Fluid control mechanisms after exercise dehydration

Summary Since the osmocontrol- (osmolality), the renin-angiotensin- (PRA), and the volume control- (central venous pressure, CVP) systems are involved in the maintainance of the salt-water balance, we investigated the pattern of these parameters in the recovery period after exercise dehydration in 13 well trained long-distance runners.On average, after exercise the athletes had lost 3.1% of their body weight (BW). After eating and drinking the BW was still 1.3% below control value, indicative of continuing deficits. Plasma osmolality increased, however, from an average value of 286–290 mosmol/kg after exercise as well as postprandially, but the change was not significant. PRA-Levels rose significantly from 0.167–0.599 ng/ml·h after exercise and decreased to 0.333 ng/ml·h postprandially.CVP was significantly altered after exercise (–3.5 cm H₂O) as well as postprandially (–2.4 cm H₂O).The results suggest that the salt-water balance is maintained by the interplay of all the three systems. In conflicting situations, however, as when intercompartmental water- and solute-shifts take place during the recovery period, the volume control system triggered off by the CVP is the dominant corrective response to the prevailing deficits.Supported by the Bundesinstitut für Sportwissenschaften, Köln