Development of Lower-Limb Power Across Age and Sex in Junior and Elite Artistic Gymnasts

<b>Background</b>: Explosive and reactive strength of the lower extremities are essential performance determinants in artistic gymnastics. This study analyzed ten years of performance diagnostic data from Swiss junior and elite gymnasts to describe age- and sex-specific development patterns of lower-limb strength and to examine whether early strength levels predict later selection to the Swiss national elite team. <b>Methods</b>: Longitudinal performance data from 234 Swiss gymnasts (125 females, 109 males; 7-30 years) were analyzed. Explosive and reactive strength were assessed using countermovement, squat, single-leg, and drop jumps. Age- and sex-related differences, as well as associations with later national team selection, were examined. <b>Results</b>: Explosive and reactive strength increased significantly across age categories in both sexes (<i>p</i> < 0.001). In females, the greatest improvements occurred between U14 and U16 (explosive strength: +8.7-12.9%; reactive strength: +15.6-21.2%), followed by stagnation in explosive strength at older ages. In males, both strength qualities increased continuously from U14 to U18 (+9.3-15.7% per category; <i>p</i> < 0.001), with smaller gains at the elite level. Sex differences in explosive strength emerged from U16 and became pronounced from U18 onwards, favoring males (+11.3-19.2%). Reactive strength showed smaller and partly reversed sex differences, with females demonstrating higher values in U16 and elite athletes (up to +16.5%). Differences between athletes later selected for the national team and non-selected athletes were small and mostly non-significant. <b>Conclusions</b>: Lower-limb strength development in gymnastics follows distinct age- and sex-specific patterns. Systematic training appears to moderate sex-related differences, particularly in reactive strength. While physical capacities form an important foundation, technical proficiency seems to play a more decisive role in elite selection and long-term athlete development.