## 4 Discussion  
In this study, we investigated the myoelectric potential activity, subjective fatigue, and pain of the ADP and ECR when power was assisted during scissors opening and closing movements using healthy women as subjects, and compared the differences with unassisted scissors. As a result, when using scissors with a power-support device, the active muscle units of the ADP were lower in static load level (P0.1), average load level (P0.5), and peak level (P0.9) than when using scissors without power assistance. There was no statistically significant difference in ECR muscle activity. Subjective fatigue and pain when using scissors with power support was lower than when using scissors without. These results support the hypothesis that scissors with a power-support device can reduce muscle fatigue and hand pain of the ADP during exertion. These findings may help hairdressers prevent the development of occupational diseases. However, as the subjects  
Figure 3: Comparison of muscle activity levels with and without power assistance, by plotting the probability of appearance of % maximal voluntary electrical activity (MVE) in the adductor pollicis muscle. (**A**) Amplitude probability distribution function (APDF) analysis plots of the adductor pollicis muscle (ADP) are shown, and muscle activity compared. (**B**) Amplitude probability distribution function analysis plots of the extensor carpi radialis (ECR) muscle are shown, and muscle activity compared. * \(p<0.05\). The polygonal line (on the left side of the A and B panels) represents the APDF value calculated from the surface electromyogram (sEMG) during scissors operation, and when the maximum pinch force was generated (y-axis, amplitude probability; x-axis, %MVE). Amplitude probability distribution function analysis shows the mean of the 10 th percentile, 50 th percentile, and 90 th percentile of %MVE. The yellow line indicates with assistance; blue line, without assistance; and the values of P0.9 were used to rearrange and display each in ascending order. The bar graphs (to the right of **A,B**) compare muscle activity at each percentile by assistance condition. Error bars show the mean standard error. within the study were not professionals, it remains necessary to verify whether a power-assist device can prevent hand disorders, such as CTS, for hairressers without interfering with cosmetology techniques. The results of this study showed that the average load level (P0.5) %MVE in the ADP while manipulating the scissors was 9.4 %MVE with assistance and 12.7 %MVE without assistance, and the muscle output was reduced to 10 %MVE or less by power assistance. The support mechanism of the power-support scissors is powered by the restoring force generated from the strain of the stretched wire, and assists the power of the lower blade of the scissors. In the preliminary experiment, the force to bring the lower blade closer to the upper blade was confirmed (0.81 N). [PERSON] et al. showed that assisting finger movement with wire tension can reduce sEMG muscle activity [23]. From these, and our, findings, it can be surmised that the restorative force of the steel wire used in the power-support device of the scissors decreased the burden on the muscles of the thumb. In addition, [PERSON] and [PERSON] measured electromyographic data while operating a touch screen with the thumb, and found that the muscle activity of the ADP muscle increased in the direction of addduction-abduction [24]. The opening and closing movement of the scissors in this study was a combined movement of the thumb, with the wrist fixed in dorsiflexion of about 30 degrees, accompanied by flexion-palmar abduction-palmar adduction. This movement is repeated adductor pollicis abduction, and it is speculated that scissors with a power-support device could effectively assist the muscle output of the ADP. Hairdressing involves repetitive tasks, and it has been reported that women's haircuts take an average of 51.4 min [3].