Author(s): FEOFILAKTOV, V., Institution: RUSSIAN STATE UNIVERSITY OF PHYSICAL EDUCATION, Country: UNITED STATES, Abstract-ID: 156

INTRODUCTION:
Physiological and anthropometric adaptations to training have been well documented in elite senior cross-country skiers. In contrast, comparatively little is known about physiological profiles and seasonal adaptations in youth and junior skiers (XC), whose development is influenced by training exposure, biological maturation, and ongoing growth. Additionally, it remains unclear whether performance level influences adaptation during adolescence. Consequently, the aim of this study was to compare physiological and morphological profiles, as well as preparatory-period changes, between highly ranked junior and lower-ranked youth XC
METHODS:
Physiological and anthropometric profiles of 18 adolescent XC (14–18 years) were assessed at the beginning (May) and end (October) of the preparatory period following an extensive summer training program including roller skiing, running, bounding, strength training, and plyometrics. Group classification was based on results from the preceding winter season. Top performers (n = 7; 16.3 ± 1.1 years) placed within the top 5 at the Moscow Championships in the U16–U18 categories, whereas lower performers (n = 11; 14.3 ± 0.5 years) placed within the top 100 in the U14–U16 categories.
Laboratory testing comprised three domains: (1) Structural – seven anthropometric parameters; (2) Neuromuscular power – eleven strength and power variables; and (3) Metabolic – eleven upper- and full-body endurance parameters and three cardiovascular variables. Both absolute and relative values were analyzed to account for differences in body size and biological maturation. Differences within each domain were evaluated using mixed factorial MANOVAs.

RESULTS:
A significant main effect of time was observed, with most parameters improving in both groups (p < .05–.001). No significant time × group interactions were detected in any category, indicating similar adaptation patterns between groups. Large effect sizes were observed for strength and power (Ŋp2 = .911), endurance (Ŋp2= .363-.392),. body composition (Ŋp2 = .421), and morphology (Ŋp2 = .293). Significant main effects of group were identified for upper- and full-body endurance parameters, indicating superior performance in top-ranked juniors.
CONCLUSION:
Top-performing junior and lower-performing youth XC differed in absolute physiological and morphological levels, but not in their adaptive trajectories during the preparatory period. These differences were attenuated when expressed relative to body mass or body surface area. The greatest between-group differences in relative parameters were observed for lower- and upper-body peak power, cardiac output index, VO₂max, and VO₂peak. Importantly, the absence of time × group interactions indicates similar short-term adaptations between groups at this developmental stage. Because top performers were, on average, approximately two years older, the observed differences likely reflect a combination of training history, biological maturation, and performance level.