INTRODUCTION Anterior cruciate ligament (ACL) injuries are commonly seen among athletes, which eventually makes more or less devastating impacts on their performances. Although ACL injuries may result from the knee collision, 70% of them are due to noncontact movements, including abrupt brakes, changing directions at high speed (i.e. sidestep cuttings and crossover cuttings). In doing so, one must at first have his or her axial foot fixed on the ground to absorb the momentum oriented from the original direction. Insufficient eccentric muscles or ligament strength are likely to trigger muscle and ligament injuries.