Effect of lumbar braces on spine flexion angular velocity and spine-pelvic angle during half-squat parachute landing

Objective To simulate half-squat parachute landing (HSPL) with different protective lumbar brace and analyze the effect of lumbar brace on spine flexion-extension movement. Methods In August 2016,30 male soldiers from paratroops army with average age of 22.79±3.73 years were enrolled,and they had simulated a half-squat parachute landing by wearing different protective measures (no-brace,elastic brace and semi-rigid brace) in this study.Every parachutist jumped off from height of 40cm and 120cm and landed on the platform in HSPL.The dynamic landing process was recorded with a Vicon motion capture system.Spine-pelvic angle (S-PA) and the spine flexion angular velocity (SFAV) were collected and analyzed. Results In terms of effect of wearing brace,at 40cm height,,wearing elastic-brace and semi-rigid brace leaded to significantly higher S-PA when compared with no brace (155.45±15.13° and 158.78±12.49° vs 146.01±16.19°,P<0.05),but no significant difference in spinal flexion angular velocity was found (211.68±13.29°/s,193.29±10.67°/s and222.53±11.75°/s,P>0.05);at 120cm height,the S-PA in the elastic-brace condition,the semi-rigid brace condition and the no brace condition differed significantly (153.66±8.79° and143.76±17.43° vs 133.84±13.73°,P<0.05),with significantly difference between each condition;While the spinal flexion angular velocity in the elastic brace condition and semi-rigid brace condition reduced significantly compared with no brace condition (290.12±14.73°/s and311.85±17.26°/s vs 389.94±23.40°/s,P<0.05,respectively),but there was no statistically significant difference between the former two braces (P>0.05).With an increase in height of jumping,the S-PA in different conditions decreased significantly and the SFAV in different conditions increased significantly (all P<0.05). Conclusion Our findings indicate that lumbar brace may limit lumbar flexion range of motion and reduce spine flexion angular velocity during landing.The semi-rigid brace is not superior to the elastic brace for change of SFAV,and the elastic brace is suitable for airborne troops.