Paper Title
COMPARISONS OF THE KINETICS OF SINGLE LEG COUNTERMOVEMENT JUMP IN HIGH-LEVEL SOCCER ATHLETES WITH LOWER LIMB INJURIES VERSUS THOSE WITHOUT

Abstract
Background/Aims - Soccer athletes use one leg as a supporting leg and the other as a kicking leg for training and competition. To maximize the use oflower limb strength, soccer athletes may develop lower limb laterality issues, further increasing the risk of injury. However, studies on laterality in soccer athletes with lower limb injuries and those withoutare limited. Therefore, the purpose was to identify the differences in the kinetics of single leg countermovement jump (SLCMJ) between soccer athletes with a history of lower limb injuries and those without. Methods - We recruited twenty-nine national level university soccer athletes (mean age: 20.00 ± 1.38 years). A questionnaire was used to collect basic parameters including age, height, weight, BMI, training hours daily, training days weekly, and lower limb injury in the past year. A force-plate (ELIGE T132CF) was used to collect the data (such as maximum power and velocity) of the SLCMJ test. Three tests of each leg were performed. The independent sample t test, paired sample t test, and non-parametric test were used for statistical analysis. Results - All the dominant foot of the participants were right foot. 15 participants experienced lower limb injuries were divided into injury group while 14 participants who had not experienced lower limb injuries were divided into injury-free group. Compared with the injury group, the mean maximum power of the right leg of the injury-free group was significantly greater during the SLCMJ test (injury-free group vsinjury group: 4235.74 ± 971.46W vs 3522.56 ± 1107.17W, p = 0.021). The injury group showed a significant difference in mean maximum jump velocity between the right and left legs (right leg vs left leg: 1.93 ± 0.12m/s vs 2.08 ± 0.15m/s; p = 0.004), while no such differences existed in the injury-free group. In the injury-free group, there were significant differences in mean maximum strength (right leg vs left leg: 2538.57 ± 480.176N vs 2180.29 ± 417.215N, p = 0.013) and mean maximum power (right leg vs left leg: 3626.26 ± 754.83W vs 3000.69 ± 594.15W, p = 0.006) between the right and left legs, while no such differences were found in the injury group. Conclusions - The lateralization of SLCMJ kinetics was significantly more pronounced in soccer athletes with lower limb injuries. A significant difference in the kinetic maximum power existed between the soccer athletes with lower limb injuries and those without. Lower limb injury might affect the maximum speed of jump. These findings could help coaches and athletes to develop lower limb function.