A large amount of variation in limb length between terrestrial mammals has been observed. Increased limb length may have evolved as a mechanism to reduce the cost of transport (COT), allowing for energy allocation to other important functions. The relationship between energy expenditure and limb length was investigated at the population level in the Longshanks mouse. This unique line of mice has on average 13% longer tibia than a randomly bred Control line. The hypothesis that the Longshanks mice would have a lower COT and increased stride length was tested here. The results show that the Longshanks mice (N=19) did have a lower COT (-24%), a longer stride (+7%) and a lower stride frequency (-5-7%) when compared to the Control mice (N=22). The results provide support for a relationship between limb length and locomotor performance and form an important contribution to the understanding of selective pressures shaping limb length.