Gender differences in maximum voluntary lip-closing force during lip pursing in healthy young adults

The objectives of this study were to quantitatively evaluate the gender differences in the lip-closing force (LCF) generated during pursing-like lip-closing movement using a multidirectional LCF measurement system in healthy young adults. In 40 healthy subjects (20 women, 20 men; median age = 26·5 years, range = 22-41 years), LCF was recorded in eight directions during the performance of a voluntary pursing-like lip-closing task in four measurement sessions. The correlations between the total sum of the forces generated in all eight directions [total LCF (TLCF)] and each directional LCF (DLCF) and those between opposing DLCF were statistically analysed. The TLCF obtained from the highly reproducible measurements acquired in the four different sessions was normally distributed in both genders. The TLCF in men was significantly greater than that in women. Among the eight pairs of opposing DLCF, seven pairs of opposing DLCF showed significant correlations in men, while five pairs were significantly correlated in women. In men, no significant difference was observed between opposing DLCF; however, three pairs of opposing DLCF were significantly different in women. The present results quantitatively indicate that there are gender differences in the magnitude and directional specificity of the LCF produced during pursing-like lip-closing movement in healthy young adults.