Running Up and Down Hills: Some Consequences of Size

TLDR

Small mammals can run at about the same maximum speed vertically as horizontally, but larger mammals cannot. Mice expend roughly eight times more energy per kilogram per meter than chimpanzees during level running, yet the additional energy cost of running uphill is only about one‑eighth as high for mice, and both species recover about 90 % of the uphill energy on the descent.

Abstract

Small mammals are able to run at about the same maximum speed vertically as horizontally, but larger mammals cannot do this. During level running a mouse weighing 30 grams uses about eight times as much energy per unit of body weight as does a chimpanzee weighing 17.5 kilograms (42.6 joules per kilogram meter versus 5.17 joules per kilogram meter). The additional energy required to lift 1 kilogram of body weight 1 meter while running uphill was similar for the two species (about 15.5 joules per kilogram meter). Therefore the increment in energy expenditure for mice to run uphill compared to running horizontally is about one-eighth that for a chimpanzee. Both mice and chimpanzees were able to recover about 90 percent of the energy stored running uphill on the way down.