2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
POSTEXERCISE CHANGES IN BODY HEAT CONTENT MEASURED
USING CALORIMETRY
Glen P. Kenny, Paul Webb, Michel DuCharme, Francis D. Reardon, Ollie Jay
Laboratory for Human Bioenergetics and Environmental Physiology, School of Human
Kinetics, University of Ottawa, Ottawa, ON, Canada. K1N 6N5.
Contact Person: ojay@uottawa.ca
Changes in body heat content (∆Hb) measured using whole-body direct calorimetry, were
compared after 60-min of semi-recumbent cycle ergometry at 40% of •
VO2peak and after 60min
of stationary semi-recumbent postexercise recovery, while concurrently measuring core
and muscle temperatures. Six male participants were investigated using the Snellen air
calorimeter regulated at 30ºC and 30% relative humidity. Core temperature was measured
using esophageal (Tes), rectal (Tre) and aural canal (Tau) temperature, while regional muscle
temperature was measured from vastus lateralis (Tvl), triceps brachii (Ttb) and upper trapezius
(Tut) temperature. Following exercise, ∆Hb was 289 ±15 kJ, paralleled by elevations of 0.82
±0.20°C, 0.53 ±0.07°C and 0.76 ±0.22°C in Tes, Tre and Tau respectively, and 2.45 ±0.26°C,
2.27 ±0.23°C and 0.78 ±0.08°C in Tvl, Ttb and Tut respectively. Following 60-min recovery,
∆Hb was 148 ±40 kJ with corresponding elevations of 0.22 ±0.06°C, 0.20 ±0.04ºC and 0.15
±0.04ºC above pre-exercise rest for Tes, Tre and Tau respectively, and 1.00 ±0.19°C and 0.93
±0.21°C for Tvl and Ttb. At end-exercise and end-recovery, the rate of metabolic heat
production ( •
M- •
W: metabolic rate minus external work rate) was similar to the rate of wholebody
heat loss ( •
HL). •
M- •
W returned to pre-exercise resting levels after 10-min of postexercise
recovery, however, the exponential rate of increase of •
HL during exercise (time constant (τ) =
11.9 ±1.4 min) was significantly greater than the exponential rate of decay during
postexercise recovery (τ = 7.5 ±0.8 min). It is concluded that a substantial elevation in ∆Hb
remains after prolonged postexercise recovery without a sustained elevation in •
M- •
W, due to a
greater rate of change in •
HL during recovery than during 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 Lindsay Nettlefold for her technical support
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