Lima-Silva, Adriano E, Pires, Flavio O, Bertuzzi, Rômulo, Silva-Cavalcante, Marcos David, Oliveira, Rodrigo, Kiss, Maria A and Bishop, David ORCID: 0000-0002-6956-9188 (2013) Effects of a low- or a high-carbohydrate diet on performance, energy system contribution, and metabolic responses during supramaximal exercise. Applied Physiology, Nutrition, and Metabolism, 38 (9). pp. 928-934. ISSN 1715-5312 (print) 1715-5320 (online)

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.

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