WHOLE-BODY HYPERHYDRATION IN ENDURANCE-TRAINED MALES DETERMINED USINGRADIONUCLIDE DILUTION

Despite evidence of hypervolemia following endurance training, there i s little information regarding corresponding extravascular fluid volum es. Quantification of such volumes relies upon radionuclide dilution m ethods, previously hampered by the loss of plasma albumin. It was our purpose to measure human body fluid distribution in eight endurance-tr ained males, using a simultaneous radionuclide dilution technique, inc orporating radioiodinated serum fibronogen (RISF). Fluid distribution was measured on three occasions, using 2 mu Ci of RISF, 8 mu Ci of Cr- 51-labeled erythrocytes, and 20 mu Ci of (NaBr)-Br-82 and 450 mu Ci of (H2O)-H-3; to measure PV, erythrocyte (RCV), extracellular (ECFV), an d total-body water (TBW) volumes, respectively. Respective volume mean s, standard deviations, and coefficients of variation were: 46.6 (+/-4 .9; 8.44%), 33.3 (+/-2.9; 3.89%), 258.1 (+/-12.1; 4.93%), and 654.2 (/-13.4; 3.24%) ml . kg(-1). The incorporation of RISF provided a relia ble modification to previous methods, and revealed a body-fluid expans ion in endurance-trained males. It was concluded that such subjects we re hyperhydrated, possessing proportionately expanded fluid volumes th roughout both intravascular and extravascular spaces. This was attribu ted to training history and accompanying reductions in adiposity.