How do the effects of an 8-week intervention influence subsequent performance development in cross-country skiers?

Author's accepted version (postprint).This is an Accepted Manuscript of an article published by Human Kinetics in International Journal of Sports Physiology and Performance (IJSPP) on 7/2/22.Available online: doi.org/10.1123/ijspp.2021-0356Purpose: To investigate how the effects of increased low- vs. high-intensity endurance training in an 8-week intervention influenced the subsequent development of performance and physiological indices in cross-country skiers. Methods: Forty-four (32 men and 14 women) junior cross-country skiers were randomly assigned into a low- (LITG, n=20) or high-intensity training group (HITG, n=24) for an 8-week intervention followed by 5 weeks of standardized training with similar intensity distribution, and thereafter 14 weeks of self-chosen training. Performance and physiological indices in running and roller-ski skating were determined pre-intervention, after the intervention (POST-1), and after the standardized training period (POST-2). Roller-ski skating was also tested after the period of self-chosen training. Results: No between-group changes from pre-intervention to POST-2 were found in peak speed when incremental running and roller-ski skating (P=0.83 and 0.51), although performance in both modes was improved in LITG (2.4% [4.6%] and 3.3% [3.3%], P<0.05) and in roller-ski skating for HITG (2.6% [3.1%], P<0.01). While improvements in VO2max running and VO2peak roller-ski skating were greater in HITG than LITG from pre-intervention to POST-1, no between-group differences were found from pre-intervention to POST-2 (P=0.50 and 0.46), although VO2peak roller-ski-skating significantly improved within HITG (5.7% [7.0%], P<0.01). No changes neither within nor between groups were found after the period of self-chosen training. Conclusions: Differences in adaptations elicited by a short-term intervention focusing on low- vs. high-intensity endurance training had little or no effects on the subsequent development of performance or physiological indices following a period of standardized training in cross-country skiers.acceptedVersio