Effects of glucose ingestion at the onset of moderate-intensity, prolonged exercise in women as compared to men

Abstract

To test glucose tolerance during exercise, the effects of oral glucose ingestion (0.5 g · kg⁻¹) on plasma glucose and hormonal responses (insulin, catecholamines) were investigated in 11 women [mean (SEM) age 21.6 (1.3) years] and 10 men [22.0 (0.3) years] during cycle ergometer exercise (30 min at 60% maximum oxygen consumption, V˙O_2max). The two groups exhibited similar V˙O_2max values, when expressed per kg of lean body mass. Venous blood samples (5 ml) were withdrawn immediately before the exercise, during the exercise (at 3, 5, 10, 15 and 30 min) and at the 30th min of the recovery period. Glucose was ingested orally between the 2nd and the 3rd min of the exercise. As compared to men, plasma glucose concentrations were lower in women during exercise (P < 0.05 at 3, 15 and 30 min) and at the 30th min of the recovery period (P < 0.001), while plasma insulin concentrations were higher in women during exercise (P < 0.05 at 3, 15 and 30 min). The ratio of the area under the curve for glucose over the area under the curve for insulin was lower in women during exercise (P < 0.0002). A linear relationship between glucose and insulin concentrations was found only for women during exercise (r = 0.615, P < 0.0001). No gender difference was observed for the catecholamine concentration during exercise. In conclusion, this study postulates that an oral glucose load given at the onset of a prolonged and moderate exercise bout induced lesser plasma glucose and greater insulin concentrations in women as compared to men. These data argue in favour of a greater glucose tolerance in women during exercise.