a decline in neutrophil function. In contrast, ingesting CHO during prolonged intermittent exercise appears to have negligible influence on these responses, probably due to the overall moderate intensity of these intermittent exercise protocols. Therefore, we examine the effect of CHO ingestion on plasma interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and lipopolysaccharide (LPS)-stimulated neutrophil degranulation responses to high-intensity intermittent running. Six trained male soccer players performed 2 exercise trials, 7 days apart, in a randomized, counterbalanced design. On each occasion, they completed six 15-min periods of intermittent running consisting of maximal sprinting interspersed with less intense periods of running and walking. Subjects consumed either CHO or artificially sweetened placebo (PLA) beverages immediately before and at 15-min intervals during the exercise. At 30 min post-exercise, CHO versus PLA was associated with a higher plasma glucose concentration (p < .01), a lower plasma cortisol and IL-6 concentration (p < .02), and fewer numbers of circulating neutrophils (p < .05). Following the exercise, LPS-stimulated elastase release per neutrophil fell 31% below baseline values on the PLA trial (p = .06) compared with 17% on the CHO trial (p = .30). Plasma TNF-alpha concentration increased following the exercise (main effect of time, p < .001) but was not affected by CHO. These data indicate that CHO ingestion attenuates changes in plasma IL-6 concentration, neutrophil trafficking, and LPS-stimulated neutrophil degranulation in response to intermittent exercise that involves bouts of very high intensity exercise.