Analysis of metabolites in sweat as a measure of physical condition

Sweet samples induced by heating, exhaustive exercise and endurance exercise, were collected from several healthy subjects. Analysis of the metabolites in sweat was performed using either amperometric biosensors, constructed from a dissolved oxygen sensor and immobilized enzyme membranes, or commercial ion-selective electrodes. The average concentrations of lactate and ammonium ion measured in sweat induced by exhaustive exercise were 115.8 and 90.5 mM respectively, 5.2 and 10.6 times higher than the results obtained from heat induced sweat. This contrasted with only a 2.0 and 3.0 fold increase following endurance exercise. The lactate concentration in sweat was found to be linearly related to the concentration of ammonium ion, with a slope of 1.07 ([ammonium ion]/[lactate], r = 0.996, lactate range of 16.1 to 110.3 mM). In view of these results, lactate and ammonium ion in sweat were shown to be related to an increase in anaerobic metabolism, involving the glycolysis pathway and purine nucleotide cycle (PNC). It was demonstrated that the analysis of both lactate and ammonium ion in sweat is an effective, non-invasive and convenient method for estimation of physical condition.