The greater power observed as a result of passively elevating muscle temperature prior to maximal sprint exercise may be due to a greater rate of ATP turnover (Edwards et al. 1972). Approximately 70-80% of the contribution to ATP turnover during short-term maximal exercise is a result of anaerobic metabolic pathways (Smith and Hill, 1991). The contribution to ATP turnover from glycolysis can be investigated by monitoring the blood lactate response to exercise. Therefore we investigated the effect of muscle temperature on the blood lactate response to the development of maximal power output on a cycle ergometer. Seven male subjects (mean ±S.E.M., age 25 ±2 years, body mass 69 ± 6kg) performed a 30 s maximal sprint on a friction loaded cycle ergometer on two seperate occasions. In the control muscle temperature condition subjects rested, standing up, for 30 min at normal room temperature (22±2°C). In the heated temperature condition muscle temperature was increased by immersing the legs up to the gluteal fold, in a water bath (42±1°C) for 30 minutes. Muscle temperature of the vastus lateralis was measured immediately prior to the sprint using a needle thermocouple. Venous blood samples were collected before, immediately, 2.5, 5, 10, 15, 20 and 30 minutes post exercise and analysed fluorimetrically for the concentration of blood lactate. Differences (P<0.05). between temperature conditions were evaluated using repeated measures ANOVA (2 – factor) and paired t tests where appropriate.Prior to exercise, the heated muscle temperature at depths of 3, 2 and 1cm were increased by 0.9, 1.4, and 1.9°C (P<0.05) respectively, in comparison to the control muscle temperatures. As expected maximal power output (corrected for flywheel acceleration, Lakomy, 1986) was greater when muscle temperature was elevated compared with control temperature (1127 ± 62 vs. 1029 ± 57 W respectively, P<0.05). In both temperature conditions the concentration of blood lactate following exercise increased (P<0.05) to between 8 and 9 mmol l¹ within 10 minutes and declined thereafter. There were, however, no differences between the two temperature conditions throughout the post-exercise period.These results demonstrate that in spite of a greater maximal power output when the exercising limbs were heated the blood lactate response did not differ.