Abstract
BACKGROUND: Exercise-based rehabilitation is the standard conservative treatment for Achilles tendinopathy, however, symptoms often persist post-treatment. Forefoot biasing footwear may augment rehabilitation by influencing tendon loading and ankle kinematics. This study aims to determine its effect on Achilles tendon loading and ankle kinematics in individuals with Achilles tendinopathy. METHODS: Fifteen participants with chronic symptomatic midportion Achilles tendinopathy (7 female; mean(SD) age: 39.5(6.4) years) performed seven commonly prescribed activities wearing only athletic shoes and with forefoot biasing footwear, in randomized order. Activities included walking and unilateral and bilateral heel raises and hops. Kinematics and kinetics were collected using computerized motion analysis. Achilles tendon force was estimated by dividing the ankle moment by an approximated tendon moment arm. Non-parametric statistical analyses assessed differences between footwear conditions (α = 0.05). FINDINGS: Forefoot biasing footwear significantly increased peak ankle dorsiflexion angle (range: 1.8-5.4 degrees) in all activities except unilateral hop, while reducing peak ankle plantarflexion angle (6.2-15.5 degrees) and ankle range of motion (1.8-10.6 degrees) with moderate to large effect sizes. Achilles tendon force impulse increased significantly (12 %-87 %) with forefoot biasing footwear in the five lowest peak loading activities, with large effect sizes. Walking showed consistent significant differences in tendon loading between footwear conditions (P ≤ 0.020). No significant differences in loading were observed between conditions for bilateral hopping (P ≥ 0.078). INTERPRETATION: Forefoot biasing footwear can modulate ankle angles and Achilles tendon loading in individuals with midportion Achilles tendinopathy and may be useful for progressing loading prior to introducing more advanced movements.