ABSTRACT
Objective To measure the angular velocity and perpendicular ground reaction force of the ankle joint under different heights with half-squat jumping in parachute training simulation,providing a reliable experiment basis for the preventing of ankle injury.Methods A total of 18 volunteers participated in this study.The experimental group included 9 male with experience of parachute landing,while the other 9 male without experience of parachute landing were assigned to the control group.Each subject was instructed to jump off a platform with a height of 30 cm and 60 cm and land on a hard surface in a half-squat posture.The dynamic landing process was recorded with a high speed camera and the biomechanical data was collected and analyzed,including perpendicular ground reaction force,angular displacement,velocity and acting time.Results From 30 cm's height,the ankle angular displacement of the control group was significantly larger than the experimental group (25.73°± 8.13° vs 20.05°± 12.27°,P ＜ 0.05).The perpendicular ground reaction force of the control group was significantly smaller than the experimental group (3 372.4±748.6 N vs 5 181.5±1 726.2 N,P ＜ 0.05).The acting time of the control group was significantly longer than the ex perimental group (0.049±0.015 s vs 0.012±0.004 s,P ＜ 0.05).The buffer time of the control group was significantly shorter than the experimental group (1.397±0.746 s vs 1.737±0.451 s,P ＜ 0.05).From 60 cm's height,the ankle angular velocity of the control group was significantly higher than the experimental group (25.45± 15.01 °/s vs 16.51 ±4.18 °/s,P ＜ 0.05).The perpendicular ground reaction force of the control group was significantly smaller than the experimental group (4 616.0±1 124.7 N vs 7 119.5±2 307.4 N,P ＜ 0.05).The acting time of the control group was significantly longer than the experimental group (0.048±0.013 s vs 0.015±0.006 s,P ＜ 0.05).The buffer time of the control group was significantly shorter than the experimental group (0.922±0.347 s vs 1.617±0.547 s,P ＜ 0.05).Conclusion Jumping from different heights,the experinental group was larger in perpendicular ground reaction force but smaller in the angular velocity and displacement than the control group.There was a shorter acting time and a longer buffer time in the experimental group than the control group.