2007, Piran, Slovenia

Non-thermal factors
RATES OF TOTAL HEAT LOSS AT TWO DIFFERENT RATES OF
POSTEXERCISE METABOLIC HEAT PRODUCTION
Daniel Gagnon, Ollie Jay, Glen P. Kenny
Laboratory for Human Bioenergetics and Environmental Physiology, School of Human
Kinetics, University of Ottawa, Ottawa, ON, Canada. K1N 6N5.
Contact person: ojay@uottawa.ca
Previous studies have reported a rapid reduction in heat loss responses during the early stages
of inactive recovery from exercise, despite an elevated core temperature. However, greater
heat loss responses during active recovery are paralleled by similar core temperature
elevations to inactive recovery. The purpose of this study was to examine the changes in the
rate of total heat loss during recovery at two different levels of metabolic heat production with
similar core temperatures throughout. Seven male volunteers exercised at 75% of •
VO2peak on
a semi-recumbent cycle ergometer housed within the Snellen whole-body air calorimeter for
15-min followed by 30-min of recovery with (active) or without (inactive) loadless pedalling.
Core temperature was measured using esophageal temperature (Tes) and the rates of total heat
production ( •
M- •
W) and total heat loss ( •
HL) were measured by whole-body calorimetry.
Changes in body heat content and Tes, as well as •
M- •
HL were similar at the end of
W and •
exercise in both conditions. At the end of the recovery period, in the active and inactive mode
respectively, •
M- •
W was 210 ± 31 W and 119 ± 12 W, and •
HL was 246 ± 31 W and 202 ± 25
W. The magnitude of the total reduction in •
HL was significantly greater (p≤0.05) for inactive
recovery, while the rate of exponential decay in •
HL were not different between recovery
conditions (p>0.05). Furthermore, changes from baseline in Tes were not different between
conditions at any time point (p>0.05). These results suggest that changes in heat loss
responses that determine the rate of change in total heat loss appear to be dependent upon the
rate of metabolic heat production, and not upon changes in core temperature during recovery
from exercise.
This research was supported by a Discovery Grant from the Natural Sciences and Engineering
Research Council of Canada and a U.S. Army Medical Research Acquisition Activity. We
would like to acknowledge Candice Brown, Andrea McCarthy and Matthew Kennedy for
their technical support.
253