Reductions in rearfoot eversion posture due to proximal muscle strengthening are dependent on foot-ankle varus alignment

Abstract

BackgroundStrengthening the hip and trunk muscles may decrease foot pronation in upright standing due to expected increases in hip passive torque and lower-limb external rotation. However, considering the increased pronation caused by a more varus foot-ankle alignment, subjects with more varus may experience smaller or no postural changes after strengthening. ObjectiveTo investigate the effects of hip and trunk muscle strengthening on lower-limb posture during upright standing and hip passive torque of women with more and less varus alignment. MethodsThis nonrandomized controlled experimental study included 50 young, able-bodied women. The intervention group (n = 25) performed hip and trunk muscle strengthening exercises, and the control group (n = 25) maintained their usual activities. Each group was split into two subgroups: those with more and less varus alignment. Hip, shank, and rearfoot-ankle posture and hip passive external rotation torque were evaluated. Mixed analyses of variance and preplanned contrasts were used to assess prepost changes and between-group differences (α = 0.05). ResultsThe less-varus subgroup of the intervention group had a reduced rearfoot eversion posture (P = 0.02). No significant changes were observed in the less-varus subgroup of the control group (P = 0.31). There were no significant differences in posture between the control and intervention groups when varus was not considered (P ≥ 0.06). The intervention group had increased hip passive torque (P = 0.001) compared to the control group, independent of varus alignment. ConclusionDespite the increases in hip passive torque, the rearfoot eversion posture was reduced only in women with a less-varus alignment. Having more foot-ankle varus may prevent eversion reductions.