The effect of body cooling on oxygen transport during exercise

The capability to transport oxygen to muscle limits the ability to exercise. The purpose of this review is to consider the effects of body cooling on the oxygen transport and therefore exercise capacity. Body cooling results in an increase in resting metabolism that is proportional to the decrease in core temperature (Tc). Furthermore, the energy cost of exercise is increased (10-40%) by a 0.5-1.5 degrees C decrease in Tc. The capability to supply oxygen to meet the increased cost of activity is also reduced by 10-40% for a decrease in Tc of 0.5-1.5 degrees C. The reduced oxygen delivery is a result of a combination of decreased respiratory effectiveness, cardiac function, and muscle blood flow. Other than at rest, cardiac output in air or water with and without body cooling increases similarly with oxygen consumption (6 1/1 O2). Body cooling does result in a reduction of maximal heart rate and cardiac output. We postulate that the primary limitation to oxygen transport is a persistent vasoconstriction mediated by the sympathetic system, to increase body insulation, that blunts the local metabolically mediated exercise hyperemia.