Tongue protrusion force and fatiguability in male and female subjects

Limb and respiratory muscle (diaphragm) strength and fatiguability have bee n extensively studied in man and are known to vary with age and sex. Howeve r, in contrast to limb muscles and the diaphragm, force and fatiguability c haracteristics have not been studied in upper airway muscles. This study examines the hypotheses that tongue protrusion strength or fatig uability, determined by the properties of the intrinsic muscles and geniogl ossus, may change with age and may be reduced in males compared to females. A force transducer was used to compare maximal tongue protrusion force (Fm ax) and fatiguability in 81 males and 86 females matched for age (mean+/-SD , 43+/-19 yrs, 42+/-19 yrs, respectively). Fatiguability indices were based an the time that subjects could maintain 50% of Fmax. Fmax declined with age in both males (r=-0.57, p<0.001) and females (r=-0.5 6, p<0.001). Fmax in males was greater than in females (males 26+/-8 N; fem ales 20+/-7 N; p<0.001). However, after correction of Fmax for sex differen ces in total body muscle (fat-free mass) there was no significant differenc e between males and females (p=0.3). There was also no difference in fatigu ability between males and females (p=0.5). In conclusion, tongue protrusion strength is greater in males compared to f emales, and decreases with age. If these differences also apply to patients with sleep apnoea, the reduction in maximal tongue protrusion force,vith a ge could be of relevance to the observed increase in prevalence and severit y of sleep apnoea-hypopnoea syndrome in middle age, but would not explain t he gender difference in prevalence.