The purpose of this study was to evaluate perceived exertions for various levels of actual exertion. A total of 40 healthy adults participated. They repeatedly performed the task of exerting a grip force for 5 s, following the target force on a screen. Then, they were asked to evaluate the intensity of each task based on Borg's CR‐10 scale. The results of this study indicated that participants tend to underestimate their grip‐force exertion at low target‐force levels (10–40% maximum voluntary contraction [MVC]), whereas overestimation was found at high target‐force levels (60–80% MVC). Interestingly, perceived exertion was very accurate at a target‐force level of 50% MVC (the 50% phenomenon). Based on these results, regression equations were derived to estimate the actual exertion of grip force from a perceived exertion. The Borg's CR‐10 scale for grip force was revised based on the regression equations.
The results of this study could be used for hand function evaluation guidelines. In addition, this study could be used as a tool for physiotherapy to improve hand function and prevent its decline in elderly people.
Tasks involving the thumbs of workers are frequently carried out at industrial sites or in laboratories. This study measured thumb endurance time according to relative force levels in males and females. The experiment in this study involved 30 healthy participants (15 males and 15 females). Maximum thumb pressing force (MTPF) was measured and thumb endurance curves were developed using the measured thumb endurance time of participants’ dominant hand according to various force levels (10, 20, 40, 60, 80, and 100% MTPF). On the basis of the results, females demonstrated greater endurance time than males at 20% MTPF, and statistically significant differences according to gender are not shown at MTPF levels of 40% or higher. A rapid increase in endurance time was observed at low force levels. The findings of this study are expected to facilitate the establishment of appropriate working levels for the thumbs of workers in order to optimize work design. In this study, the effects of gender and target force level on thumb endurance time performance were evaluated. The findings of this study could provide valuable information for developing ergonomic guidelines of thumb pressing force tasks for the workers.
Cover Caption: The cover image is based on the Full Article Perceived level of exertion compared to actual grip force exertion: The 50% phenomenon by Kyeong‐Hee Choi et al., https://doi.org/10.1002/hfm.20808.
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