## 4 Discussion
Additionally, correlations between wrist extensor muscle activity and finger tension have been reported [44]. These findings suggest that the increased antagonist muscle activity needed to stabilize the wrist in dorsiflexion may deplete thumb motor resources. The power-assist mechanism utilizes the restoring force generated by the deformation of a stretched wire, which was verified in preliminary experiments to provide approximately 0.81 N of force (moving the lower blade toward the upper blade). This restoring force likely helped maintain the skeletal muscle resources of the ADP, efficiently supplementing the thumb's function. This study involved novice operators using power-assisted scissors. Our research aligns with recent findings on the effectiveness of power-assisted scissors in reducing hand strain among hairdressers. In recent studies, researchers have measured the finger pressure on hairdressing scissor handles and found that ergonomically designed scissors reduce the rotational energy consumption of the blades [45]. This increases the efficiency of the thumb and other finger opposition movements, highlighting the reduction in force transmitted to the handles. As emphasized in recent guidelines for purchasing hairdressing scissors (_Why It's Important To Find The Right Shears, July 2024; Complete Guide To Hairdressing Scissors, July 2024_), minimizing finger load is crucial for mastering scissor operation techniques. The developed power-assist mechanism supports thumb function regardless of scissor shape, underscoring the importance of scissor shape selection and user-led task execution for injury prevention. This study had several limitations. First, the participants were female university students, none of whom were experienced scissor operators (i.e., licensed professionals). Future studies should include experienced operators, adjusting for years of employment and task duration. Second, we did not analyze the postures involved in scissor operation. Elbow and shoulder joint angles influence wrist positions and extrinsic finger muscles during scissor operations [46; 47]. Occupational MSD risk increases with prolonged exposure to specific postures [48]. Our study's short experimental duration (100 s) under constant posture conditions requires extended analysis, including postural control muscles of the fingers and upper limbs, to enhance the effectiveness of the power-assist mechanism. Third, we utilized general-shaped hairdressing scissors for simple opening/closing tasks without examining the effects of scissor type, opening angle, or specific techniques. Furthermore, the way information was presented to participants may have created an expectation bias favoring power-assisted scissors. Future studies should incorporate various scissors, cutting techniques, and adjusted task durations. Preventing MSDs requires evaluating job content, implementing preventive training, and mitigating risk factors [49]. Observational studies have identified upper limb disorder risks related to job characteristics in hairdressers [50; 51], but there are no established benchmarks for skills. Our study demonstrated muscle load and fatigue onset in novice scissor operators, providing a scientific basis for recommending appropriate joint movements. Additionally, MSD symptoms can often be alleviated by implementing job-specific evaluations and training programs [52]. Interventions in the workplace, such as ergonomic laws in California, have been effective in reducing back and neck pain [53]. Disseminating policies and guidelines that emphasize body management can enhance understanding of work-related burdens and alleviate symptoms [54]. Preventing MSDs in hairdressers requires creating employer guidelines based on skill benchmarks and implementing training regimens, to ensure that hairdressers can continue working healthily without compromising their motor functions.