| Summary: | 博士 === 高雄醫學大學 === 醫學研究所 === 91 === Objective
Accidental slips and falls in daily life, sports activity, or occupational environment can result in trauma and functional disability of the upper extremity. In order to treat and prevent these injuries, there is a need to further understand the loading mechanism of the upper extremity.
Methods
Three groups of young healthy males who were categorized by their abilities in performing push-up exercise volunteered for this investigation. Group one (NN) included 10 normal subjects with the average age of 24.6, the average body height of 169cm, and the average body weight of 61Kg. Group two (PN) included 10 rugby players with the average age of 16.4, the average body height of 171.2cm, and the average body weight of 67.2Kg. Group three (PT) included the same players from group two, who underwent two months of push-up training exercise.
In the first part of this study, a testing model was set up with motion analysis system (Motion Analysis Inc., Santa Rosa, CA, U.S.A.) and two force plates (Model 9281B, Kistler Instruments AG, Winterthur, Switzerland), to measure and analyze the loading biomechanics of the upper extremity during push-up exercise. The relationship between different hand position and upper extremity loading were studied.
In the second part of this study, a releasing system was added to simulate fall on the outstretched hand. Using a three-mass model, the relationship among different upper extremity postures and joint loading were analyzed. Furthermore, the effects of exercise training and fall strategy upon joint loading were investigated to evaluate their impact on fall prevention techniques.
Results
The results showed that the loading biomechanics of the upper extremity differed with various hand positions during the push-up exercise.
During fall on the outstretched hand, flexing the elbow at the moment of impact could reduce the first peak force F1, and delay the time of the second peak F2. This action resulted in a better spring and damping effect, and helped the upper extremity to absorb more shock.
The second peak force F2 was not significantly different among the three groups. However, group one (NN) had the highest F1, followed by group two (PN) and group three (PT), respectively. Time interval (Ts~T2 and Ts~Te) during the impact showed that PT > PN > NN. At T1, NN had the highest elbow joint force in the mediolateral and axial direction, followed by PN and PT, respectively. For shoulder joint loading at T1, NN had the highest axial force, followed by PN and PT, respectively. With different ability to absorb impact energy among the three groups, the results showed that PT > PN > NN. The three groups of subjects also used different initial elbow flexion angle at the moment of impact, showing that NN > PN > PT.
Conclusions
A biomechanical testing model for a simulated fall situation was developed in this study. Loading biomechanics among the three groups of subjects were shown to be different. Flexing the elbow at the moment of impact could reduce the risk of injury by producing a better spring and damper effect. Additionally, exercise training, such as push-up, could also be beneficial in reducing the first impact force.
The database established in this study will warrant a better understanding of the mechanism in the upper extremity trauma. This testing model will be helpful in designing protective devices for prevention of these injuries. Furthermore, these data will be valuable reference in clinical treatment and rehabilitation.
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