A wearable IMU-based method for measuring biomechanical parameters in hammer throwing
Introduction The development of a low-cost system for analysis of the hammer throw technique is presented. The system is based on analyzing the information provided by off-the-shelf inertial measurement units (IMUs). Methods Five Spanish national-level hammer throwers (2 women, 3 men) performed 6 trials with homologated implements (4 kg for women, 7.26 kg for men) at the High-Performance Sports Centre (CAR) in Madrid during regular training sessions. The IMUs were positioned at three points on the thrower’s body: right instep, lumbar zone, and wrist. All IMU raw data (angular velocities, linear accelerations, and Euler angles) were processed and visualized using Matlab software to analyze and derive additional parameters. Results After analyzing the patterns of the raw data provided by the IMUs with professional coaches, algorithms for determining the duration of the single and double support phases for each turn were developed and described in the paper. These raw data also allow us to derive additional biomechanical parameters that help characterize the quality of the athlete’s throwing technique (wrist angular velocity and linear acceleration, pelvic tilt, horizontal azimuthal angles, arm elevation angles, and vertical foot acceleration). Validation against a VICON motion capture system showed excellent agreement for phase durations (ICC = 0.977) and angular displacements (ICC = 0.976). Discussion The data obtained using IMUs represent only a subset of the information that can be obtained from a hammer throw using current 3D photogrammetry techniques. However, as the hammer throw is a rotatory movement, a valuable information according to the literature can be obtained from IMUs at very low cost and without access to specialized high-performance centers or biomechanics laboratories. These findings demonstrate that an IMU-based framework constitutes a reliable low-cost solution for coaches and athletes who can benefit from this technology in their regular training sessions.