The effect of incline on sprint and bounding performance in cross-country skiers

Aim. Aim of the present study was to investigate performance and kinematics of cross-country skiers during sprint running and bounding on different inclines, in relationship to maximal strength, power and skiing performance. Methods. On day one, the maximal strength of 14 elite skiers was tested using a mid-thigh isometric pull and maximal relative leg power determined using squat and countermovement jumps. Day two involved 15-m maximal sprints and 5-step bounding at 0 degrees, 7.5 degrees and 15 degrees inclines. From video recordings sprint, step, contact and flight times; step length and frequency; total number of sprint steps and average bounding velocity were determined. Skiing performance was assessed using International Ski Federation (FIS) points from the preceding season and compared to strength, power, bounding and sprint performance, and kinematics. Results. On steeper inclines sprint time was higher and bounding distance shorter (both P<0.001), and step frequency during sprinting and bounding, reduced and increased respectively (P<0.001). Isometric maximal strength correlated strongly with bounding distance on the two steeper inclines (r=0.76 and 0.83). Squat and countermovement jump heights correlated moderately with sprint performance at both 7 degrees and 15 degrees, and bounding performance on all three inclines (r=0.55-0.65). The distance bounded uphill correlated moderately with FIS points (r=-0.55 and -0.67). Conclusion. Incline influenced sprinting and bounding performance and kinematics. Maximal leg power is important for both sprinting and bounding uphill, while maximal strength is important for the latter. The skiers with better FIS rankings bounded farther on steeper inclines, suggesting that this capacity is beneficial for cross-country skiing performance.