Validity and Reliability of Notch ® Inertial Sensors for Measure Elbow Joint Angle During Tennis Forehand at Different Sampling Frequencies.Validity and Reliability of Notch ® Inertial Sensors for Measure Elbow Joint Angle During Tennis Forehand at Different Sampling Frequencies

The aim was to determine the concurrent validity and the reliability of the NOTCH ® inertial sensors (IMUs) to measure elbow joint angle during tennis forehand at different sampling frequencies (100Hz, 250Hz and 500Hz), by comparing data with Optical-Motion-Capture-System (OS) in a sample of fifteen competition tennis players. The players performed the hitting test with IMUs and OS synchronized. The Root-Mean-Square-Error (RMSE) was tolerable (5° < RMSE ≤ 10) for all joint axis and sampling frequencies. Lin´s-Concordance-Correlation-Coefficient (LIN CCC) was very large (0.7–0.9) in all cases. The RMSE increased significantly (P > 0.05) in the recordings made at 100 Hz for the two planes of the elbow, with a large effect size (≥0.8). The within-subject variation of the RMSE and Lin CCC between test-retest showed that no significant differences were obtained in all the comparisons. Notch® is a valid and reliable tool to measure elbow joint angles during tennis forehand