Physiological responses to moderate cold stress in man and the influence of prior prolonged exhaustive exercise

Abstract

SUMMARYA study was undertaken in man to investigate whether during moderate cold stress, the proportion of carbohydrate (CHO) oxidized is increased, and whether prior prolonged exhaustive exercise compromises thermoregulation. Eight euglycaemic men were cooled by a liquid-conditioned suit (1) after an overnight fast (Con) and (2) -2 h after an exercise protocol in which CHO availability was substantially lowered (Post-Ex). The cooling stimulus lasted 90 min (Cooling) and was preceded by a 30 min thermo-neutral baseline phase (Base). In Con, aural temperature (Taural) and the rate of CHO oxidized (CHO..) were not altered from the values at Base during Cooling, whereas the following were increased: the rate of heat production (Hprod, 1.9-fold), thigh electromyographical activity (EMG, -2.5-fold), and the rate of fat oxidized (FAT0., -1.7-fold). In Post-Ex, Taural did not decrease from the value at Base during Cooling, and compared with Con, EMG, CHOOX and the rate of heat loss were not different, whereas Iprod (P 6 0.01), FATOX (P S 0-01) and mean skin temperature (P 6 0.01) were higher, and Taura1 was lower (P 6 0.05). It is concluded that during moderate cold stress, shivering thermogenesis is supported by an increase in the oxidation of fat, and despite an alteration in the initial thermoregulatory responses to Cooling -2 h after exhaustive exercise, thermoregulation was not impaired.

Modulation of carbohydrate and fat utilization by diet, exercise and environment

“…Studies have generally found increases in the relative contribution of carbohydrate and decreases in the relative contribution of fat [36,37] to energy expenditure although some studies have reported no change with moderate cold exposure [38]. During extreme cold shivering is a mechanism to increase energy expenditure and heat production.…”

Fuel selection in shivering humans

“…1990, Glickman‐Weiss et al. 1993, 1994), whereas a few others showed that, under some circumstances, lipid oxidation could provide most of the heat (Martineau & Jacobs 1988, 1989a,b, Weller et al. 1998, Tikuisis et al.…”

Analysis of electromyographic activity of ankle muscles on stable and unstable surfaces with eyes open and closed

“…Electromyography (either alone or in combination with other biomechanical methods) offers important information on the behavior of muscles when submitted to different types of load as well as diverse execution angles and velocities (Silva and Gonçalvez, 2003). This method also assesses myoelectric behavior under different circumstances, such as body and room temperature, neuromuscular training, etc (Weller et al, 1998;Oksa et al, 2002;Racinais et al, 2005;Shin et al, 2006).…”