Effects of fatigue on kinematics and shock attenuation during downhill running

This study assessed the effects of a competitive trail run on running kinematics and shock attenuation in well-trained trail runners. Nine male runners performed a simulated short trail running race. Prior and 5-min after the race, participants completed a 290-m downhill run at pre-determined preferred speed. Inertial measurement units were used to assess selected kinematic parameters. The contact time showed a moderate increase in the fatigued condition (pre: 0.215 (0.024) s vs. post: 0.226 (0.219) s; p<0.01; d=0.51), whereas flight time was largely decreased (pre: 0.129 (0.027) s vs. post: 0.104 (0.026) s; p<0.01; d=0.94). There was a moderate decrease in the post-race for peak sacrum acceleration (pre: 56.9 (15.8) m/s2 vs. post: 49.1 (11.9) m/s2; p=0.038; d=0.56), while peak tibial acceleration and shock attenuation showed no change (p>0.05). These findings confirm that running-induced fatigue impacts running kinematics, although shock attenuation was unaltered with the present fatiguing protocol.