Exercise hyperpnea and hyperthermia in humans.
White, Matthew D., and Michel Cabanac.
Dept. Physiol., Laval Univ., Qu[acute]ebec, GIK 7P4 Canada
APStracts 3:0239A, 1996.
The problem of the relative hyperpnea occurring at high levels of
exercise remains unresolved. This study examined whether the
hyperpnea observed in humans during exercise at about 70 percent of
maximal work capacity was related the evolution of cranial (tympanic)
and thoracic (esophageal) temperatures. Six trained male subjects
pedaled at approximately 60 rpm on an electrically braked cycle
ergometer in a climatic chamber at 25 degrees C and approximately 35%
RH in two sessions. The subjects pedaled until their exhaustion in
two sessions. In one session work rate was increased by 40 W each 2
min in the other session and by 20 W each 2 min. In both exercise
sessions core temperature thresholds for ventilation were evident and
subsequently tympanic and esophageal diverged. This suggested that
the hyperpnea observed after about 70 percent of an individuals
maximum work rate, could be a thermolytic response related to
selective brain cooling in humans.
Received 8 September 1995; accepted in final form 25 April 1996.
APS Manuscript Number A983-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 May 96