Comparative Research On Muscular Load In Pointing Device Operation

The development of Graphic User Interface (GUI) makes the usability of computer better,also makes mouse as important way that user transfer information to computer, but at thesame time, many studies show that the wide use of mouse is an important cause ofmusculoskeletal problem. Searching an excellent device to replace mouse for keeping highperformance and reducing trauma comes into people's attention. This research used trackingtask needed continuous and accurate control, and studied the operating error and error variation,taken sEMG of each muscle in operation to study muscular operation load, compared the operationcharacteristics of each pointing device and their effects to body.Three experiments were conducted in this research, factors of target route, wrist support andtarget velocity were taken into account in these experiments. In addition, after every task the subjectsassessed the body strain they perceived, the strain level was set from Borg-scale, then the relationshipwithin load, performance and subjective assessment were analyzed.Main findings of this research are as following:1. In the process of 3 pointing devices operation, lots of muscles' load weren't high. Many muscles'load were low, e.g.M.trapezius, M.deltoideus and M.brachioradialis, their action may be related mainlywith maintaining the static posture of the whole body, but these muscles' action were influenced by theoperation act also.2. In the process of 3 pointing device operation, action level of the main operation muscle was higher.The increase of parts muscles' action level was related with the character of operation act, e.g. for mouseoperation, in the routines which contained left-right action component M.extensor carpi ulnaris' MVE%was very high.3. Based on the sEMG, no-support would increase shoulder and upper limbs muscles' load in theprocess of mouse operation, increase shoulder muscles' load in the process of trackball operation, andfurther more, the influence to the former was bigger than to the later. No-support didn't have much influence to hand muscle. Regarding to the operation performance and subjecting exertion, to mouse,support was better than no-support, to 2 trackballs, support and no-support had littledifference.4. Action level of parts of muscles would increase as the increase of velocity in pointing deviceoperation, but the quantity was little, and many muscles didn't have this velocity effect (according to thedevice). However, subjective exertion increased along with the operation acceleration.5. The results of sEMG could explain the results of subjective exertion farther; they providedcomplementary analysis data to each other. Compositive consideration of performance, objective indexesand subjective indexes were very important to scientific evaluation6. According to multi-index, in general, the operation performance of mouse was better than 2trackballs', but this advantage was reduced in fine operation, and there was trend that subjective exertion ofmouse operation was higher than 2 trackballs'. The results of sEMG showed that load of shoulder(M.trapezius.) and upper limbs (M.deltoideus) were bigger in mouse operation than 2 trackballs', it wasmore obvious in no-support condition. In addition, bad posture (e.g. excessive ulnar deviation)happened more probably in mouse operation.