Sex Gap in Upper-Body Strength Widens with Age in Young Cross-Country Skiers

A new study of 98 competitive cross-country skiers and biathletes from the U16 to U23 age categories has found that the absolute performance gap between males and females in upper-body strength and double poling grows larger in the older age groups. The research, published in Frontiers in Physiology by a German-Norwegian team led by Carl-Maximilian Wagner of Leuphana University Lüneburg, examined how upper-body characteristics develop across adolescence and early adulthood in a sport where sex differences are known to be enlarged in techniques with a high upper-body contribution, such as double poling and G3 skating.

Little was previously known about how upper-body strength, aerobic power, and double poling performance develop across these age categories, and whether the gap between male and female athletes emerges gradually or is present from the start. To address this, the researchers recruited 47 male and 51 female competitive skiers and biathletes spanning the U16 to U23 categories. Each athlete completed a battery of laboratory tests: a 15-second double poling ergometer sprint to measure maximal upper-body power, an incremental double poling test to volitional exhaustion to determine peak double poling performance, one-repetition maximum tests in the bench press and bench pull to assess maximal upper-body strength, and a treadmill running test with poles to determine maximal oxygen uptake.

The results showed that males outperformed females on every performance measure, and that absolute values generally increased with age in both sexes. Statistical analysis revealed significant age-by-sex interactions for several key variables. The absolute one-repetition maximum in the bench pull (effect size η² = 0.13, p = 0.010) and bench press (η² = 0.12, p = 0.010), peak double poling power (η² = 0.14, p = 0.003), peak oxygen uptake during double poling (η² = 0.14, p = 0.003), and overall maximal oxygen uptake (η² = 0.11, p = 0.018) all showed interaction effects, indicating that the absolute gap between males and females was significantly larger in the older age groups.

The picture changed when the researchers normalized the measurements to body mass. For most body-mass adjusted measures, no significant age-by-sex interactions emerged, indicating that once differences in body size are accounted for, the relative sex differences remained largely stable across the age span. The one exception was peak oxygen uptake during double poling, which still showed a significant interaction after normalization (η² = 0.11, p = 0.019). No significant age-by-sex interaction was observed for the 15-second double poling sprint (η² = 0.05, p = 0.228).

Correlation analyses, controlling for age and sex, added a further layer of insight. Absolute maximal strength in the bench press and bench pull was moderately to strongly associated with the 15-second sprint power, peak double poling performance, and peak oxygen uptake during double poling, with correlation coefficients ranging from 0.50 to 0.61. When strength was normalized to body mass, these associations weakened considerably, dropping to between 0.13 and 0.39.

Aerobic power itself showed strong associations with peak double poling performance, with correlation coefficients between 0.73 and 0.82. This pattern suggests that both maximal upper-body strength and aerobic power are consistently linked to double poling capacity in young athletes, even after accounting for age and sex, highlighting the potential relevance of upper-body strength for double poling performance development in youth athletes.

The authors conclude that absolute sex differences in upper-body performance increase across age groups and are more pronounced than previously reported for lower-body performance in the same sport. However, the study’s cross-sectional design means that each age group was measured at a single point in time, so the observed age-related differences cannot be attributed specifically to maturation, training history, or other developmental factors.

For coaches and talent developers working with adolescent skiers and biathletes, the findings emphasize upper-body strength as a consistent correlate of double poling performance, while leaving open the question of how the widening absolute gap develops over time within individual athletes. Longitudinal follow-up studies would be needed to determine whether the age-group patterns reflect developmental trajectories and whether targeted training can influence them.

Subject of Research: Age- and sex-related differences in upper-body strength and double poling performance in adolescent cross-country skiers and biathletes

Article Title: Age-related widening of sex differences in upper-body strength and double poling performance in U16-U23 cross-country skiers and biathletes

Article References: Wagner, C.-M., Sandbakk, Ø., Schiemann, S., Röhrs, D., Schmidt, T., & Keiner, M. (2026). Age-related widening of sex differences in upper-body strength and double poling performance in U16-U23 cross-country skiers and biathletes. Frontiers in Physiology, 17, 1890471. https://doi.org/10.3389/fphys.2026.1890471

Image Credits: AI Generated

DOI: 10.3389/fphys.2026.1890471

Keywords: cross-country skiing, biathlon, double poling, upper-body strength, sex differences, adolescent athletes, aerobic power, VO2max, bench press, bench pull, exercise physiology, U16-U23