[Stress on the upper ankle joint in tennis-specific forms of movement]

The permanently increasing number of injuries in tennis, which are mainly located at the lower extremity, indicates that the internal load e.g. applicated to the ankle during certain movements might be a critical factor. In the present study the relationship between calculated ankle load and muscle forces appearing during tennis techniques performed in a laboratorial setup and some varying parameters such as playing surface, footwear and individual differences in movement structure were investigated. It could be shown that on a felt tennis floor due to its frictional characteristics the midfootstriking subject produced the highest ankle load, while the heelstriking technique reduces the load as well as the change of the playing surface to a floor with loose granulate. In addition it should be considered that external forces (e.g. gained from a force plate) must not be used as predictors for internal load. The presented data show that the model-aided load calculation (MALC) from two trials with similar ground reaction forces leads to completely different values of e.g. the ankle-joint force.