Usefulness of Scissors with a Power-Support Mechanism to Assist Thumb Movement: An Observational Study

Kohei Koizumi,Yuji Koike,Akihisa Okino,Kazuhisa Takeda,Toyohiro Hamaguchi,Kumiko Sasao

doi:10.3390/app11167756

Abstract

Long-term repetitive movements, such as opening and closing scissors, increase strain on muscles and joints. Amplitude probability distribution function (APDF) analysis of surface electromyogram (sEMG) data was used to quantify the burden of muscle activity. We aimed to test the hypothesis that scissors with a power-support device assist repetitive thumb movements to reduce potential myoelectric activity. Twenty female university students who met the eligibility criteria performed a cutting experiment, with and without power-support device scissors. The primary outcome was a change in muscle load due to sEMG data that were analyzed using APDF, and the secondary outcomes investigated the occurrence of muscle fatigue and pain. The adductor pollicis muscle showed a significant decrease in muscle activity with power assistance. In addition, it was also found that fatigue and pain of the thumb and on the radial side of the forearm were significantly lower under the power-assisted conditions. The results of this study suggest that the assistive action of scissors with a power-support device compensate for muscle load on the thenar eminence. This may be used as a reference value to prevent the occurrence of hand disorders for hairdressers.

Highlights

This cross-sectional study compared the difference between power-supported scissors and non-power-supported scissors, using the muscle activity of the adductor pollicis muscle (ADP) and extensor carpi radialis muscle (ECR) as indicators
The reason for measuring the ECR was to confirm whether the dorsiflexion position of the wrist joint, which affects the movement of the thumb, is maintained
We investigated the myoelectric potential activity, subjective fatigue, and pain of the ECR whenthe power was assisted during scissors opening and

Summary

Introduction

During repeated occupational exertions, such as when a hairdresser is cutting with scissors, a burden is placed upon the bones, joints, muscles, tendons, ligaments, and peripheral nerves, which may cause musculoskeletal disorders, including tendonitis of the hand [1]. Upon analysis of hairdressers’ time spent performing duties, cutting with scissors predominates, taking up an average of 29% of the time [2]. The excessive repetitive movements involved in manipulating scissors for long periods are often associated with carpal tunnel syndrome (CTS) and De Quervain’s tenosynovitis [3,4]. Disorders due to overuse of the hands are common in occupations, such as hairdressers, that use scissors continuously for long periods [5,6], and hand disorders are a cause of hairdressers leaving the profession [7]

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