Abstract

The effects of endurance training were studied in two groups of female cross-country skiers who differed in muscle fibre composition. The ST-group (n = 10) had 56-76 slow twitch (ST) muscle fibres and the FT-group (n = 10) 40-55 ST fibres in the m. vastus lateralis. During a four-month period, the subjects trained on the average 81 km per week. The intensive training averaged 8.5 km per week. The ST-group significantly increased their cycling maximum oxygen uptake (C max, 4.6) and the anaerobic threshold (AT, 2.8) during the training period whereas no significant changes were observed in the FT-group. Both the ST-group and the FT-group increased their skiwalking maximum oxygen uptake (S max), on average 8.7 and 3.8, respectively. In the ST-group, no significant correlations were found between training and the physiological parameters. In the FT-group, the amount of the total training and the intensive training correlated significantly with post-training S max, C max, AT, and the change in S max. The subjects possessing a higher percentage of ST fibres seemed to be able to increase their aerobic capacity more than those with a lower proportion of ST fibres. This latter group was probably forced to use fast twitch fibres during their training. The recruitment and adaptation of the fast twitch fibres may be responsible for the increasedmaximum oxygen uptake and anaerobic threshold in those FT-subjects whose quantity of training was high. Verf.-Referat