Effects of a low- or a high-carbohydrate diet on performance, energy system contribution, and metabolic responses during supramaximal exercise

Abstract

The purpose of the present study was to examine the effects of a high- or low-carbohydrate (CHO) diet on performance, aerobic and anaerobic contribution, and metabolic responses during supramaximal exercise. Six physically-active men first performed a cycling exercise bout at 115% maximal oxygen uptake to exhaustion after following their normal diet for 48 h (∼50% of CHO, control test). Seventy-two hours after, participants performed a muscle glycogen depletion exercise protocol, followed by either a high- or low-CHO diet (∼70 and 25% of CHO, respectively) for 48 h, in a random, counterbalanced order. After the assigned diet period (48 h), the supramaximal cycling exercise bout (115% maximal oxygen consumption) to exhaustion was repeated. The low-CHO diet reduced time to exhaustion when compared with both the control and the high-CHO diet (-19 and -32%, respectively, p < 0.05). The reduced time to exhaustion following the low-CHO diet was accompanied by a lower total aerobic energy contribution (-39%) compared with the high-CHO diet (p < 0.05). However, the aerobic and anaerobic energy contribution at the shortest time to exhaustion (isotime) was similar among conditions (p > 0.05). The low-CHO diet was associated with a lower blood lactate concentration (p < 0.05), with no effect on the plasma concentration of insulin, glucose and K(+) (p > 0.05). In conclusion, a low-CHO diet reduces both performance and total aerobic energy provision during supramaximal exercise. As peak K(+) concentration was similar, but time to exhaustion shorter, the low-CHO diet was associated with an earlier attainment of peak plasma K(+) concentration.

Effects of carbohydrate intake on time to exhaustion and anaerobic contribution during supramaximal exercise

“…This may explain why carbohydrate intake and a high-carbohydrate diet do not affect time to exhaustion and anaerobic contribution during supramaximal exercise 6,27,28 . In this context, the study data reinforce the abovementioned results, showing that, like higher muscle glycogen content, an exogenous carbohydrate source has no positive effect on performance and anaerobic contribution during supramaximal exercise 5 .…”

“…Bergström & Hultman 4 found that muscle glycogen is not completely depleted during high-intensity exercises, so it is not a limiting factor for exercise performance. Moreover, higher availability of muscle glycogen after a high-carbohydrate meal has no effect on performance during highintensity exercise 5,6 . A plausible explanation for better performance in high-intensity exercises after carbohydrate intake is higher neuromuscular activation, which may lead to higher recruitment of type IIx fibers 7 and concomitantly increase anaerobic glycolysis 8 .…”

Consumo Alimentar, Perfil Antropométrico E Conhecimentos Em Nutrição De Corredores De Rua

“…Lima-Silva et al demonstraram que dietas com baixo teor de carboidratos relacionam-se a eventos de exaustão precoce e queda no rendimento durante o exercício aeróbio supramáximo 27 .…”

“…A ingestão elevada de lipídeos, especialmente entre os homens, pode ter uma provável relação com a baixa ingestão de carboidratos 27 .…”

Children and nutrition

“…fruit, grain products etc.) facilitates the body to store energy fast (Burke et al, 2001;Stevenson et al, 2005;Wallis et al, 2006;Rodriguez et al, 2009;Hulton et al, 2013;Lima-Silva et al, 2013). However, it is also suggested to stick to food with low fiber for easy digestion.…”