Evaluation of the Accuracy of Low Frame Rate Video in Kinovea® on Drop Jump by Interpolation

The aim of this study was to evaluate the accuracy of low frame rate video in 2D Kinovea® compared to 3D Qualisys Track Manager (QTM) on drop jump by interpolation. A total of 74 jumps were collected from 37 athletes. Reflective markers were placed on specific anatomical points (right/left upper point of acromion, anterior superior iliac spine, knee, foot) of the athletes. A single trial of a double-legged drop jumps were performed from two different box heights. QTM recorded all jumps using cameras at 500 Hz and synchronized with video at a speed of 30 Hz. All reflective markers were tracked and analysed in QTM and Kinovea. The horizontal and vertical positions of all reflective markers for jump instants (first contact, take-off, second contact) obtained both in QTM and the Kinovea, were exported to MS Excel. Kinovea data were interpolated to 500 Hz in Matlab software using a linear method. Horizontal and vertical displacement parameters were calculated in MS Excel, as the differences of the position data between the instants for the two different phases of the jumps (contact and flight phases). The Bland-Altman method was used for those parameters in JASP 0.17.1. The results showed significant agreement between QTM and Kinovea for the horizontal position parameters of left and right foot at first contact of drop jump. No significant agreement was found for the vertical displacement parameters during the contact and flight phases. In conclusion, to obtain accurate results in Kinovea, especially in the vertical displacement for a movement, it is recommended that the frame rate of the video should exceed more than 30 Hz.