Interest of inertial measurement unit tool in the functional evaluation of ankle evertor muscles in trail running

This study aimed to investigate the interest of inertial measurement units (IMU) in the functional assessment of the ankle to identify sport specific adaptations and to determine whether a hilly run session affected balance control and ability in accelerating eversion and slowing down inversion movements. Thirteen well-trained trail runners and 12 cyclists completed ankle tests on a destabilized footwear device: one balance-control test and two dynamic inversion and eversion tests (involving eccentric, ECC and concentric, CONC muscle regimens, respectively). Kinematic data derived from IMU were automatically calculated as performance scores i) to compare trail runners and cyclists at rest, and ii) to determine the fatigue induced by hilly run (16 km, 400 D+) in trail runners. Both ECC and CONC scores derived from angular velocity of twenty repetitions (with threshold of 60°/s and 250°/s, respectively) during dynamic tests. Results showed higher ECC score (CV = 14.6%; p = 0.06; ES = moderate) and lower CONC score (CV = −33.8%; p < 0.01; ES = large) in trail runners than in cyclists. Furthermore, proprioception score decreased in response to the hilly run session (CV = −6.1%; p = 0.03; ES = moderate). Kinematic data emphasized sport specific adaptations in the ability to control eversion and inversion movements. This might suggest differences in evertor muscle strength characteristics. Decrement in the proprioception score highlighted the interest of using IMU in the assessment of acute fatigue induced by hilly run.