JUMP DISTANCE OF DANCE LANDINGS INFLUENCING INTERNAL JOINT FORCES .1.AXIAL FORCES

Knowledge of the magnitude and rate of applying axial forces (AF) duri ng 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 k nee joint AFs generated during the landing phase of traveling jumps. S ix female dancers performed 10 jumps each at 30, 60, and 90% maximum j ump 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. Greate r ground reaction force maxima, knee flexion, knee and ankle flexion v elocity, tibial landing angle, net ankle and knee joint moment maxima, ankle and knee joint reaction AFs, and quadriceps AFs (QuadAF) peak m agnitudes and rates of AF application (dF(max)/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 contributio n to Knee AF, particularly during the later portion of the impact phas e. High impact situations create significant magnitudes (e.g.,14 BW) a nd dF(max)/dt of muscle AFs which could contribute to excessive joint wear.