Does a Tailored Nine-week Training Intervention Improve Jump Height, Single-leg Stability, and Whole-body Stability Performance in Young Cross-country Skiers?

Abstract: The purpose of this study was to investigate if a nine-week training intervention composed of different mobility and stability exercises intending to improve jump height, whole-body stability, and single-leg stability of junior cross-country skiers. It was also of interest to see if the test equipment could determine the study participants' potential risk of injury with a built-in injury predictor measurement, Musculoskeletal Health (MSK).  A total of 16 cross-country skiers aged 16-20 years, 8 man and 8 women, performed the following tests on a force plate; Jump Scan (i.e., to characterize an individual's dynamic movement strategy), Plank Scan (i.e., to measure the individual's ability to control global static stability across each extremity), and Balance Scan (i.e., the individual's ability to maintain their center of mass over their center of pressure). After the initial scan, participants were assigned to the same nine-week intervention program, with Group 1 performing the program three times each week and Group 2 once each week before performing a post-intervention scan. Using two-way ANOVA showed no significant between-group differences. There was no significant difference when using three-way ANOVA within both intervention groups, except higher CMJ Load scores (p=0.032) and reduction in Plank scores, Plank Left (p=0.024) in male participants. When using logistic regression tests to determine the correlation between jump height (CMJ) outcomes effect on MSK injury risk between groups and within gender, a significant correlation in females was shown (p=0.0280, R=0.46). The present study's results suggest that a 9-week training intervention is not sufficient when training either one or three times per week for improving jump height, whole-body stability, and single-leg stability in junior cross-country skiers.