Ageing refers to a decline in individual performance with increasing age that ultimately leads to a reduction in organismal fitness. Although the physiological causes of ageing are likely diverse, a decrease in mitochondrial function may play a central role, as mitochondria generate over 90% of the energy used by eukaryotic cells. Despite support from human and laboratory studies, the effect of age on mitochondrial function, and the extent to which it may differ between males and females, has la