Effects of bi-axial ankle strengthening on muscle co-contraction during gait in chronic stroke patients: A randomized controlled pilot study

•Introduced comprehensive Ankle Movement Training(AMT) for stroke patients.•AMT improved ankle muscle strength and co-contraction during gait in stroke patients.•Emphasizing a significant consequence of AMT on gait recovery in stroke patients. Ankle dysfunction in patients with stroke is a common but serious cause of balance and gait impairments. However, comprehensive paretic ankle training seldom exists. Thus, we investigated the effects of a bi-axial ankle muscle training program using visual feedback as a means to improve ankle strength and performance of functional activities in patients with stroke. This study was a randomized controlled pilot trial with concealed allocation and assessor blinding and intention-to-treat analysis. Twenty-five patients with stroke and difficulty in walking (e.g., foot drop) or ankle muscle weakness receiving inpatient rehabilitation were included. The experimental group underwent ankle muscle training consisting of passive stretching, control of ankle muscles, and active-resistive strengthening using visual feedback for 40 min per day, 5 times per week for 4 weeks. The control group underwent ankle-related physical therapy, including ankle range-of-motion exercises. The amount of time for training was equal between the two groups. The outcome measurements were isometric ankle contraction force to assess the strength of ankle muscles, ankle proprioception, Fugl–Meyer lower extremity score, Berg balance scale score, walking speed, and ankle co-contraction index to assess muscle efficiency during gait. The analysis revealed significant between-group differences in the ankle muscle strength in each direction (P < 0.05), Fugl–Meyer score (P < 0.01), and stance-phase co-contraction index (P < 0.05). After training, the experimental group displayed significant within-group differences in the strength of the ankle muscles in each direction (P < 0.01), ankle proprioception (P < 0.05), and walking speed (P < 0.05). Our findings demonstrate the significant short-term effects of ankle muscle training on strength, walking speed, and muscle efficiency in patients with chronic stroke.