Carbohydrate loading and supplementation in endurance-trained women runners

Abstract

The purpose of this study was to examine the effect of carbohydrate (CHO) augmentation on endurance performance and substrate utilization in aerobically trained women. Eight endurance-trained women completed a 24.2-km (15 mile) self-paced treadmill performance run under three conditions: CHO supplementation (S), CHO loading and supplementation (L+S), and placebo (P). Dietary CHO was approximately 75% of energy intake for L+S and approximately 50% for both S and P. A 6% CHO-electrolyte solution (S and L+S) or placebo (P) was ingested preexercise (6 ml/kg) and every 20 min during exercise (3 ml/kg). Blood glucose was significantly higher at 40, 60, and 100 min during L+S, and at 60, 80, and 100 min during S compared with P (P < 0.05). Blood lactate was significantly higher (P < 0.05) during L+S than S and P. Blood glycerol was significantly lower (P < 0.05) at 20, 80, and 100 min during L+S, and at 80 and 100 min during S than P. The proportion of CHO (%) utilized during exercise was significantly higher (P < 0.05) during L+S (71.3 +/- 3.8%) and S (67.3 +/- 4.3%) than P (59.2 +/- 4.6%). Performance times (P > 0.05) were 132.5 +/- 6.3 min (S), 134.4 +/- 6.3 min (L+S), and 136.6 +/- 7.9 min (P). In conclusion, it appears that when CHO availability in women is increased through CHO loading and/or CHO supplementation, there is a concomitant increase in CHO utilization. However, this may not necessarily result in significantly improved performance.

Efeitos bioquímicos da suplementação de carboidratos após uma competição simulada de Short Duathlon Terrestre

“…Verifica-se, também, que a suplementação de CHO (maltodextrina) produz um aumento nos estoques de glicogênio muscular, permitindo que a competição se prolongue ou que a performance seja melhorada, mediante o retardo do início da fadiga. Este atraso da fadiga deve-se, principalmente, à prevenção do declínio da concentração da glicose sanguínea, a qual facilita proporções elevadas da oxidação de CHO durante os estágios finais da competição (23). Com relação ao aumento da glicemia na fase pós-competição do G1, quando comparado com o G2, verifica-se que esse resultado corrobora os de outros estudos (28,29,30), que demonstraram que os níveis da glicemia são mais elevados após a ingestão de um suplemento à base de maltodextrina, quando comparado com outros tipos de CHO e placebo.…”

The physiology of tapering

“…A number of studies support this contention, reporting no increases in muscle glycogen content or performance enhancement in response to CHO loading in highly trained female athletes (Andrews et al 2003). Two key factors underpinning the absence of improvement in muscle glycogen content and performance observed in these studies, however, are the phase of the menstrual cycle and quantity of CHO consumed during the loading period.…”

“…Thus, the equivocal findings reported from studies examining female athletes are probably due to testing during the follicular phase of the menstrual cycle (Andrews et al 2003). In addition to menstrual cycle phase, insufficient quantities of CHO (<8.0 g.kg −1 .day −1 ) are often ingested by female athletes in studies reporting no changes in muscle glycogen content and performance enhancement following glycogen loading (Andrews et al 2003). Indeed, in those studies conducted during the luteal phase with CHO consumption <8.0 g.kg −1 .day −1 female athletes exhibited similar levels of muscle glycogen and performance enhancement to their male counterparts (Tarnapolsky et al 2001).…”

“…In particular, glycogen loading during the 5-10 days following the first day of menses reduces the impact of gonadotrophic hormones and enhances glycogen loading. Thus, the equivocal findings reported from studies examining female athletes are probably due to testing during the follicular phase of the menstrual cycle (Andrews et al 2003). In addition to menstrual cycle phase, insufficient quantities of CHO (<8.0 g.kg −1 .day −1 ) are often ingested by female athletes in studies reporting no changes in muscle glycogen content and performance enhancement following glycogen loading (Andrews et al 2003).…”

Metabolismo energético em atletas de endurance é diferente entre os sexos

“…Em outro estudo, que também avaliou somente mulheres atletas, Andrews et al 40 verificaram o efeito da ingestão de carboidratos em exercícios de endurance (corrida de 24 km). Oito mulheres durante a fase folicular do ciclo menstrual foram avaliadas em três momentos: utilizando placebo, suplemento de carboidratos (solução de eletrólitos com 6% do substrato) e dieta de sobrecarga glicídica (75% do VET) com suplemento de carboidratos.…”