The effect of heat acclimation on the sweat lactate concentration vs. sweat rate relationship

It is well known that there is a high concentration of lactate in sweat. Interest in measuring sweat lactate has arisen from its potential role in several clinical and sport performance applications. However, the effect of heat acclimation on sweat lactate concentration is still under debate. This is partly because sweat lactate concentration is greatly affected by sweat rate, which is known to increase during heat acclimation. Thus, to better understand this issue it is necessary to account for sweat rate - which has not been done previously in the literature. Therefore, the purpose of the current study was to determine the effect of heat acclimation on the relationship between sweat rate vs. sweat lactate concentration. Six subjects completed a 7-day heat acclimation protocol. The daily 2-h exercise bout was split into three 40-min intervals with exercise intensity increasing with each successive interval. This was done to induce three different sweat rates to determine the sweat rate vs. sweat lactate concentration relationship before and after heat acclimation for each participant. A 2 (heat acclimation) x 3 (sweat rate) repeated measures ANOVA was conducted to determine statistical significance. There was a significant (p < 0.05) decrease in the grand mean sweat lactate concentration over the course of seven days of heat acclimation from 17.0 ± 5.0 to 11.3 ± 1.1 mmol/L (p < 0.05). A significant (p < 0.05) heat acclimation x sweat rate ordinal interaction was also found. The results of the current study show that heat acclimation significantly decreases the sweat lactate concentration. In addition, there was a significant ordinal interaction which suggests that the impact of sweat rate on sweat lactate concentration is decreased following heat acclimation.