Muscle enzyme activities and fibre composition (m. vastus lateralis) and efficiency of the cardiorespiratory system in cross-country skiers.

Fourteen male cross-country skiers (class I and II, average age 20.5 years) were examined by biochemical and histochemical methods. The activity of selected enzymes of energy metabolism and the percentage ratio of different types of muscle fibres (m. vastus lateralis) were assessed. Furthermore, the maximum values of the cardiorespiratory system and post-loading pH and blood lactate were determined after performance on a treadmill. The mitochondrial enzyme activities were relatively high with a considerable scatter in the values of HOADH activity. The glycolytic enzyme activities were on the same level as in subjects not engaged in sports. The percentage composition of muscle fibres was as follows: FG - 7.56 %, FOG - 30.65 % and SO - 61.79 %. Oxygen consumption VO2 max.kg-1 was 67.44 ml.min-1, pulse oxygen 24.76 ml, post-load pH 7.24 and blood lactate concentration 6.98 mmol.l-1. There was positive correlation between CS enzyme activity and oxygen uptake (VO2 max), pulse oxygen and percentage of SO muscle fibres. The mean values found in the athletes examined in the present study corresponded to values of middle distance runners.