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Electromyographic evaluation of perioral muscle activities during facial expression and button-pull exercise.

BACKGROUND
Muscle weakness negatively affects perioral muscles and quality of life. The button-pull exercise is used to teach lip closure (LC) and to strengthen muscles. However, how the muscles accomplish LC during button-pull and its training effect on each muscle are unknown.


OBJECTIVES
This study aimed to investigate the LC mechanism and the efficacy of perioral muscle training.


METHODS
Electromyographic (EMG) activities were obtained from perioral muscles along with the lip closing force (LCF), and were normalized to the maximum LC activities. Correlations between muscle activities and LCF were assessed during LCF increment/decrement task. The effectiveness of training methods was evaluated during functional face tasks (FFT). The effects of button-pull on muscles were evaluated during static loadings with two sized buttons.


RESULTS
The muscles were active during LC, and the amplitudes changed with the LCF. In FFT, the muscles were simultaneously active and the total activity was highest during the blowing task. In button-pull, maximum button-pulling forces (BPFs) were significantly larger with the large button (p = 0.0001). In the static loading task, muscle activities increased with increasing button load. However, the small button produced significantly greater EMG activity than the large button in most of the load (p < 0.005).


CONCLUSIONS
LC is accomplished by the cooperation of perioral muscles. In button-pull, a larger button requires a larger BPF, but a smaller button shows higher muscle activities. Face expression exercises compare favorably with button-pull. Forceful LC and blowing tasks may be effective and balanced training of the perioral muscles.