Purpose This study aimed to analyze the competitive demands of mountain running races of varying lengths. Methods Sixty-six male athletes competed in Vertical race (~3 km and ~1000 m of total elevation change), Sky race (~25 km and ~3000 m of total elevation change), and SkyUltra race (~80 km and ~9000 m of total elevation change). Exercise intensity and competition load (TL) were assessed using running power, heart rate, and rating of perceived exertion (RPE). Results The highest exercise intensity was observed in Vertical race (3.9 [0.4] W·kg-1, 93.6% [2.8%] HRmax, and 9.5 [0.7] RPE) compared to Sky race (3.5 [0.5] W·kg-1, 89.9% [2.4%] HRmax, and 8.5 [1.2] RPE), and SkyUltra (2.7 [0.6] W·kg-1, 73.4% [1.1%] HRmax, and 8.2 [1.1] RPE). Vertical races had the highest mean maximal power outputs for periods <10 minutes. They also had the highest proportion of time spent >5 W·kg-1 and the most time spent above the respiratory compensation threshold. The majority of time in SkyUltra was spent at low intensity. The highest TLs were observed in these races (6200.5 [708.0] kJ, 842.0 [35.7] AU for TLHR, and 4897.3 [940.7] AU for TLRPE). However, when normalized to competition time, the SkyUltra event showed the lowest values compared with the Vertical and Sky races (~11 vs ~14.5 kJ·min-1, ~1.5 vs ~2.5 AU·m-1 for TLHR). Conclusion The results of this study expand knowledge about the effort demands of mountain races and demonstrate how these demands are affected by race duration. Additionally, the study highlights the potential use of running power for quantifying exercise in this sport.
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