Sweat lactate response between males with high and low aerobic fitness

Sweat lactate indirectly reflects eccrine gland metabolism. However the potential influence of aerobic fitness on sweat lactate is not well-understood. Six males with high aerobic fitness [peak oxygen consumption (V̇O₂peak): 61.6 (2.5) ml·kg⁻¹·min⁻¹] and seven males with low aerobic fitness [V̇O₂peak: 41.8 (6.4) ml·kg⁻¹·min⁻¹] completed a maximal exertion cycling trial followed on a different day by 60 min of cycling (60 rev·min⁻¹) in a 30°C wet bulb globe temperature environment. Intensity was individualized at 90% of the ventilatory threshold (V̇ _E/V̇O₂ increase with no concurrent V̇ _E/V̇CO₂ increase). Sweat samples were collected from the lumbar region every 10 min and analyzed for lactate concentration. Sweat rate (SR) was significantly greater (p<0.05) for subjects with a high [1445 (254) ml·h⁻¹] versus a low [1056 (261) ml·h⁻¹] fitness level. Also, estimated total lactate excretion (SR×mean sweat lactate concentration) was marginally greater (p=0.2) in highly fit males. However, repeated measures ANOVA showed no significant differences (p>0.05) between groups for sweat lactate concentration at any time point. Current results show highly fit (vs. low fitness level) males have a greater sweat rate which is consistent with previous literature. However aerobic fitness and subsequent variations in SR do not appear to influence sweat lactate concentrations in males.