Ageing reduces fatigue during submaximal intermittent contractions, but the influence of intensity on this ageing effect in males and females is not clear. Younger males (n = 8; 23 ± 2 years), younger females (n = 8; 22 ± 1 years), older males (n = 8; 67 ± 5 years) and older females (n = 10; 64 ± 7 years) completed intermittent calf contractions at four submaximal intensities (30-70 %MVC) for up to 20 min. MVC was assessed during exercise at 30-60 s intervals and its linear rate of decline represented fatigue. Individual relationships between intensity and fatigue (%MVC min(-1)) were fitted to a biphasic function consisting of a linear and nonlinear component. There was no age × sex × intensity interaction for fatigue (3-way ANOVA, P = 0.46). However, there were significant interactive effects of age and sex on endurance at 70 %MVC, fatigue at 70 %MVC and the linear component of the intensity-fatigue relationship. Endurance was lower and fatigue and its linear component were greater (P < 0.05) in younger males compared with other groups, but not different between younger and older females. This suggests that there is an intensity-dependent effect of human ageing on fatigue during submaximal exercise that is specific to males.