2007, Piran, Slovenia

2007, Piran, Slovenia 2007, Piran, Slovenia

30.04.2013 Views

Environmental Ergonomics XII Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007 °C sw °C * shivering °C ** °C *** means±S 37.2±0.30 D 0.09±0.14 0.54±0.30 0.63±0.31 * Tre-sw = Sweating threshold Tre-Initial Tre. ** Tre-sw = Initial Tre -Shivering threshold Tre. *** Inter-threshold range= Sweating threshold Tre- Shivering threshold Tre. ACKNOWLEDGEMENTS This study was supported by the Research grant (#15107005, Grant-in-Aid Scientific Research, Japan). REFERENCES Mekjavic, I. B., Sundberg , C. J., Linnasson, D.1991 Core temperature “Null zone”. J. Appl. Physiol. 71(4):1289-1295 Passias, T. C., Meneilly, G. S., Mekjavic I. B. 1996 Effect of hypoglycemia on thermoregulatory responses. J. Appl. Physiol. 80(3):1021-1032 Mekjavic, IB, Eiken, O 2006 Contribution of thermal and nonthermal factors to the regulation of body temperature in humans. J Appl Physiol, 100:2065-2072 Kakitsuba, N., Mekjavic, I.B., Katsuura, T. 2005 Individual variability in the autonomic thermoregulatory responses as related to polymorphism. Proc of the 3rd Int Conf on Human- Environment System, 422-425 252

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

Environmental Ergonomics XII<br />

Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana <strong>2007</strong><br />

°C sw °C * shivering °C ** °C ***<br />

means±S 37.2±0.30<br />

D<br />

0.09±0.14 0.54±0.30 0.63±0.31<br />

* Tre-sw = Sweating threshold Tre-Initial Tre. ** Tre-sw = Initial Tre -Shivering<br />

threshold Tre.<br />

*** Inter-threshold range= Sweating threshold Tre- Shivering threshold Tre.<br />

ACKNOWLEDGEMENTS<br />

This study was supported by the Research grant (#15107005, Grant-in-Aid Scientific<br />

Research, Japan).<br />

REFERENCES<br />

Mekjavic, I. B., Sundberg , C. J., Linnasson, D.1991 Core temperature “Null zone”. J. Appl.<br />

Physiol. 71(4):1289-1295<br />

Passias, T. C., Meneilly, G. S., Mekjavic I. B. 1996 Effect of hypoglycemia on thermoregulatory<br />

responses. J. Appl. Physiol. 80(3):1021-1032<br />

Mekjavic, IB, Eiken, O 2006 Contribution of thermal and nonthermal factors to the regulation<br />

of body temperature in humans. J Appl Physiol, 100:2065-2072<br />

Kakitsuba, N., Mekjavic, I.B., Katsuura, T. 2005 Individual variability in the autonomic<br />

thermoregulatory responses as related to polymorphism. Proc of the 3rd Int Conf on<br />

Human- Environment System, 422-425<br />

252

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