SUSTAINED HYPERHYDRATION WITH GLYCEROL INGESTION

Heavy exercise lasting more than three hours tends to result in dehydr ation, as the fluid intake is less than fluid loss by sweat and urine. Dehydration as small as one percent of body weight has been reported to decrease work capacity. In present and previous studies insensible water loss and sweat are assummed to be the same in both control and e xperimental conditions. Fluid intake less urine volume is utilized as an indicator of euhydration, hypohydration, or hyperhydration. Previou s studies involving glycerol intake describe hyperhydration for 4.5 to 8 hours. The objective of this study was to keep subjects hyperhydrat ed (retention of water) for 32 or 49 hours. The experimental protocol involved ingestion of a large volume of fluid (39.2 or 51.1 ml/kg/d) w ith glycerol (2.9 to 3.1 g/kg/d) and without glycerol. In both Series I (49 h) and Series II (32 h) experiments, the intake of glycerol resu lted in smaller urine volumes. This study demonstrates it is possible to keep human subjects hyperhydrated for extended periods of time and thereby reduce the amount of fluid consumption necessary just prior to or during bouts of negative fluid balance situations.