Fast twitch fibres may predict anaerobic performance in both females and males.

The aim of the present study was to compare males and females with similar training backgrounds regarding the relationship between anaerobic performance and muscle characteristics and to test whether any of the analysed expressions of muscle characteristics could predict some of the difference in anaerobic performance between sexes. Subjects performed 30 s all-out sprints on a bicycle ergometer (Wingate test) and needle muscle biopsies were taken at rest. Peak and mean power were respectively 44% and 48% higher in males than in females. Activity of total lactate dehydrogenase (LD) was 33% higher and of M subunit of LD 38% higher in males. Anaerobic performance was directly related to the proportion of type II fibres, the relative M subunit activity or the activity of PFK in both males and females and the higher M subunit activity in males could predict some of the sex difference in anaerobic performance. It is suggested that anaerobic performance is directly related to fast contractile or/and anaerobic metabolic properties of skeletal muscle with no sex difference in this relationship. The difference in anaerobic performance between the sexes may partly be related to the sex difference in anaerobic metabolic properties of skeletal muscle.