Endurance exercise with and without a thermal clamp: effects on
leucocytes and leucocyte subsets.
Cross, M. C., M. W. Radomski, W. P. Vanhelder, S. G. Rhind, & R. J.
Shephard.
Defence & Civil Institute of Environmental Medicine, North York,
Ontario, Depts of Community Health & Anaesthesia, Faculty of
Medicine and School of Physical & Health Education, University of
Toronto
APStracts 3:0119A, 1996.
To test how leucocyte responses to endurance exercise were modified by
clamping body temperature, nine men (27.3 + 6.0 yr) completed four 80
min immersions to mid-chest at water temperatures of 23oC or 39oC;
two tests included 40 min ofcycle ergometer exercise at 65% of
aerobic power. Rectal temperatures when exercising peaked at 39.1 +
0.4oC in the warm water and 37.8 + 0.3oC in the cool water. Sitting
in warm water closely matched the core temperature during exercise in
cool water, whereas when sitting in cool water, rectal temperatures
decreased to 36.4 + 0.6oC. Total and differential white cell counts
were determined by Coulter counter, and cortisol and growth hormone
(GH) concentrations by radioimmunoassay; all data were adjusted for
changes of blood and plasma volumes. Heat clamping during exercise
substantially reduced the rise in white cell, lymphocyte and
granulocyte counts, but not the increase in monocyte count. Clamping
also abolished previously observed associations between cell counts
and cortisol, and weakened associations with GH concentrations. We
conclude that both exercise and a rise of core temperature contribute
to the changes in white cell and subset counts during and immediately
following moderate exercise. Both cortisol and growth hormone
concentrations appear to be mediators of these responses.
Received 7 August 1995; accepted in final form 19 February 1996.
APS Manuscript Number A868-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 March 96