Kinematics and performance on uphill and downhill trail running in elite and well-trained athletes

This study investigated the impact of uphill (UP) and downhill (DH) sections and their relative running gross kinematics on trail running performance in athletes with different competitive levels. Data were collected during the 2023 Dolomyths Skyrace (22 km, ± 1750 m elevation gain/loss). Split times for UP and DH sections were analyzed for the top100 male finishers. Running kinematics (stride duration, contact time, stride frequency, and stride length) was assessed via video analysis on four-course segments (two UP, two DH). Athletes were grouped by performance level, and ANCOVA was used to analyze kinematic differences. Athletes spent more time on UP (62.5 ± 1.3%) than DH (37.5 ± 1.3%), making UP the strongest predictor of overall time ( p  < 0.001). However, percentage time differences among runners were greater in DH, where time loss from the best split was higher (21.6 ± 0.3%) than in UP (18.5 ± 0.3%, p  < 0.001). The relationship between time loss and performance varied between sections ( p  < 0.001). Across race sections, speed decreased from elite to well-trained athletes, accompanied by longer CT and SD and lower SF and SL in both UP and DH ( p  < 0.001). After adjusting for speed, no significant group differences in kinematics remained ( p  > 0.05). In DH, SL and SD increased in the second segment. SF explained 38–39% of speed variability in UP, while SL explained 66–73% in DH. Between-group differences in DH performance exceed those in UP, significantly impacting trail-running outcomes and highlighting the need for targeted descent training. Kinematic variations were mainly driven by speed, with stride frequency driving ascent speed and stride length facilitating faster descents.