Changes in the concentrations of Na+, K+ and Cl- in secretion from the skin during progressive increase in exercise intensity.

A simple method for sampling skin secretion in 1-min periods was developed for investigating the effects of progressive increases in exercise intensity on Na+, K+ and Cl- secretions from the skin of the forearm. Ten healthy male subjects performed exercise consisting of eight stepwise increases in intensity from 50 to 225 W, with a 25-W increase at each step. Exercise at each step was for 3 min followed by a 1-min recovery period. Samples of blood and skin secretion were taken during the recovery period. Significant positive correlations were found between the mean concentrations of Na+ and Cl- and between those of K+ and Cl- in the skin secretion. The concentrations of electrolytes in the skin secretion also showed significant correlations with the blood lactate concentrations. The inflection points for secretions of Na+, K+ and Cl- were 4.04, 3.61 and 3.83 mmol.l-1 of blood lactate; 64.42, 61.96 and 62.14% of maximal oxygen consumption (VO2max); and exercise intensities of 123.01, 117.65 and 125.07 W, respectively. No significant differences were observed between the value of 67.27% of VO2max or 134.00W at the onset of blood lactate accumulation (OBLA) and the inflection points. From these results we concluded that changes in electrolyte concentrations in skin secretion during incremental exercise according to this protocol were closely related with the change in the blood lactate concentration, and that the inflection points for electrolytes may have been near the exercise intensity at OBLA.