The effect of a Live-high Train-high exercise regimen on behavioural temperature regulation.

Abstract

Acute hypoxia alters the threshold for sensation of cutaneous thermal stimuli. We hypothesised that hypoxia-induced alterations in cutaneous temperature sensation may lead to modulation of the perception of temperature, ultimately influencing behavioural thermoregulation and that the magnitude of this effect could be influenced by daily physical training. Fourteen men were confined 10 days to a normobaric hypoxic environment (PIO2=88.2±0.6mmHg, corresponding to 4175m elevation). Subjects were randomly assigned to a non-exercising (Live-high, LH, N=6), or exercising group (Live-high Train-high, LH-TH, N=8) comprised of 1-h bouts of cycle ergometry, twice daily, at a work-rate equivalent to 50% hypoxic peak power output. A subset of subjects (N=5) also completed a control trial under normoxic conditions. The thermal comfort zone (TCZ) was determined in normoxia, and during hypoxic confinement days 2 (HC2) and 10 (HC10) in both groups using a water-perfused suit in which water temperature was regulated by the subjects within a range, they deemed thermally comfortable. Mean skin temperature and proximal-distal temperature gradients (two sites: forearm-fingertip, calf-toe) were recorded each minute throughout the 60-min protocol. The average width of the TCZ did not differ between the control group (9.0±6.9°C), and the LH and LH-TH groups on days HC2 (7.2±4.2°C) and HC10 (10.2±7.5°C) of the hypoxic exposure (p=0.256). [Formula: see text] was marginally higher on HC2 (35.9±1.0°C) compared to control (34.9±0.8°C, p=0.040), but not on HC10 (35.6±1.0°C), reflecting the responses of hand perfusion. There was a little systematic effect of hypoxia or exercise training on TCZ magnitude or boundary temperatures.