Effects of emphasized plantarflexion stop and heel lift height on the plantarflexion resistive torque in healthy young adults wearing ankle foot orthoses

[Purpose] This study aimed to investigate the effects of plantarflexion stop angle and heel-lift height on peak plantarflexion resistive torque (PFRT) of ankle-foot orthoses (AFOs), including the first and second peaks observed during the loading response and pre-swing phases, respectively. [Participants and Methods] Thirty healthy adults wore AFOs with stiff plantarflexion stops (20 Nm/°) and walked at a comfortable speed. The plantarflexion stop angle was set under three conditions: 10° plantarflexion, 0°, and 10° dorsiflexion. Heel-lift height was tested under four conditions: no heel lift, 1 cm, 2 cm, and 3 cm. Depending on the results of Levene’s test, two-way analysis of variance or Welch’s analysis of variance was performed using weight-corrected first or second peak PFRT values as dependent variables and plantarflexion stop angle and heel-lift height as independent variables. [Results] Increasing the plantarflexion stop angle toward dorsiflexion and increasing heel-lift height resulted in higher first peak PFRT values (range: 0.08–0.69 Nm/kg across conditions). The plantarflexion stop angle also affected the second peak PFRT (range: 0.07–0.44 Nm/kg), whereas the effect of heel-lift height was limited. [Conclusion] This study demonstrates that plantarflexion stop angle and heel-lift height influence peak PFRT values in AFOs.