- Meeting abstract
- Open Access
Metabolic costs of physiological heat stress responses - Q10 coefficients relating oxygen consumption to body temperature
Extreme Physiology & Medicine volume 4, Article number: A103 (2015)
Q10 describes the influence of temperature on physiological processes as the ratio of the rate of a physiological process at a particular temperature to the rate at a temperature 10 °C lower . In terms of rates of oxygen consumption (VO2) related to rectal temperatures (tre), this can be written as :
Q10 varies between 2 and 3 in biological systems , and Q10 = 2 is applied in modelling the rate of metabolic heat production in relation to body temperature [3, 4]. This paper aims to determine Q10 for the influence of body temperature on oxygen consumption for light work in warm environments.
Data originated from 216 laboratory experiments  consisting of individual series of 14 to 39 trials performed by eleven acclimatised semi-nude young males (Icl=.1 clo) who walked 4 km.h-1 on the level for at least 3 hours under different combinations of water vapour pressure (range 0.3 - 5.2 kPa) and air temperature (range 20 - 55 °C) with air velocity of 0.3 m.s-1 and mean radiant temperature equal to air temperature. Mean values of tre and VO2 over the third hour of exposure were submitted to linear regression analyses, which were performed separately for the 11 individual series relating VO2 directly to tre and also using the logarithmised Eq. 1b (with tre,ref = 36.8 °C). Overall regression parameters were calculated by random coefficient linear mixed models considering the correlation within the individual series. Q10 coefficients were obtained as the exponentiated slopes of the fitted logarithmised Eq. 1b.
Regression analyses showed a statistically significant (p < 0.01) increase of VO2 with tre (Figure 1A) with inter-individually varying slopes, which resulted in Q10 values varying largely between 1 (indicating no influence of tre on VO2) and 10 (Figure 1B). The overall Q10 was 2.1 with 95% confidence interval (CI) 1.3 - 3.5.
Discussion and conclusion
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