Three-dimensional motion analysis using a system of 3 video cameras with a sampling of 60 fields/s was performed during the competition of 540 o Dwihuryeochagi. Motions were divided into five events: pivot foot landing (E1), pivot foot toe off (E2), COM max height (E3), kick impact (E4) and landing (E5). At E1, the stride width was greater for S than for F (p<.05) while the time was greater for S than for F during P4 (p<.05). At E4, knee angle was greater for S than for F (p<.05). At E5, hip angle was greater for S than for F (p<.05) while kick distance was greater for S than for F (p<.05). Furthermore, at P3, the time would be related to kicking velocity (p<.05), while at P4, the time, range of hip angle and knee angle would be related to kick distance (p<.05). At P1, COM horizontal velocity would be related to COM vertical velocity of P1 and P2 (p<.05). Based on the findings, success factors of 540°ý Dwihuryeochagi were COM horizontal velocity of P1, COM vertical velocity of P2, the time, kick distance, velocity, angle of lower extremities and coordination of P3-P4.

Sports injuries occur frequently during various sports competitions, and many studies have been conducted to improve athletic performance and prevent injuries (Mcnitt-Gray, 1989). Lower extremity joint injuries occur in approximately 77% of cases, with knee (21%) and ankle (18%) joint injuries accounting for significant portions of such injuries (Tropp, Askling & Gillquist, 1985). With respect to injury type, approximately 50% and 13% of all knee injuries involved the anterior cruciate ligament (ACL) and medial collateral ligament (MCL), respectively (Majewski, Susanneet & Klaus, 2006). Among the injury types, ACL injuries account for approximately 70% of non-contact injuries during actual physical activities (Meyer & Haut, 2008). Ankle injuries occur at a frequency of 50% for sprains, 17% for spasms, 12% for bruises, and 5% for fractures (Hang, 2013). Among athletes who incurred ankle sprains, >70% experienced additional and repetitive symptoms of dysfunction and re-injury (Anandacoomarasamy & Barnsley, 2005). Knee ligament injuries and ankle sprains occur during sports competitions and trainings (Hootman, Dick & Agel, 2007).Various reports have indicated that the causes of injuries include decreased range of motion (ROM) of the lower extremity joints and