Walking on the heel may have helped early humans walk further — study

The way people usually walk, with the heel striking the ground first, may be one of the key features of our bipedal gait. A study led by Nicholas Holowka of the University of Pennsylvania has shown that this type of gait requires significantly less energy than walking with the midfoot strike, but places a more abrupt impact load on the legs.

The paper was published on 8 September 2026 in the journal *Proceedings of the National Academy of Sciences*. The authors view this trade-off as a possible part of the evolution of endurance walking in hominins; however, the study did not directly measure the gait of extinct ancestors.

Details

In the laboratory phase of the study, the researchers compared the gaits of humans and chimpanzees using high-speed cameras and force platforms. Three adult male chimpanzees were observed on a track approximately 11 metres long whilst walking on all fours and on two limbs. The team also used data from a further three chimpanzees from a separate experiment and compared the results with two previously published datasets, which involved a total of 15 chimpanzees.

Twelve people took part in the human part of the study. Nine of them walked barefoot along a track approximately 7.6 metres long, fitted with force plates and reflective markers. The participants walked both in their usual manner and using a specially modified gait, in which they first placed the middle of the foot closer to the outer edge on the ground, followed by the heel. In addition, the researchers measured oxygen consumption and carbon dioxide output on a treadmill to assess energy expenditure.

During normal walking, all recorded human steps began with the heel. In chimpanzees, the position of the foot upon contact with the ground was much more variable, and when walking on two legs, they were less likely to use a heel strike. The range of foot-strike angles in chimpanzees was found to be 2.4–8.6 times wider than in humans.

For humans, heel-strike walking reduced the estimated metabolic cost by 26–41 per cent compared with midfoot-strike walking. At the same time, the rate of increase in impact load during a heel strike was up to 162 per cent higher. In chimpanzees walking on two legs, this figure for a heel strike was up to 138 per cent higher than for the gentler midfoot strike.

The authors suggest that the energy-saving benefits may have made long-distance walking more efficient, whilst thicker heel bones and larger lower-limb joints helped to compensate for the increased load. According to their hypothesis, this combination may have supported hunting and gathering strategies that required covering long distances on a daily basis.

Why this is important

The study shows that the uniqueness of human walking is not solely linked to an upright posture and straight legs. The very way the foot makes contact with the ground also differs from the gait of humans’ closest living relatives and provides a measurable energy advantage.

However, the evolutionary conclusion remains a hypothesis. The study was conducted on modern humans and chimpanzees in laboratory conditions, rather than on extinct hominins. The sample size of chimpanzees was small, and part of the comparison is based on previously collected data. Furthermore, the specially modified human gait does not fully replicate the natural gait of another species.

The authors note separately that modern hard surfaces may alter the balance between efficiency and impact load, but the effect of tarmac or other surfaces was not tested in this study. Nor does the study imply that normal heel-first walking should be avoided.

Source

Nicholas B. Holowka et al. Heel-strike mechanics reveal evolutionary trade-offs in hominin bipedalism. Proceedings of the National Academy of Sciences, 2026. DOI: 10.1073/pnas.2533918123.

Official Penn State press release: EurekAlert. The study was funded by the US National Science Foundation, the Leakey Foundation and the Wenner-Gren Foundation.