The need for superior performance in dance has impelled teachers and choreographers to use increasingly effective and sophisticated methods of preparation. To that end, such modalities ofbiomechanics as advanced motion-capture, muscle-function and muscle-strength techniques are being used to provide useful information about which of the dancers' needs require special attention. This often involves improving aspects of dance technique, which, in turn, may help dancers to prevent disabling injuries, the most frequent cause of notoriously short dance careers. Biomechanics may also help dancers to assess fitness levels, to control overtraining or "burnout," and assist them and their teachers in the effective scheduling of practice and exercise sessions.