EFFECT OF NON-NEUTRAL POSTURES AND MOVEMENT TYPES OF THE WRIST ON MUSCLE ACTIVITY
Ardiyanto, Dr. Herianto
2014 | Tesis | S2 Teknik Industri-
This research examined the effect of non-neutral wrist postures and movement type of the wrist on muscle activity. Twenty one non-neutral postures were chosen from three extension angles (00, 250, and 500) and four ulnar deviation angles (00, 100, 200, and 300) which form the wrist during operation of computer input devices. Two types of wrist movements were investigated in this research: static and dynamic movement. Eighteen healthy males were participated in this research. The muscle activities were recorded using electromyography from two muscles in the forearm region: extensor digitorum (ED) and extensor carpi ulnaris (ECU). Then, the muscle activity expressed using 50th APDF and fatigue index. The results of this research shown that during static and dynamic movement, each of extension angles created significant differences on 50th APDF. Meanwhile, not all ulnar deviation angles created significant differences on 50th APDF. Significant differences of 50th APDF occurred when the wrist was positioned on 300 ulnar deviation angles. From the other muscle activity indicator, fatigue index, significant differences during static movement occurred between 00 and 250 extension angle. During dynamic movement, significant differences occurred between fatigue index on 250 and 500 extension angles. Then, the significant differences on fatigue index due to the effect of ulnar deviation angles variation only existed on 300 ulnar deviation angles. Moreover, the effect of type of movement also played an important role on the alteration of 50th APDF and fatigue index. Dynamic movement created significant higher 50th APDF and fatigue index on all muscles. Not only that, dynamic movement also changed the behavior of muscle activity increases compared to the static one. During static movement, the differences of muscle activity between every increase of extension angles were almost constant. While during dynamic movement, the differences were not constant. The difference between muscle activity on E25 and E50 was much higher than E25 and E50. In summary, although there were increases of muscle activities due to the nonneutral postures investigated in this research, not all non-neutral postures significantly affect the muscle activities. After that, type of movements played an important role on the development of muscle activity. Dynamic movement created a significantly higher muscle activity than static movement. In addition, type of movement also could change the behavior of muscle activity increases.
Kata Kunci : wrist, angles, movement, muscle activity
