PLOS ONE · Oct 21, 2026
Comparison of facial muscle activity between younger and older Japanese adults: A cross-sectional study
By Okamoto R, Adachi K, Mizukami K
A relationship has been reported between facial expressions and mental health. Surface electromyography (sEMG) is a standard modality used in clinical and psychosocial research to quantitatively assess facial muscle activity. However, limited information is currently available on age-associated differences in facial muscle activity. Therefore, we investigated facial muscle function by measuring activity during established voluntary facial movement tasks and comparing facial muscle activity between younger and older Japanese adults. This was a cross-sectional study that recruited participants using snowball sampling. The present results showed that during the neutral facial condition, older adults (N = 23; F: 19/ M: 4) exhibited significantly higher muscle activity than younger adults. In contrast, during other facial tasks, younger adults (N = 20; F: 9/ M: 11) showed significantly greater facial muscle activity. The increased muscle activity observed in the older group when expressing neutral facial expressions may be due to age-associated changes in muscle tone mediated by the sympathetic nervous system, similar to those observed in skeletal muscles. The decreased muscle activity during voluntary facial movements in the older group may also be related to aging.