Jump distance of dance landings influencing internal joint forces: I. Axial forces.

Knowledge of the magnitude and rate of applying axial forces (AF) during actual dance movements is necessary for understanding the etiology of chronic injuries and osteoarthritis. The purpose of this study was to investigate the effect of jumping distance on component ankle and knee joint AFs generated during the landing phase of traveling jumps. Six female dancers performed 10 jumps each at 30, 60, and 90% maximum jump distance (JD) and 15 jumps ranging from 35 to 100% JD. A sagittal view of the right leg landing onto a force platform was filmed. Greater ground reaction force maxima, knee flexion, knee and ankle flexion velocity, tibial landing angle, net ankle and knee joint moment maxima, ankle and knee joint reaction AFs, and quadriceps AFs (QuadAF) peak magnitudes and rates of AF application (dFmax/dt) were observed (P < 0.05) at increased JD. The QuadAF was a more important determinant of knee AF than joint reaction AF. Increased quadriceps force was useful for accommodating impact forces but served to increase its contribution to Knee AF, particularly during the later portion of the impact phase. High impact situations create significant magnitudes (e.g., 14 BW) and dFmax/dt of muscle AFs which could contribute to excessive joint wear.