title: Gait changes in a line of mice artificially selected for longer limbs.
abstract: In legged terrestrial locomotion, the duration of stance phase, i.e., when limbs are in contact with the substrate, is positively correlated with limb length, and negatively correlated with the metabolic cost of transport. These relationships are well documented at the interspecific level, across a broad range of body sizes and travel speeds. However, such relationships are harder to evaluate within species (i.e., where natural selection operates), largely for practical reasons, including low population variance in limb length, and the presence of confounding factors such as body mass, or training. Here, we compared spatiotemporal kinematics of gait in Longshanks, a long-legged mouse line created through artificial selection, and in random-bred, mass-matched Control mice raised under identical conditions. We used a gait treadmill to test the hypothesis that Longshanks have longer stance phases and stride lengths, and decreased stride frequencies in both fore- and hind limbs, compared with Controls. Our results indicate that gait differs significantly between the two groups. Specifically, and as hypothesized, stance duration and stride length are 8-10% greater in Longshanks, while stride frequency is 8% lower than in Controls. However, there was no difference in the touch-down timing and sequence of the paws between the two lines. Taken together, these data suggest that, for a given speed, Longshanks mice take significantly fewer, longer steps to cover the same distance or running time compared to Controls, with important implications for other measures of variation among individuals in whole-organism performance, such as the metabolic cost of transport.
authors.affiliation: Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary , Calgary , Alberta , Canada.
authors.forename: Leah M
authors.initials: LM
authors.lastname: Sparrow
authors.affiliation: Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary , Calgary , Alberta , Canada.
authors.forename: Emily
authors.initials: E
authors.lastname: Pellatt
authors.affiliation: Cumming School of Medicine, University of Calgary , Calgary , Alberta , Canada.
authors.forename: Sabrina S
authors.initials: SS
authors.lastname: Yu
authors.affiliation: School of Anthropology, University of Arizona , Tucson , AZ , United States.
authors.forename: David A
authors.initials: DA
authors.lastname: Raichlen
authors.affiliation: Department of Anthropology, City University of New York, Hunter College , New York , NY , United States.
authors.forename: Herman
authors.initials: H
authors.lastname: Pontzer
authors.affiliation: Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada; McCaig Institute for Bone and Joint Health, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Campbell
authors.initials: C
authors.lastname: Rolian
keywords: Gait; Limb length; Longshanks; Stance; Stride length