Analysis of wheelchair rugby accelerations with fractal dimensions

The Hausdorff dimension and the average amplitude of the acceleration signal of a rugby wheelchair during a match quarter were calculated in order to determine which method is suitable for distinguishing between the different activities of a rugby wheelchair athlete. The activities were analysed on the match video and identified on the corresponding acceleration signal, measured with an Apple 4G iPod Touch which was connected to the frame of the wheelchair. The following activities were identified: collisions, high speed pushing, high speed coasting, low level activities, and no activity. The Hausdorff dimension values of high speed pushing and high speed coasting were similar. The average amplitude values of collisions and high speed pushing were similar, as were the values of high speed coasting and low level activities. Both methods combined provide a 2D map for distinguishing between all five activities, however, the standard deviation of the average amplitude is too high for clearly separating the activities on the amplitude scale.