Effects of preexercise carbohydrate ingestion on mountain bike performance.

Department of Biomedical Science, University of Wollongong, NSW, Australia.
Medicine &amp Science in Sports &amp Exercise (Impact Factor: 4.46). 09/2004; 36(9):1602-9. DOI: 10.1249/01.MSS.0000139805.91675.5B
Source: PubMed

ABSTRACT This study examined the performance and metabolic effects of consuming 1.0 (LC) and 3.0 (HC) grams of carbohydrate (CHO) per kilogram body mass (BM), 3 h before a 93-min simulated mountain bike race.
After two familiarization trials, eight male subjects undertook two CHO trials in a double-blind counterbalanced fashion on a cycle ergometer. The HC meal was supplemented with maltodextrin while maintaining the same glycemic index and apparent volume of food as the LC meal. Stochastic cycling was undertaken for 93 min (4 x 22.50-min laps) with performance measured as the total work performed in 6 x 30-s periods each lap during the test.
Performance in lap 1 was better with LC (P < 0.03) whereas performance in lap 4 was better with HC (P < 0.02). Overall performance was 3% greater in HC compared with LC (NS, P = 0.13). Serum glucose was significantly lower (P < 0.04) in HC immediately before the mountain bike test (180 min postprandial) and at 10 min into the test (P < 0.01). Gastrointestinal comfort decreased similarly for both trials over time (P < 0.05).
These data suggest that ingestion of 3.0 g x kg(-1) BM of CHO 3 h before a 93-min mountain bike simulated race does not produce a statistically significant improvement in overall performance compared with 1.0 g x kg(-1) BM. However, in real terms, a 3% performance improvement may benefit athletes in a race situation. Differences in performance during the first and last laps indicate a variation in pacing strategies that may have resulted from differing blood glucose levels between trials.

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    ABSTRACT: RAMD Originales Nutritional analysis of diet at base camp of a seven thousand-metre mountain in the Himalayas Pre-exercise high concentration carbohydrate supplementation impairs the performance on high intensity cycling exercise Repercusión de la hipercifosis sobre variables antropométricas y funcionales Frecuencia cardíaca máxima obtenida y predicha: estudio retrospectivo en brasileños (artículo en portugués) Revisiones Efectos metabólicos, renales y óseos de las dietas hiperproteicas. Papel regulador del ejercicio Evidencias para la prescripción de ejercicio físico en pacientes con fibromialgia La periodización del entrenamiento y las cuestiones emergentes: el caso de los deportes de equipo (artículo en portugués) Indexada en SCOPUS R e v i s t a A n d a l u z a d e Medicina del Deporte Rev Andal Med Deporte. 2010;3(4):133-137 R E S U M E N La suplementación pre-ejercicio con carbohidrato de alta concentración perjudica el rendimiento en el ejercicio de alta intensidad en bicicleta Objetivos. Evaluar los efectos de la suplementación pre-ejercicio de hidratos de carbono de alta concentración en el rendimiento y respuestas cardiovasculares, metabólicas y hormonales durante el ejercicio de alta intensidad en bicicleta. Método. Participaron en el estudio siete ciclistas varones (28,7 ± 5,4 años; 65,2 ± 4,7 kg de peso corporal), que realizaron dos ensayos con placebo (PLA) e hidratos de carbono (CHO), con ejercicio continuo en un ritmo de trabajo del 80% del VO 2máx , hasta el agotamiento. Los ciclistas recibieron 5 -1 de una solución diluida de maltodextrina en una concentración de 10% (CHO) o placebo (PLA) a los 60, 45 y 30 minutos antes del ejercicio. Resultados. Se observó una reducción de 5,4% en el tiempo hasta el agotamiento en el ensayo de CHO en comparación con el grupo PLA. En ambos ensayos, la glucosa y los niveles de lactato fueron mayores en el estado posterior al ejercicio en comparación con los valores previos (p < 0,05). Los niveles de ácidos grasos libres fueron menores en el grupo CHO que en el grupo PLA tanto antes como después del ejercicio (p < 0,05). La insulinemia fue mayor en la condición pre-ejercicio en el grupo CHO (42,7 ± 3,6 μ -1) en comparación con el grupo PLA (11,8 ± 3,3 μ -1) (p < 0,05), y disminuyó hacia 23,8 ± 5,1 μ -1 durante el ejercicio, después de la ingesta de CHO (p < 0,05). No hubo diferencias significativas en el cortisol plasmático entre los dos ensayos (p > 0,05). Conclusiones. La suplementación pre-ejercicio con CHO de alta concentración resulta en un menor rendimiento en ejercicio de alta intensidad en bicicleta y en una disminución de los niveles de ácidos grasos libres. Objectives. To evaluate the effects of pre-exercise high concentration carbohydrate supplementation on performance, cardiovascular, metabolic and hormonal responses during high intensity cycling exercise. Method. Seven male cyclists (28.7 ± 5.4 years; 65.2 ± 4.7 kg body weight), who performed two continuous exercise trials under placebo (PLA) or carbohydrate (CHO) ingestion at a work rate of 80% VO 2max until exhaustion, participated in the study. The cyclists received 5 of a maltodextrin solution diluted at a concentration of 10% (CHO) or placebo (PLA) at 60, 45 and 30 min pre-exercise. Results. A 5.4% reduction in the time to exhaustion was observed in the CHO trial compared to the PLA trial. In both trials, glucose and lactate levels were higher in the post-trial condition compared to pre-exercise values (p < 0.05). Free fatty acid levels were lower in the CHO group than in the PLA group both before and after the trial (p < 0.05). Insulinemia was higher during the pre-trial in the CHO group (42.7 ± 3.6 μ compared to the PLA condition (11.8 ± 3.3 μ (p < 0.05), and even decreased to 23.8 ± 5.1 μ during exercise after CHO intake (p < 0.05). No significant differences in plasma cortisol were observed between the two trials (p > 0.05). Conclusions. Pre-exercise high concentration CHO supplementation resulted in impaired performance in high intensity cycling exercise and decreased free fatty acid levels. © 2010 Revista Andaluza de Medicina del Deporte.
    Revista Andaluza de Medicina del Deporte 01/2010; 3(4):133-137.
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    ABSTRACT: The majority of lightweight rowers undertake acute weight loss prior to competition. Given the competitive advantage afforded to larger, more muscular rowers over their smaller counterparts, the use of moderate, acute weight loss may be justified, at least among larger, leaner athletes who struggle to achieve the specified body mass requirement and have limited potential for further body mass loss via reductions in body fat. The performance implications of moderate acute weight loss appear to be small on the ergometer and may be even less on water, at least when aggressive recovery strategies are adopted between weigh-in and racing. Furthermore, any performance implications of acute weight loss are not exacerbated when such weight loss is undertaken repeatedly throughout the course of a regatta, and may even be eliminated when aggressive recovery strategies are introduced before and after racing. The combination of adequate sodium, fluid and carbohydrate in line with current guidelines results in the best performances. While the performance implications of modest acute weight loss may still need to be considered in regard to competition outcome, chronic body mass strategies may not be without performance implications. This is especially the case for athletes who have very low levels of body fat and/or athletes who decrease their body mass too quickly. Further studies are needed to address the degree of weight loss that can be tolerated with minimal health and/or performance implications, and the optimal time frame over which this should occur. Possible adaptation to the physiological state that accompanies acute weight loss also warrants investigation.
    British Journal of Sports Medicine 09/2014; 48(21). DOI:10.1136/bjsports-2014-093918 · 4.17 Impact Factor
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    Journal Biology of Exercise 01/2008; DOI:10.4127/jbe.2008.4.17-28

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