Effects of high and low blood lactate concentrations on sweat lactate response

Sweat lactate results from eccrine gland metabolism, however, the possible clearance of blood lactate through sweat has not been resolved. On separate days in an environmental chamber (32 degrees+/-1 degreesC) 12 subjects completed a constant load (CON) (30 min at 40% (V) over dotO(2) max) and an interval cycling trial (INT) (15 one-min intervals at 80% (V) over dot O-2 max, each separated by one min rest) each designed to elicit different blood lactate responses. Each 30 min cycling trial was preceded by 15 min warm-up (30 watts) and followed by 15 min passive rest. Sweat and blood were analyzed for lactate concentration at 15, 25, 35, 45, and 60 min during CON and INT. Total body water loss was used to calculate sweat rate (ml/hr). Blood lactate was significantly greater (p less than or equal to 0.05) at 25, 35, 45, and 60 min during INT compared to CON (similar to 5 mmol/L vs 1.5 mmol/L). Sweat lactate was not significantly different (p>0.05) between trials at any time (similar to 10 mmol/L). Sweat rates (similar to 600 ml/hr) and estimated total lactate secretion were not significantly different (CON vs. INT) (p>0.05). Elevated blood lactate was not associated with changes in sweat lactate concentration. Sweat lactate seems to originate in eccrine glands independent of blood lactate.