THE STUDY OF KNEE JOINT FORCE AND TORQUE DURING STEPPING EXERCISE ON THE GROUND AND UNDERWATER

Step aerobic is a popular exercise in a fitness center. Unfortunately, stepping activities will bring lower-extremity stress and pain especially for stepping dancer in aerobic exercise (Hains et al., 1997). This study characterized the lower-extremity joint biomechanics associated with stepping activities in different environment. The impact forces on knee joint are important for walking, running and stepping in the lower-extremity, because it may cause knee joint injuries such as OA. Loading is also believed to play a role in the onset of OA (William et al., 2004). He found that the forces at the knee are considerably larger during stair climbing than during walking: the average resultant peak force during stair climbing is 5.4 times body weight (BW). Because of the decrease of the BW loading, former researchers agree that exercises underwater are better than those on the ground. Therefore, the purpose of this study is to identify the knee joint loading difference between ground and underwater stepping exercise. My hypotheses are 1) the knee force underwater is larger than on the ground during the up stepping position; 2) the knee force underwater is smaller than on the ground during the down stepping position