Objectives To compare age at key performance milestones between technical whole-body endurance sports and performance levels. Design Longitudinal big data analysis. Methods All top 30 swimmers, cross-country (XC) skiers and biathletes, who competed at the latest World championships (WC) were included and their ages at specific performance milestones (debut, first 17-30 rank, 9-16 rank, top 8) at junior (JWC) and adult WC were extracted from databases (719 women and 850 men). Athletes were divided into various performance levels based on their best individual ranking from adult competitions and compared using linear mixed model analysis. Results Only ~40% of the WC swimmers had competed in the JWC compared to ~90% of XC skiers and biathletes. Swimmers were, on average, 2 and 4 years younger at JWC and WC, respectively, than XC skiers and biathletes. In all three sports, there was an age gap (p<0.05) between the highest junior performance milestone and adult WC debut (3-4 years) but no age difference (p>0.05) between the performance milestones or performance levels at JWC. On average, female swimmers reached performance milestones one year earlier than their male counterparts, while there was no sex difference in XC skiing and biathlon. Conclusions The present findings encourage reassessment of sport-specific stereotypes regarding long-term athlete development. Although overall development patterns are similar between men and women, sex-specific training and competition planning is necessary at key junior career stages. Analyzing key structural elements of development systems across three technical whole-body endurance sports provides insights to develop future strategies for long-term athlete development.
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