| Summary: | 碩士 === 國立成功大學 === 生物醫學工程學系 === 103 === Cumulative trauma disorders of upper extremity, such as lateral epicondylitis, are common in sport activities and workplace. Inappropriate postures, repetitive movements and forceful exertions during tasks are risk factors. About 50% of novice tennis players are affected by lateral epicondylitis. This may be due to faulty mechanism of tennis backhand stroke in novices. Previous studies have investigated the effect of wrist angle on extension torque production. However, those information focused only on isometric and concentric contraction for wrist motions in sagittal plane. Furthermore, the available wrist dynamometers on the market provide wrist motions in sagittal or coronal plane, which are different from functional wrist activities in oblique plane. Besides that, there is also a lack of investigation about effect of wrist angle on wrist extensor activation.
In this study, performance of wrist extensors was compared between wrist motions in oblique and sagittal plane by using a custom made wrist dynamometer. The wrist motion simulated in oblique plane was tennis backhand stroke. The effect of wrist angle on torque production and muscle activation were examined during simulated tennis backhand stroke. Surface electromyography was used to record activation of wrist extensors during experimental tasks. Thirty healthy participants perform maximum isometric, concentric and eccentric wrist extension in oblique plane, and twelve of them also conducted the same tasks in sagittal plane. Wrist extension torque and activation of wrist extensors were both recorded during tasks.
The results showed that performance of wrist extensors was exactly different between wrist motions in oblique and sagittal plane, including muscle activation of wrist extensors during isometric contraction and peak torque magnitude and relationship between muscle activation and angular velocity during isokinetic contraction. About performance of wrist extensors in oblique plane, the wrist angle significantly affected extension torque and muscle activation during isometric contraction, whereas wrist angle interacted with angular velocity during dynamic contraction. Generally, the maximum wrist extension torque and neuromuscular efficiency occurred at wrist position of neutral and slight extension.
Results of this study can help to investigate cumulative trauma disorders of upper extremity. The custom made dynamometer used in current study provide wrist motions closer to functional wrist motions. This study can be further used in recommendations of tennis, muscle strength evaluation in the clinics and ergonomics of upper extremity. Future study about wrist joint is recommended to use modified dynamometer to investigate muscle performance which is closer to actual wrist motions. Further study is still necessary to confirm the relationship between wrist angle and forearm muscle performance.
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