Validity of a Commercially Available Inertial Measurement Unit for Vertical Jump Height Measurement

Abstract

3D motion capture (3D) systems are the gold standard for assessing displacement during movements such as a drop vertical jump (DVJ) and a countermovement jump (CMJ). However, it is not feasible to use 3D in the field during game or practice situations. URPOSE: To examine validity of vertical jump height measured by inertial measurement units (IMU). METHODS: Eleven male (15.4±0.9yrs, 178.0±6.5cm, 80.5±13.04kg) high school football players participated. A small IMU placed in an elastic belt was worn around the waist of each subject during 3 CMJ and DVJ trials. Maximum vertical jump height was recorded as the vertical displacement of the pelvis using standard 3D techniques. A 2X2 repeated measures ANOVA (p<0.05) was used to determine differences in vertical displacement between measurement methods and movement type. 95% limits of agreement (LOA) and Bland Altman plots were utilized to determine the level of agreement between IMU and 3D during each task. RESULTS: A significant interaction between measurement and movement was found in vertical displacement (p<0.05). During the CMJ, the displacement measurement was not different (3D: 46.9±5.4cm, IMU: 45.9±3.8cm p=0.36). However, during the DVJ, the IMU measurement was statistically underestimated (45.0±3.7cm p=0.001) compared to 3D (48.7±5.7cm). Bland Altman plots and 95% LOA (Figure) illustrate a systematic error between the IMU and 3D during the DVJ where jump height was underestimated by the IMU. Interestingly, during both tasks, agreement between measurement methods seem to increase at higher jump heights. CONCLUSIONS: IMU technology is advancing with potential utility for on-field and in-game use. However, the algorithms which calculate vertical jump height may need to be adapted for varying types of complex movements.Figure