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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 normalised 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 = .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 < .005)., Conclusion: 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 favourably with button-pull. Forceful LC and blowing tasks may be effective and balanced training of the perioral muscles., (© 2021 John Wiley & Sons Ltd.)

Objective: To test a novel sensor for assessing lip function., Methods: The electromyographic (EMG) activity of the upper orbicularis oris muscle (OOM), lip-closing pressure (LP) and intraoral baro-pressure (IP) were simultaneously recorded in 20 healthy subjects (10 women and 10 men) by using a novel composite sensor (CS). Subjects performed the lip-closure, blow and suck tasks. EMG activity of the upper and lower OOMs was recorded using conventional surface electrodes to evaluate the accuracy of CS electrodes. The subjects also rated the user-friendliness of the CS., Results: Integrated EMG signals recorded using the CS and conventional electrodes from the upper OOM were highly correlated (r = 0.77 ± 0.12 in women and r = 0.81 ± 0.10 in men). The signal-to-noise ratio was higher with the CS than with the conventional electrodes. The mean LP during maximum lip closure, blowing and sucking ranged between 2 and 6 kPa in women and between 5 and 7 kPa in men. The corresponding IPs in women were 0.0 ± 0.5, 3.2 ± 1.4 and -4.4 ± 2.6 kPa, respectively, and in men were -0.5 ± 1.4, 4.9 ± 1.8 and -5.6 ± 2.8 kPa, respectively. All subjects rated the recording technique as excellent or good., Conclusion: The CS was highly user-friendly and accurate in recording the EMG activity of the OOM and could simultaneously measure the LP and IP. Therefore, it could be an effective tool for evaluating lip function., (© 2019 John Wiley & Sons Ltd.)