A comparison of sprinting kinematics on two types of treadmill and over-ground

Conventionally motorized treadmills elicit different sprinting kinematics to the over-ground condition. Treadmills powered by a torque motor have been used to assess sprinting power; yet, the kinematics of sprinting on the torque treadmill are unknown. This study compares the sprinting kinematics, during the constant velocity phase, between a conventional treadmill, a torque treadmill and the over-ground condition to assess the suitability of each treadmill for sprinting studies and training. After familiarization, 13 recreationally active males performed multiple sprints at various experimental settings on each surface. Ninety sprints, which attained mean velocities over 7.0 m/s, had their lower-body sagittal plane joint angles during ground contact captured at 250 Hz. These data were low-pass filtered at 10 Hz, and compared with respect to surface, subject and velocity using an ANCOVA statistical model. Sprinting on the conventional treadmill elicited a longer ground contact time, a longer braking phase, a more extended knee at foot strike and a faster extending hip than the torque treadmill and over-ground (all P<0.05). The torque treadmill obtained an equivalent sprinting technique to the over-ground condition, with the exception of a less extended hip at toe-off, suggesting that it is more appropriate for laboratory sprinting analyses and training than the conventional treadmill.