Comparing Two Training Frequencies of Dose-equivalent Hop-to-stabilization Balance Training on Sensorimotor Function and Plantar Biomechanics in Chronic Ankle Instability: a Randomized Controlled Trial

This study compares two progressive hop-to-stabilization balance (PHSB) training schedules with equal total training volume in people with chronic ankle instability (CAI). Current evidence supports the effectiveness of PHSB training for CAI rehabilitation, but no study has directly compared different training frequencies when total training dose is held constant.

Sixty participants with CAI were randomly assigned to three groups: a 4-week group (3 sessions per week, 12 sessions total, n=23), a 6-week group (2 sessions per week, 12 sessions total, n=22), and a waitlist control group (n=12). Each session lasted 20 minutes and followed the standardized PHSB protocol, including single-limb hops to stabilization, hops to stabilization and reach, unanticipated hop to stabilization, and single-limb stance activities with progressive difficulty. The control group received the intervention after study completion.

The primary outcomes are sensory organization measured by the Sensory Organization Test (composite score, six condition equilibrium scores, and four sensory ratios for somatosensory, visual, vestibular, and visual preference) and strategy analysis scores, and regional plantar pressure distribution during walking measured by FreeSTEP (peak force normalized to body weight across the first through fifth metatarsal heads, hallux, medial hindfoot, and lateral hindfoot).

Secondary outcomes include self-reported ankle function (Cumberland Ankle Instability Tool), dynamic balance (Y-Balance Test and side-hop test), static postural stability during single-leg stance measured by FreeSTEP (center of pressure mean velocity, confidence ellipse area, sway length, anteroposterior and mediolateral standard deviation of COP displacement, and Romberg index calculated as eyes-closed to eyes-open ratio of ellipse area), forefoot-rearfoot and medial-lateral plantar load ratios during walking, ankle range of motion measured by goniometer, and ankle muscle strength assessed by manual muscle testing.

This study aims to determine whether different training frequency schedules produce similar or distinct rehabilitation outcomes across sensorimotor, biomechanical, and patient-reported domains, providing evidence for flexible and individualized exercise prescription in CAI management.