FLUID BALANCE AND RENAL RESPONSE FOLLOWING DEHYDRATING EXERCISE IN WELL-TRAINED MEN AND WOMEN

We examined the recovery of plasma volume, plasma osmolality, renal wa ter and sodium handling and fluid-regulating hormones to dehydrating e xercise in well-trained women and compared them to men. Ten male and e ight female athletes cycled at anaerobic threshold at an ambient tempe rature of 32 degrees C until dehydration by 3% of their body mass (m(b )). After exercise, they drank water equal to 1% m(b) and rested for 2 40 min. Plasma renin activity (PRA), serum aldosterone [ALDO](s), plas ma arginine vasopressin [AVP](pl), norepinephrine concentrations and p lasma osmolality (Osm(pl)) were determined at baseline, end of exercis e, 30, 60, 120 and 240 min postexercise. Urine was collected at baseli ne, end of exercise, 60, 120 and 240 min postexercise. Renal free wate r and sodium handling were assessed. The recovery of OSM(pl) and plasm a volume occurred within the first 60 min of recovery and at similar r ates between the groups. However, women had lower PRA at the end of ex ercise (P = 0.05), an earlier recovery of [ALDO](s), and a slower [AVP ](pl) recovery. Overall fluid balance was similar between the men and women, as were the early recovery of renal free water clearance (C-H2O ). During the last 120 min of recovery C-H2O was more negative (greate r water reabsorption) and fractional sodium excretion was increased in the women compared to the men. Despite small differences in sodium an d water reabsorption following dehydration, it appears from other stud y that recovery from dehydrating exercise in well-trained men and wome n is remarkably similar.