Upright human gait did not provide a major mechanical challenge for our ancestors

H.-M. Maus, S.W. Lipfert, M. Gross, J. Rummel, A. Seyfarth
2010 Nature Communications  
During human and animal locomotion, leg function can be described with simplified leg models, such a the bipedal spring-mass model. Here, it is assumed that the force produced by the leg during stance phase resembles that of a linear prismatic spring. This is a reasonable assumption for bouncing gaits like running and hopping and holds with some limitations also for human walking (at moderate speeds).
doi:10.1038/ncomms1073 pmid:20842191 fatcat:fcoknj4tr5eujdimosszrfoffm