Lactate-sweat relationships in younger and middle-aged men

Sweat lactate is at least partly derived from eccrine-gland metabolism. This study examined whether potential age-associated changes in sweat rate and skin blood flow influence sweat lactate. Six middle-aged(51.5 +/- 3.8 years) and 6 younger (25.8 +/- 1.5 years) men similar in VO2max, height, weight, percent body fat, and surface area completed constant-load (CON) cycling and interval-cycling (INT) trials. During each trial, sweat and blood were analyzed for lactate concentration at 15, 25, 35, 45, and 60 min. Sweat rates and estimated total lactate secretion were not significantly different (p > .05) between trials or groups. Blood-lactate concentrations were not significantly different between groups during CON but were significantly higher in younger men at 35 min and 45 min during INT. Sweat-lactate concentrations were not significantly different (p > .05) between groups during CON or INT. These results suggest that differences in eccrine-gland metabolism between young and middle-aged men are minimal.