Despite evidence of hypervolemia following endurance training, there is little information regarding corresponding extravascular fluid volumes. Quantification of such volumes relies upon radionuclide dilution methods, previously hampered by the loss of plasma albumin. It was our purpose to measure human body-fluid distribution in eight endurance-trained males, using a simultaneous radionuclide dilution technique, incorporating radioiodinated serum fibronogen (RISF). Fluid distribution was measured on three occasions, using 2 μCi of RISF, 8 μCi of 51Cr-labeled erythrocytes, and 20μCi of Na82Br and 450 μCi of 3H2O; to measure PV, erythrocyte (RCV), extracellular (ECFV), and total-body water (TBW) volumes, respectively. Respective volume means, 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 reliable modification to previous methods, and revealed a body-fluid expansion in endurance-trained males. It was concluded that such subjects were hyperhydrated, possessing proportionately expanded fluid volumes throughout both intravascular and extravascular spaces. This was attributed to training history and accompanying reductions in adiposity.
Department of Biomedical Science, University of Wollongong, Wollongong; and Haematology Department, Illawarra Regional Hospital, AUSTRALIA
Submitted for publication September 1994.
Accepted for publication September 1995.
The authors wish to acknowledge the invaluable assistance provided by the staff of the Haematology Department (Illawarra Regional Hospital, Wollongong) during the development and completion of this project.
This study was partially funded by grants from the Australian Institute of Nuclear Science and Engineering, and the Australian Research Council.
Present address for G.J.M.: Queensland Academy of Sport, G.P.O. Box 354, Brisbane, QLD 4001, Australia.
Present address for I.L.M. and D.A.M.C.: Haematology Department, Illawarra Regional Hospital, Wollongong, NSW 2500, Australia.
Address for correspondence: Nigel A.S. Taylor, Ph.D., Dept. of Biomedical Science, University of Wollongong, Northfields Ave., Wollongong, NSW 2522, Australia.