Epidemiological Investigation Of Accidental Injuries In Chinese Parachutists And Experimental Study On The Training Load With Electromyography

ObjectiveTo obtain the knowledge of airborne forces in parachuting injuries and possible risk factors for airborne during the parachuting and training to provide the scientific basis of injury prevention through a large-scale cross-sectional epidemiological investigation targeted a certain group of airborne forces.MethodsA cross-sectional study was conducted in paratrooper by cluster sampling and develping the questionare of parachuting injuries. The survey data were input into the computer software dBase databases. Non-complying questionnaires were removed according to the logic testing. Then chi-square test and multiple regression analysis were used with SAS9.0.ResultsThe rate of daily injury in parachute training was 60.7% with 28.9% in serious injury. In parachuting trainings, the overall incidence of injuries was 13.9/1000 second parachute or 24.5% if counted the number of people. The incidence of either injury or serious injury was significantly lower than that of the training (P<0.05).Year-Jumps was used to indicate the level of airborne exposure. Before the group in 63 Year-Jumps, the injury rate increased slightly in each group (19.0%-28.8%). However, the injury rate after 63 Year-Jumps began to rise significantly. Injury rate and cumulative risk showed certain dose-response relationship with the increase of exposure level.Overall upward trend of injury rates between the two groups was significant difference (P <0.05). In the group of more than 644 Year-Jumps, the injury rate has reached 40.9%.The incidence of acciential injury in terms of landing was 86.2%, with the incidence during leaving plane 7.6%, and the incidence on the air 6.3%.As to the external risk factors relating to parachuting, Uneven terrains, high wind speed, carrying weapons and the certain aircraft type were significantly related to injuries(P <0.05). These factors are likely to increase the risk of parachuting. On the other hand, temperature, protection equipments and doors had no significant effect on the injury accident. Regarding to individual factors, the soldiers Parachuting injury rate enhanced significantly with the body weight increasing (P<0.05). However, there was no significantly relationship between the body height and the injury rate.Both in the training group and parachuting group, the main damage was sprain. Comparison of training and parachuting, higher incidence of spain occurs in the training group with the higher actual proportion of fractures in the parachuting group, and the difference between two groups was significant (P<0.05). Parachuting injury occurred was significantly increased mixed (P<0.05). In addition, the injury of sprain and fracture at the same time enhanced significantly in the parachuting group (P<0.05).The enhancement of ankle injury caused by parachuting was significantly. The proportion of low back injury was at a quite high level as well, although no statistically significant difference was found.92.0% of all the parachutists appeared to be fatigue after land training. The injury rate of the fatigue parachutists was 62.6% in the training group, significantly higher than the group without fatigue. Moreover, the injury rate of paratroopers rose from 43.1% to 90.3% with the degree of fatigue deepen (P<0.05).Conclusions The incidence of injury in Chinese paratrooper's parachute and training was still at a quit high level in comparison to the developed conutries. Accounting for relationship between exposure and injury, as well as integrated service time and the training intensity between airborne, it seems to exist a critical point, suggesting that paratroopers who experienced more than 63 Year-jumps should be focused-group for injury prevention. Risk factors for injury were in order of:the uneven terrains> the high wind speed> a certain type of aircraft > carry weapons. Protective facilities have not exerted their necessary functions for preventing paratroopers form injury. As to soldiers' personal factors such as bodyweight and body height, only the body weight was directly related to the injury. The maximum allowable weight limits should also be developed as a screening indicator to examine airborne recruits. ObjectiveTo evaluate loads of muscles involved during jumping training and flying rings by surface electromyography (EMG), hoping to provide a theoretical guidance to prevent musculoskeletal injury.Methods50 volunteers in paratroopers participated in this study, followed by the assistance of staff. The subjects jumped from a height of 1 meter,1.5 meters,2 meters of the platform and 1.5 meters,2 meters flying rings respectively, simulating parachute landing position. Then real-time telemetry was conducted through the surface EMG records of the tibialis anterior, gastrocnemius, semitendinosus, biceps femoris, rectus femoris, rectus abdominis, erector spinae and trapezius muscle respectively. The individual EMG signal of resting position recorded from soldiers was taken as control. The EMG signal at the largest contraction of all muscles was measured prior to detection of the platform or the flying rings training, which was used to standardize the root mean square values of these two different trainings. MVE% and MF were adopted to analyse EMG changes of all muscles at different heights to evalutate the effect of either platform or flying rings training on the soldiers' loading strength.ResultsWith the hight of platform training increasing, the MVE% of each muscle was increased, and the difference was significant compared to the resting state (neutral position) (P<0.01). Among them, the respective MVE% of erector spinae, gastrocnemius, rectus femoris and biceps femoris was even over 100%. When jumping from the height of 1.5m, the gastrocnemius muscle has exceeded its maximum voluntary contraction. At the height of 1.0m, the respective MVE% of tibial anterior, trapezius and erector spinae was less than 70% with others higher than 70%.. There were significant differences of the percentage of maximum Voluntary Contraction Electromyography (MVE%) of erector spinae, quadriceps and gastrocnemius musc between the height of 1.0 m,1.5m,2.0m and the resting state(P<0.05). During the flying rings landing training, the MVE% of all muscles increased at the height of both 1.5m and 2.0 m, and the differences between resting state (neutral position) and each height level were significant (P<0.05). Among them, the respective MVE% of the erector spinae, gastrocnemius, rectus femoris and tibialis anterior muscle also exceeded 100%. At height of 1.5m, only the MVE% of trapezius muscle does not exceed 70%.With the the height of platform increasing, the value of MF also enhanced, which was not same in all cases. The MF of rectus abdominis and biceps femoris muscle increased at different height level, whereas the respective MF of tibialis anterior, rectus femoris, trapezius, erector spinae, semitendinosus and gastrocnemius muscles declined when the platform height was 2.0 m, which was higher than that of the resting state and there was significant difference compared with the previous two height levels. The MF of each muscle tested at different flying rings height was higher than that of the resting state. Among them, the respective MF of erector spinae, rectus abdominis, and gastrocnemius muscle declined at the height of 2.0m, and there was a significant difference compared to the other group at the height of 1.5 m. There were no significant differences between tibialis anterior muscle, trapezius, rectus femoris, biceps femoris and semitendinosus at two different heights. Only the MVE% of tibialis anterior muscle showed significant correlation to body weight(r= 0.96, P<0.050). The correlation coefficient between the MVE% of erector spinae, rectus muscles, rectus femoris, biceps femoris, semitendinosus, gastrocnemius muscle and the body weight ranged from 0.61 to 0.84. However, there was no significant relationship between the MVE% of trapezius and the body weight.ConclusionsThe load of muscle was at quite high level during the jumping training, especially at platform height over 1.5 m, which mostly exceeded the limit value. The erector spinae muscles, gastrocnemius, rectus femoris and biceps femoris were mainly affected. Tibialis anterior muscle, erector spinae, quadriceps and gastrocnemius play a main role in the maintenance of body posture in the flying rings training which has a greater impact on rectus femoris and easily causes the symptom of fatigue. There is positive correlation between the load of training and the body weight, suggesting that the standard limit value of body weight should be developed to be regarded as medical screening indicator for paratroopers' recruitment.