Concurrent validity and reliability of torso-worn inertial measurement unit for jump power and height estimation

Abstract

The purpose of the present study was to evaluate the concurrent validity and test-retest repeatability of torso-worn IMU-derived power and jump height in a counter-movement jump test. Twenty-seven healthy recreationally active males (age, 21.9 [SD 2.0] y, height, 1.76 [0.7] m, mass, 73.7 [10.3] kg) wore an IMU and completed three counter-movement jumps a week apart. A force platform and a 3D motion analysis system were used to concurrently measure the jumps and subsequently derive power and jump height (based on take-off velocity and flight time). The IMU significantly overestimated power (mean difference = 7.3 W/kg; P < 0.001) compared to force-platform-derived power but good correspondence between methods was observed (Intra-class correlation coefficient [ICC] = 0.69). IMU-derived power exhibited good reliability (ICC = 0.67). Velocity-derived jump heights exhibited poorer concurrent validity (ICC = 0.72 to 0.78) and repeatability (ICC = 0.68) than flight-time-derived jump heights, which exhibited excellent validity (ICC = 0.93 to 0.96) and reliability (ICC = 0.91). Since jump height and power are closely related, and flight-time-derived jump height exhibits excellent concurrent validity and reliability, flight-time-derived jump height could provide a more desirable measure compared to power when assessing athletic performance in a counter-movement jump with IMUs.

Jump height from inertial recordings: A tutorial for a sports scientist

“…However, in-line with what has been reported by us 8,15 and by others, 17-20 significant mean bias with respect to jump mat-assessed jump height was observed between the methods when velocity extrema were used to determine the flight time to derive jump height (method "b"). Moreover, the limits of agreement were slightly narrower using method "a" compared with method "b".…”

“…sensors. 8,15,[17][18][19][20] Commercially available wearable sensors, inertial measurement units (IMU) in particular, have received recent interest. An IMU comprises an accelerometer and a gyroscope and many sensors also include a magnetometer (magneto-inertial measurement unit).…”

“…Moreover, jump height can be obtained from inertial recordings with multiple approaches, for example based on the flight-time and on the take-off velocity. 8,15,17,25 Therefore, a fully transparent, standardized approach to jump height estimation based on inertial recordings would arguably be desirable.…”

“…8,15 In practice, the best congruence between wearable inertial sensor-based jump height and jump height evaluated with force plates or motion capture have been reported based on flight time defined using the method "b" described above. 8,15,17 However, it is well-established that the velocity extrema-based timings (method "b") will produce an overestimate of the flight time due to the extrema occurring prior to takeoff (maximum velocity) and after touchdown (minimum velocity). 8,15,[17][18][19][20] Due to the noise caused by the movement of the sensor relative to the body during takeoff and landing, 8,29 it is challenging to utilize the acceleration trace-based flight-time method (method "a"), and this approach remains scarcely explored in the literature.…”

“…8,15,17 However, it is well-established that the velocity extrema-based timings (method "b") will produce an overestimate of the flight time due to the extrema occurring prior to takeoff (maximum velocity) and after touchdown (minimum velocity). 8,15,[17][18][19][20] Due to the noise caused by the movement of the sensor relative to the body during takeoff and landing, 8,29 it is challenging to utilize the acceleration trace-based flight-time method (method "a"), and this approach remains scarcely explored in the literature. Due to the one-to-one proportionality between acceleration and force, one might expect a smaller bias against a contact mat with this method compared to the velocity extrema method for determining flight time.…”