INTRODUCTION: Cross-country skiing is a typical endurance sport with high reliance on maximal aerobic power. Nevertheless, improvements in performance by increasing muscle strength and power, especially in the upper body, has been reported. Also, anaerobic power is reckoned a determinant for cross-country performance, especially in sprint (Stöggl et al., 2007). From this, strength training should be beneficial for cross-country skiers. However, high volume endurance training may be antagonistic to strength training induced strength gain and may therefore not have any effect on cross-country performance. The present study aims at testing if heavy strength training affects muscle strength and cross-country ski performance in well trained skiers. METHOD: Subjects were 20 national level male and female cross country skiers and they were divided into a strength training group (ST group, 21.1 years, 179 cm, 73.6 kg, n=10) and a control group (CTR group, 21.7 years, 173 cm, 67.8 kg, n=10). Both groups continued their normal training for the early preparation period (May-August). In addition, the ST group performed heavy strength training (12 weeks). Strength training consisted of half squats, sitting pull-down, Standing pull-down (double poling imitation) and push-down and was performed twice a week. Strength training intensity ranged from 10 RM sets to 4 RM sets during the period and 3-4 sets were performed in each exercise. Before and after the 12-week intervention, the subjects were tested for muscle strength (half squat and sitting pull-down), 100 m sprint ski-skating performance, double poling performance on an ergometer (peak and mean power during a 20 s and 5 min all out lest) and performance in an uphill roller ski track in both skating and double poling. RESULTS: ST group increased 1 RM in half squat by 12±2% (p<0.01) and in sitting pull-down by 19±2% (p<0.01). No significant changes were observed in the CTR group. Jump height did not changed in the ST group (-0.9±2%) and was reduced by 6.2±3% (p=0.02) in the CTR group. Sprint time over 100 m ski-skating was not significantly changed in either group. Both the ST group (12±2%) and the CTR group (8±1%) increased performance in the double poling ergometer (both during the 20 s and the 5 min test), but there were no difference between groups. Both groups increased skating (3.5%) and double poling (6-8%) performance in the roller ski track with no significant differences between groups. DISCUSSION: The present study shows that muscle strength can be increased in well trained cross-country skiers during a high volume endurance training period. However, it is not clear from this study how this translates into ski performance since the increased strength did not have significant effects on ski specific tests. CONCLUSION: Muscle strength can be increased by heavy strength training in well trained cross-country skiers during a high volume endurance training period.
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