Muscle fatigue and its relation to lactate accumulation and LDH activity in man

Abstract

The lactate concentration in different muscle fiber types was determined in biopsy specimens from human vastus lateralis muscle after 30 and 60 s of maximal dynamic leg exercise. In addition, muscle fiber type distribution, total lactate dehydrogenase (LDH) activity and isozymes of LDH were determined. An increasing proportion of slow twitch (ST) fibers corresponded to better sustained muscle force. Lactate was found preferentially in fast twitch (FT) fibers after 30 s, but after 60 s, this difference was abolished. Differences between the 2 main muscle fiber types in muscle lactate, total LDH activity and M-LDH [muscle LDH] activity were correlated to muscle fatigue. Lactate or associated pH changes primarily in FT fibers could possibly be 1 factor responsible for the impaired muscle fucntion.