Lactate accumulation in muscle and blood during submaximal exercise.

Muscle and blood lactate concentration was studied in 10 healthy males during cycling exercise. For each subject the exercise intensity corresponding to a blood lactate concentration of 4 mmol.l-1 (OBLAw) was assessed by a step-wise increased exercise intensity protocol. In a second series of experiments the same protocol was performed but exercise was terminated at OBLAw and a muscle biopsy for subsequent analysis of lactate concentration was obtained from m. vastus lateralis. Biopsies were also taken at rest for histochemical determination of fiber type composition and capillary supply. The exercise intensity, which corresponded to OBLAw, averaged 159(117-216) W, equal to 65 (range 55-84)% of VO2max, and was found to be correlated to capillaries per fiber of the exercising muscle (r = 0.83, p less than 0.01). Muscle lactate concentration averaged 6.9 (range 2.1-12.6) mmol.kg-1 w.w. The change in blood lactate concentration (prior to and 1 min post exercise) was correlated to muscle lactate concentration (r = 0.71, p less than 0.05). It is concluded that great individual variations in the muscle/blood lactate gradient do exist during submaximal steady-state exercise, performed at a certain blood lactate level.