Abstract

Physically active young men (n = 23) were studied in terms of susceptibility to muscle fatigue. The monitored decrease in peak torque during repeated isokinetic knee extensions was used as an index for fatigue. Tissue specimens from m. vastus lateralis were obtained and analyzed for their relative distribution of muscle fiber types based on a histochemical staining procedure separating fibers into three categories due to different ATPase systems: ST (slow twitch), FTa (fast twitch), and FTb (fast twitch). In accordance with previousstudies, muscle fatigue was found to be related to the relative distribution of fibers. However, when considering the individual percentage of FTb fibers, the same correlation coefficients were demonstrated. In confirming with the different metabolic and vascular profiles of the two FT fiber subtypes, it is suggested that FTb fibers are most susceptible to fatigue while the FTa fibersrepresent an intermediate fiber type in this regard. Verf.-Referat