Foot orthoses (FOs) are used to treat clinical conditions by altering the external forces applied to the foot and thereafter the forces of muscles and tendons. However, whether specific geometric design features of FOs affect muscle activation is unknown. The aim of this study was to investigate if medial heel wedging and increased medial arch height have different effects on the electromyography (EMG) amplitude of tibialis posterior, other muscles of the lower limb and the kinematics and kinetics at the rearfoot and ankle. Healthy participants (n = 19) walked in standardised shoes with i) a flat inlay; ii) a standard shape FOs, iii) standard FOs adjusted to incorporate a 6 mm increase in arch height, iv) and standard FOs adjusted to incorporate an 8° medial heel wedging and v) both the 6 mm increase in arch height and 8° increase in medial wedging. EMG was recorded from medial gastrocnemius, peroneus longus, tibialis anterior and in-dwelling tibialis posterior muscles. Motion and ground reaction force data were collected concurrently. Tibialis posterior EMG amplitude reduced in early stance with all FOs (ηp² = 0.23–1.16). Tibialis posterior EMG amplitude and external ankle eversion moment significantly reduced with FOs incorporating medial wedging. The concurrent reduction in external eversion moment and peak TP EMG amplitude in early stance with medial heel wedging demonstrates the potential for this specific FOs geometric feature to alter TP activation. Medial wedged FOs could facilitate tendon healing in tibialis posterior tendon dysfunction by reducing force going through the TP muscle tendon unit.

足部矫形器 (FO) 用于通过改变施加到足部的外力以及随后的肌肉和肌腱的力来治疗临床病症。然而，FO 的特定几何设计特征是否影响肌肉激活尚不清楚。本研究的目的是调查内侧足跟楔入和增加的内侧足弓高度是否对胫后肌、下肢其他肌肉的肌电图 (EMG) 幅度以及后足和脚踝的运动学和动力学有不同的影响。健康的参与者 (n = 19) 穿着标准化的鞋子，i) 有一个扁平的镶嵌物；ii) 标准形状的 FO，iii) 调整标准 FO 以将足弓高度增加 6 毫米，iv) 和标准 FO 调整为包含 8° 内侧足跟楔形和 v) 足弓高度增加 6 毫米和内侧楔形增加 8°。从内侧腓肠肌、腓骨长肌、胫前肌和胫骨后肌中记录肌电图。同时收集运动和地面反作用力数据。胫骨后肌 EMG 振幅在所有 FOs 的早期站立时均降低 (ηp²  = 0.23–1.16）。结合内侧楔入的 FOs 显着降低胫骨后肌电图振幅和外踝外翻力矩。早期站立时外侧外翻力矩和 TP EMG 峰值幅度的同时减少表明，这种特定的 FO 几何特征有可能改变 TP 激活。内侧楔形 FO 可以通过减少通过 TP 肌腱单位的力来促进胫骨后肌腱功能障碍的肌腱愈合。