title: 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.
authors.affiliation: a Sports Science Research Group, Federal University of Alagoas. Lorival Melo Mota Avenue S/N, Tabuleiro do Martins, Maceió, Alagoas 57072-970, Brazil.
authors.forename: Adriano E
authors.initials: AE
authors.lastname: Lima-Silva
authors.forename: Flavio O
authors.initials: FO
authors.lastname: Pires
authors.forename: Romulo
authors.initials: R
authors.lastname: Bertuzzi
authors.forename: Marcos D
authors.initials: MD
authors.lastname: Silva-Cavalcante
authors.forename: Rodrigo S F
authors.initials: RS
authors.lastname: Oliveira
authors.forename: Maria Augusta
authors.initials: MA
authors.lastname: Kiss
authors.forename: David
authors.initials: D
authors.lastname: Bishop
mesh_terms: D004032:Diet; D004040:Dietary Carbohydrates / Q000378:metabolism; D015444:Exercise; D006801:Humans; D010101:Oxygen Consumption; D005082:Physical Exertion
chemical_list: D004040:Dietary Carbohydrates