Influence of low muscle temperature on muscle metabolism during intense dynamic exercise.

Eight males performed intense leg cycle exercise at a constant rate of work averaging 350 W, according to three different protocols: 1) "Cold exhaustive" exercise (initial muscle temperature (Tm) = 29 degrees C), 2) "Warm non-exhaustive" exercise (initial Tm = 34 degrees C) for the same period of time as in 1), and 3) "Warm exhaustive" (initial Tm = 34 degrees C). In five subjects the concentration of various muscle metabolites was determined before and immediately, 1 min, and 5 min after exercise. Blood lactate concentration was determined before and repeatedly after exercise. At low Tm maximal work time was considerably shorter for all subjects compared to normal Tm, 1.3 and 2.1 min, respectively. Comparing conditions 1) and 2) oxygen deficit and the decrease in ATP and CP content were the same in the two experiments. There was a significantly higher concentration of glucose-6-phosphate 17.6 +/- 10.1 and 8.0 +/- 6.2 mmol X kg dw-1, respectively, and a tendency to higher lactate concentration 60 +/- 36 and 33 +/- 14 mmol X kg dw-1, respectively, immediately after exercise in the "cold exhaustive exercise". Peak blood lactate concentration appeared significantly later after "cold exhaustive" exercise indicating a slower elimination rate of lactate from the muscle compared to "warm non-exhaustive" exercise. The reduction in performance observed at low Tm may partially be explained by an increased accumulation rate of lactate in four of five subjects.