Losnegard, T., Mikkelsen, K., Ronnestad, B. R., Hallen, J., Rud, B., & Raastad, T. (2009). The effect of heavy strength training on muscle adaptations and performance in elite cross-country skiers. A paper presented at the 14th Annual Congress of the European College of Sport Science, Oslo, Norway, June 24-27.

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"Cross-country skiing is a typical endurance sport with high reliance on maximal aerobic power. However, the introduction of sprint skiing and mass start has increased the importance of other physiological factors affecting top speed on skies, such as muscular strength and the ability to generate high power. A good correlation has been reported between maximal power output measured in a 4 RM rollerboard test and sprint skiing tests in cross-country skiing. In addition to have a potential role on maximal power generation and top speed on skies, heavy strength training may also reduce the energy cost of skiing and thereby also affect endurance performance."

X-country skiers (M = 11; F = 8) were assigned to a strength training group (N = 9) and a control group (N = 10). In addition to regular training, the strength training group performed heavy strength training twice a week, for 12 weeks (3-4 x 4-10 RM sets in three exercises for upper-body muscles and one exercise for legs).

One repetition maximum (1 RM) improved in the strength training group in the sitting pull-down and half squat, while no changes were observed in the control group. Jump height decreased in the control group whereas there was no change in the strength training group. Small increases in cross sectional areas were found in the triceps brachii for both groups, with no change in quadriceps. VO2max in ski-skating increased in the strength training group, but was unchanged in running. Work economy, evaluated from VO2 during submaximal roller-skiing was unchanged and rollerski skating time-trial performance (~5 minutes) improved similarly in both groups. A 100-m sprint skiing test showed no significant changes in performance for either group. Correlation analyses at baseline showed a strong correlation between 1 RM sitting pull-down and time-trial performance and 1 RM half squat and 100-meter rollerski skating performance. However, there was no significant correlation between changes in 1 RM and changes in any of the performance tests.

Implication. A 12-week period of heavy strength training improved maximal strength in leg and upper body muscles, but had little effect on muscle cross sectional area in thigh muscles. In addition, heavy strength training added to regular endurance training improved VO2max during skating. However, despite physiological and specific factor changes there were no beneficial effects in time-trial performances. This is another example of changes being produced in strength training factors without any concomitant changes in actual sport performance. Thus, the strength training program produced changes in athletes that were irrelevant for the sporting performance, which was the justification of the program in the first place.

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