PURPOSE This study aimed to identify the lower limb muscle activity based on direction prediction presence or absence and gender during side cutting in healthy college students. METHODS The study participants included 14 healthy males and females (8 males; 6 females). All participants ran at full speed for a distance of 12m, and side-cutting was carried out at 45 degrees in a randomly indicated direction and in a fixed direction. Simultaneously, data regarding vastus medialis, vastus lateralis, semitendinosus, and biceps femoris muscle activity of the dominant leg were collected using an electromyography sensor, and data regarding vertical acceleration were collected using an inertial sensor attached to the pelvis. A sync webcam was used for obtaining the initial contact of side cutting and the stance period time. During the 10 milliseconds (pre-activation) prior to the initial contact and 50% of the stance phase (loading phase), vastus medialis, vastus lateralis, semitendinosus, and biceps femoris average muscle activity and hamstring to quadriceps ratio included as variables. RESULTS During the pre-activation and loading phase, the vastus medialis muscle activity of the male group was higher in the unexpected condition than in the expected condition. Furthermore, hamstring to quadriceps ratio was confirmed to be lower under unexpected condition compared to under expected condition during on loading phase. CONCLUSIONS The study results suggest that the risk of anterior cruciate ligament injury may increase with side cutting under unpredictable conditions. It is expected to provide useful information for identifying factors related to knee injury in the general population.
