@Garrett Markle agreed mate - great book, and I think youβre right re: heel striking and running. I think the walking gait is a bit of a different beast, where the impacts are low (especially with good technique) and the efficiency gains are high. Anthropologically, gorillas are a fascinating study, as they develop heels more suited to walking / standing as they spend more time on the ground (whereas the gorillas in tree habitats still have a smaller highly mobile joint instead) https://biomedicalodyssey.blogs.hopkinsmedicine.org/2021/06/from-the-trees-to-the-ground-what-gorilla-feet-can-teach-us-about-evolution/