Circulatory effects of fluid loss and fluid intake during exercise

Abstract

Abstract Cardiorespiratory responses to two levels of exercise (133 and 200 W) on a bicycle ergometer were measured in nine subjects before and after a 1‐h outdoor run of 12.8 km completed in ambient temperatures of 20–25° C. After the run, the subjects showed a mean weight loss of 1.49 kg; the laboratory exercises produced higher mean levels of O2 consumption than before the run (1.91 and 2.66 1 min‐1 compared with 1.80 and 2.46 1 min‐1) and higher mean heart rates (141 and 158 beats min‐1 compared with 115 and 140 beats min‐1); and lower levels of stroke volume (83 and 85 ml compared with 109 and 101 ml) and of cardiac output (11.6 and 13.3 1 min‐1 compared with 12.6 and 14.1 1 min‐1). Five subjects were studied in a similar way on a second occasion when they consumed 1.25 1 of a dextrose‐electrolyte solution during the first 45 min of the outdoor run. Differences in the exercise variables measured before and after the outdoor run were now small or insignificant. It is postulated that in the first study...