Habitual energy expenditure of human climbing and clambering

Despite many studies on the energetics of terrestrial, aquatic and aerial locomotion, little work has been done on the costs of arboreal locomotion. There is increasing interest in modelling the bioenergetics of extinct mammalian species, including hominids, but as early hominids are thought to have combined terrestrial bipedalism with arboreal climbing and clambering, absence of data on the energetics of climbing in higher primates limits work on hominid locomotor energetics. In this study, the energetics of climbing and clambering in humans has been investigated to assess the differences in energetic cost between terrestrial bipedal walking and vertical climbing and clambering. Energy expenditure during climbing and clambering, walking and standing was measured in 29 active, non-obese young adults. Anthropometric data were also collected. Analysis using paired t-tests showed that there is a highly significant difference (p < 0.001) between mean walking and mean climbing and clambering expenditure, 24 +/- 7 versus 48 +/- 18 kJ/min respectively. Body mass, percentage body fat and fat-free mass were all positively correlated with energy expenditure. It was concluded that any energetic advantages that accrue from terrestrial bipedal locomotion may be offset by the great cost of arboreal activity, implying that the conditions under which bipedalism may have evolved were contingent upon the time allocation associated with arboreal and terrestrial locomotion.