Metabolic Responses to Sago, Soy and Sago+Soy Combined Supplementations during Endurance Cycling Performance Followed by Time Trial Performance in the Heat

The aim of the present study was to investigate the effect of Sago (Sa), Soy (So), combined iso–caloric Sago+Soy (SS) supplementations during endurance cycling on plasma glucose and plasma insulin responses, in the heat (31℃, 70% relative humidity). Twelve well–trained male cyclists (19.0±5.6 yr, 170.8±7.6 cm, 60.1±11.2 kg, and 56.5±6.5 mL.kg-1.min-1 VO2 max) participated in four experimental trials. The design of the trials were a randomized single–blind placebo–controlled crossover comprising 90 min of steady–state cycling on an ergometer at 60% of VO2max followed by a 20–km time trial performance (TT). The participants of the study were supplemented 5 times at 0, 20, 40, 60, and 80 minutes in the steady–state cycling. Sa, So, and SS supplements provided 7.5% Sago, 7.5% Soy, and 6.0% Sago + 1.5% Soy respectively. Plasma glucose concentrations (PG) reached peak at 60 min after ingestions of Sa and SS as compared to baseline. At the end of the TT, PG reduced significantly to the baseline. Plasma insulin concentrations (PI) were increased in all trials, but reduced gradually to the baseline. The concentration of plasma free fatty acids (FFA) increased gradually during the steady–state cycling and TT, and FFA was significantly higher in the P and So than the Sa and SS trials. At the end of the steady–state cycling, the plasma lactate concentration (LACT) reached to its lowest concentrations and at the end of the TT was enhanced significantly in all trials. These results suggest that sago and soy supplements increase the PG and PI during endurance exercise in the heat. These data add to the growing body of knowledge concerning endurance athletes’ glycemic and insulinemic responses to carbohydrate, protein and a combined carbohydrate-protein consumptions in the heat.