16-2 Thursday, Jan. 5 10:15 - 10:30 Bending-stretching coupling in the human foot: Role of the transverse arch YAWAR, A*; KORPAS, LM; LUGO-BOLANOS, M; MANDRE, S; VENKADESAN, M; Yale University, New Haven, CT; Yale University, New Haven, CT; Brown University, Providence, RI; Brown University, Providence, RI; Yale University, New Haven, CT firstname.lastname@example.org
The human foot acts as an elastic interface between the body and ground, and must be sufficiently stiff to propel the body while still maintaining its form. Compared with healthy and arched human feet, the flat feet of those with collapsed arches or other primates such as the chimpanzee are softer and bend severely at the midfoot. Recent work hypothesizes that the transverse arch is the dominant contributor to the foot's stiffness ; two to three-fold higher than the contribution from the longitudinal arch and longitudinally oriented soft tissues including the plantar fascia. A key prediction of this hypothesis is that the distal metatarsal heads splay apart when the forefoot is loaded, and therefore greater stiffness of distal transverse ligaments implies greater foot stiffness. To test this, we experimentally estimated the foot stiffness of human subjects and quantified the effect of externally stiffening the distal metatarsal heads using elastic tape. Foot stiffness was estimated by applying external loads to bend the foot, and measuring the resultant deformation of the arch by tracking the height of the navicular. The estimated stiffness increases by a factor of 2.06±1.98 (mean ± std, N=7) upon reinforcing the metatarsal heads in the transverse direction using elastic tape. These results with healthy human subjects are the first direct evidence for the role of the transverse arch, and also suggest therapeutic strategies for humans that suffer from collapsed arches. 1. Mandre, S., M. Dias, D. Singh, M. M. Bandi, and M. Venkadesan. "Evolution of the transverse arch made the human foot stiffer." In Integrative and Comparative Biology, v56:E136. 2016.