Physiological responses to a cold, wet, and windy environment during prolonged intermittent walking

Abstract

The potentially deleterious influence of body cooling on the thermoregulatory and metabolic responses to prolonged walking exercise has not been established. To address this problem, 10 men completed a 6-h intermittent (15 min rest, 45 min exercise) walking protocol in a thermoneutral (+15 degrees C) condition (Neutral) and a cold (+5 degrees C), wet, and windy condition (Cold). The first two exercise periods were conducted at a higher intensity (Higher, 6 km/h and 10% incline) than the subsequent four exercise periods (Lower, 5 km/h and 0% incline). Rectal temperature was lower and heart rate no different in Cold compared with Neutral, whereas the following were higher: oxygen consumption, respiratory exchange ratio, plasma norepinephrine and epinephrine, and blood lactate and glucose. There was no environmental influence on these variables during Higher. In conclusion, heat production during Lower was not sufficient to offset heat loss to the cold environment, and the resulting reduction in rectal temperature and metabolic perturbations may be detrimental if exercise is prolonged.

100 Years Since Scott Reached the Pole: A Century of Learning About the Physiological Demands of Antarctica

“…In recent times there have been a number of experiments specifically looking at physiological responses to exercise in cold, wet, and windy conditions. In a wet, windy environment with an ambient temperature of 5°C, so long as exercise intensity is fairly high, for example, a strong pace of walking, there is no change in core body temperature or rate of energy expenditure compared with thermoneutral conditions (129). Indeed, during periods of man-hauling, sweating and peripheral vasodilation occurs, necessary to dissipate the excess heat produced (60).…”

“…Indeed, during periods of man-hauling, sweating and peripheral vasodilation occurs, necessary to dissipate the excess heat produced (60). However, if the work rate is lower, even though this still represents walking at a standard pace (129), core temperature decreases by around 1°C while rate of energy expenditure rises (probably primarily due to shivering; Ref. 87), indicating that heat production from the exercise does not offset heat lost to the cold environment.…”

The effects of exhaustive exercise on thermoregulatory fatigue during cold exposure

“…If these volunteers were subjected to wet-cold conditions in a scenario where they could not escape the cold after discontinuing exercise, shivering alone would be insufficient to offset heat loss, and core temperature would fall. Weller et al (14) and Thompson and Hayward (12) demonstrate this elegantly in their studies when exercise intensity decreases during prolonged cold-wet exposure. Thus, physical exertion affects the ability to maintain normal body temperatures during cold exposure via both direct (i.e.…”

“…On D3 and D7, -2.5 hours (140-170 min) elapsed between the end of the last daily exercise session and the subsequent CW. The CW was modified from an experimental protocol described by Weller et al (14). Briefly, CW consisted of 360-min intermittent treadmill walking (six cycles of 10-min standing rest in the rain, 45-min walking, 5-min for transition between rest and walking) in an environmental chamber with air temperature set at 5°C.…”

Mild Decrease in Skin Temperature Reduces the Heart Rate during Moderate Exercise

“…Exposure to severe cold with a decrease in rectal and skin temperatures enhances fat oxidation during running and walking [3]. In addition, participants exposed to cold who were shivering had increased carbohydrate utilization during walking at low intensity compared to those who were not shivering [4]. In contrast, lipid and carbohydrate oxidation during submaximal exercise did not differ…”