Effects of lip-closing training on maximum voluntary lip-closing force during lip pursing in healthy young adults

To investigate the effect of lip-closing training, the time-course of multidirectional lip-closing forces during training was evaluated. The subjects were healthy young adults with no systemic disease. Ten subjects each were allocated to the training and non-training (control) groups. The subjects were instructed to use a lip muscle strength fixation device (M Patakara) for lip-closing training. Regarding closing the upper and lower lips against this force for 3 min as one task, the subjects were instructed to perform three tasks a day for 4 weeks. The multidirectional lip-closing forces were measured before, during and after training every week. In the control group, the forces were measured under the same schedule without training. After the initiation of training, the total lip-closing force significantly increased at 3 and 4 weeks in the training group compared with that in the control group (P = 0·003 at 3 weeks, P < 0·001 at 4 weeks). After the completion of training, the force decreased from 1 week and no significant difference from the control group was noted. When the lip-closing force was evaluated by direction, significant increases in the upward and downward directions were noted in the training group compared with those in the control group (P = 0·034 at 3 weeks for upwards; P = 0·027 at 4 weeks for downwards). Quantitative analysis confirmed that lip-closing training enhanced the lip-closing force regionally.