Energy cost of bipedal running
Fedak, M.A.; Pinshow, B.; Schmidt-Nielsen, K.
American Journal of Physiology 227(5): 1038-1044
1974
ISSN/ISBN: 0002-9513 PMID: 4440743 Document Number: 75608
The energy cost of running in two- and four-legged animals was compared. In 7 species of birds of bodyweights from 0.04 to 22 kg, steady state oxygen consumption during running on treadmills increased linearly with running speed. The slope (Erun) of the regression line was a constant for each species but smaller birds had a steeper slope than larger birds. Erun values for two-legged and four-legged runners were plotted on logarithmic coordinates against bodyweight fall along 2 different straight lines. Erun decreased more rapidly with bodyweight in four-legged than in two-legged runners. The lines crossed at about 1 kg bodyweight. For small body size (<100 g) the predicted cost of transport was significantly less for two-legged than for four-legged runners. For large body size (>5 kg) the opposite was true. For an animal the size of man, two-legged running is energetically over twice as expensive as four-legged running.