LAUSR

BACKGROUND Parachutists are generally recognized as a "high-risk" group among military personnel. However, the findings came mostly from data analysis without soldiers as subjects. OBJECTIVE This study aimed to investigate the injury prevalence in Chinese paratroopers on-site and determine the relationship between injury and risk factors encountered during parachuting and land-based training. METHODS This study consisted of a field study with questionnaire and an experiment on muscle load during the simulated training exercise of platform jumping with surface electromyography (EMG), in which 7230 paratroopers and 38 soldiers were involved respectively. Chi-square test was used for the injury rate analysis, ANOVA and t-test for comparison of EMG data, and logistic regression for the analysis of multiple factors. Taking both intensity and time into consideration, jump-years (J-yrs) was used as a complex indicator for exposure to parachuting. Either injury per 1000 jumps or injured persons per 100 soldiers were calculated as injury prevalence. RESULTS The overall injury rate among Chinese parachutists was found to be 13.9 injuries per 1000 parachute jumps and 24.5% based on personnel. The person-based injury rate increased with the exposure level significantly (χ2 = 142.06, 2-sided, P < 0.05; trend test also significantly). Among the identified risk factors the uneven terrain was ranked as the most important one by logistic analysis. The EMG amplitude in MVE% increased with the platform height of all the 8 measured muscles and even reached 100% in 4 muscles, showing a high impact at landing. In addition, some characteristics of parachuting injury were also revealed by the injury type and site analysis. CONCLUSION A dose-response relationship between parachuting and injury was observed significantly in the survey of Chinese paratroopers. Their injury rate was found to be relatively higher than the reported internationally. Landing impact as a critical point for injury seemed to be proved by the investigation and also the experiment with EMG measurement. It is suggested for future studies, to use the person-based injury rate, landing studied in work physiology and with consideration of different landing skills.