A comparison of external plantar loading and in vivo local metatarsal deformation wearing two different military boots

The introduction of the M90 boot with a more flexible outer sole to military recruits in Sweden was accompanied by an increase in second metatarsal stress fractures. This study compared the new boot with the previous, stiffer model. A combination of external plantar pressure measurement (two subjects) and an in vivo measurement of dorsal metatarsal strain (six subjects) using strain gauge instrumented staples was implemented. Walking in both boot models resulted in increased plantar pressure under the heads of the lesser metatarsals and generally decreased loading under the remainder of the foot. Dorsal metatarsal tension increased for subjects wearing the new boot throughout a walking protocol.