The human thermal portrait and its relations with aerobic working capacity and the blood lactate level

In a study on 53 healthy male volunteers with the use of an infrared thermograph, data that the thermal portrait, i.e., skin temperature distribution, under the conditions of muscular rest and minimal chemical thermoregulation activation is related to the maximal aerobic capacity (r = + 0.6) and the lactate level after critical muscle load (r = −0.7) were obtained. A series of pilot experiments on six volunteers showed that acute regional cooling (by placing feet into ice-cold water for 1 min) led to temperature rise in some local areas of the breast and back skin and increase in oxygen uptake, pulmonary ventilation and the respiratory quotient. Simultaneously, the lactate level in peripheral blood was reduced. On the basis of these results, it was assumed that brown adipose tissue (BAT) activity influenced the thermal portrait formation in the case of environmental temperature below thermoneutral. This hypothesis makes it possible to explain a negative correlation between the skin temperature and the body mass index and a twofold increase in the oxygen uptake during acute cold exposure. Nevertheless, further investigations are necessary to clarify the physiological mechanisms underlying the significant correlation between skin temperatures at rest under thermoneutral conditions and the maximal aerobic capacity, anaerobic threshold and lactate accumulation after critical muscle load.