Dependence on exercise intensity of changes in electrolyte secretion from the skin sampled by a simple method

Secreta from the palm and forearm was sampled for 1-min periods by a new technique, using a glass cylinder. Subjects exercised for 10-min periods at successive intensities of 40%, 50% and 65% \(\dot V_{O_{2 max} } \) with a leg ergometer operated in the supine position. Changes in the concentrations (values) of Na⁺, K⁺ and Cl⁻ in their secreta during exercise were investigated. Significant positive correlations were found between the values of any two electrolytes in samples from the palm or the forearm, but the correlations between values for any one of the three electrolytes from the two sites were not significant. Values for concentrations of the electrolytes were significantly higher in samples from the palm than in those from the forearm at rest, 10 min after the beginning of exercise and at the end of exercise. No significant correlation was found between values for electrolytes in samples from the palm and the exercise intensity, but values for Na⁺ in samples from the forearm increased stepwise with increase in exercise intensity, and similar tendencies were observed for values of K⁺ and Cl⁻. The values for the three electrolytes in samples from the forearm, but not the palm, were significantly correlated with values for blood lactate, the percentage of \(\dot V_{O_{2 max} } \) and the heart rate. These results suggest that the present technique is suitable for successive samplings of secreta from the forearm, and that values for the electrolytes in samples are useful indices of exercise intensity.