Comparing Two Training Frequencies of Balance Training for Chronic Ankle Instability

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.

Study Overview

• Status: Completed
• Conditions: Chronic Ankle Instability; Chronic Ankle Instability, CAI
• Intervention / Treatment: Behavioral: PHSB Training - High Frequency Short Duration; Behavioral: PHSB Training - Low Frequency Long Duration

• Study Type: Interventional
• Enrollment (Actual): 57
• Phase: Not Applicable

Contacts and Locations

Study Locations

• China
  • Beijing, China, 100084
    • Beijing Sport University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. History of at least one lateral ankle sprain with inflammatory signs (swelling, pain) and inability to bear weight on the affected side for at least one day after injury, per International Ankle Consortium criteria.
2. At least two episodes of giving way, recurrent ankle sprains, or perceived ankle instability within 6 months prior to enrollment.
3. Time since first ankle sprain greater than 12 months.
4. Time since most recent ankle sprain greater than 3 months.
5. No history of fracture or surgery in either lower extremity.
6. No other injuries causing inability to bear weight on either lower extremity within the past 3 months.
7. Cumberland Ankle Instability Tool (CAIT) score of 24 or below
8. Physically active: engaging in at least 30 minutes of moderate or higher intensity physical activity on at least 3 days per week.
9. Age 16-49 years.
10. Willing to provide written informed consent -

Exclusion Criteria:

1. History of lower extremity surgery or lower extremity fracture affecting lower limb function
2. Acute ankle sprain within 6 weeks prior to enrollment
3. Foot or ankle immobilization for more than 48 hours within the past 6 months
4. Neurological, vestibular, or other medical conditions affecting muscle strength or proprioceptive function
5. Currently receiving other rehabilitation treatment for the ankle -

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: 4-Week PHSB Training Group; Participants received progressive hop-to-stabilization balance training 3 times per week for 4 weeks (12 sessions total, 20 minutes per session). The training protocol included four components: single-limb stance activities with 7 progressive difficulty levels under eyes-open and eyes-closed conditions, single-limb hops to stabilization in four directions at three distances (45cm, 68cm, 91cm), hops to stabilization and reach with 7 progressive levels, and unanticipated hop to stabilization using a 9-grid system with 7 progressive levels. Training sessions were scheduled with approximately equal inter-session intervals (48-72 hours between sessions). n=23.	Behavioral: PHSB Training - High Frequency Short Duration; Standardized progressive hop-to-stabilization balance training performed 3 times per week for 4 weeks (12 sessions, 20 minutes per session, 240 minutes total). Training sessions were scheduled with approximately equal inter-session intervals (48-72 hours). The protocol consisted of four components with progressive difficulty levels: (1) single-limb stance activities under eyes-open and eyes-closed conditions on firm and foam surfaces with 7 levels, (2) single-limb hops to stabilization in four directions at three distances (45, 68, 91 cm) with 7 levels, (3) hops to stabilization and reach with 7 levels, and (4) unanticipated hop to stabilization using a numbered 9-grid system with 7 levels. Progression occurred when participants completed a level without errors. n=23.
Experimental: 6-Week PHSB Training Group; Participants received the same progressive hop-to-stabilization balance training protocol as the 4-week group, but at a frequency of 2 times per week for 6 weeks (12 sessions total, 20 minutes per session). Training content, progression criteria, and difficulty levels were identical to the 4-week group. Training sessions were scheduled with approximately equal inter-session intervals (72-96 hours between sessions).n=22.	Behavioral: PHSB Training - Low Frequency Long Duration; Identical progressive hop-to-stabilization balance training protocol as Intervention 1, performed 2 times per week for 6 weeks (12 sessions, 20 minutes per session, 240 minutes total). Training sessions were scheduled with approximately equal inter-session intervals (72-96 hours). Training content, progression criteria, difficulty levels, and exercise components were the same as the 4-week protocol. The only difference was the distribution of training sessions across a longer period at a lower weekly frequency. n=22.
No Intervention: Waitlist Control Group; Participants received no therapeutic intervention during the study period. Health education was provided during the waiting period. All control group participants were offered the PHSB training program upon completion of the study to ensure ethical treatment. n=12.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Cumberland Ankle Instability Tool (CAIT)	Self-reported ankle function questionnaire assessing perceived ankle instability during daily and sporting activities. Total score ranges 0-30, with higher scores indicating better ankle stability. A score below 24 indicates chronic ankle instability per International Ankle Consortium criteria. The minimal clinically important difference is 3 points. The Chinese version has demonstrated high internal consistency (Cronbach alpha 0.815) and test-retest reliability (ICC 0.99).	Baseline (within 1 week before intervention) and post-intervention (within 1 week after completion of the training program)
Y-Balance Test (YBT)	Dynamic balance assessment measuring maximum reach distance in three directions (anterior, posteromedial, posterolateral) during single-leg stance on the affected limb. Reach distances were normalized to limb length and expressed as percentage. Three trials per direction with the best value selected, and the average of three directions used as the final score. Higher scores indicate better dynamic balance.	Baseline (within 1 week before intervention) and post-intervention (within 1 week after completion of the training program)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
SOT Sensory Ratios	Four sensory ratios derived from the Sensory Organization Test: somatosensory ratio (Condition 2 / Condition 1), visual ratio (Condition 4 / Condition 1), vestibular ratio (Condition 5 / Condition 1), and visual preference ratio ((Condition 3 + Condition 6) / (Condition 2 + Condition 5)). Higher scores indicate better utilization of the corresponding sensory system for postural control. These ratios assess changes in sensory reweighting strategies following intervention.	Baseline and post-intervention (within 1 week after completion of the training program)
SOT Balance Performance	Composite equilibrium score (overall balance, range 0-100), individual equilibrium scores for each of the six Sensory Organization Test conditions (Condition 1 through Condition 6, each range 0-100), and strategy analysis scores indicating the relative use of ankle-dominant versus hip-dominant postural control strategies. Higher equilibrium and strategy scores indicate better balance performance. Assessed using a virtual dynamic balance testing system.	Baseline and post-intervention (within 1 week after completion of the training program)
Regional Plantar Pressure Distribution During Walking	Peak force normalized to body weight (PF/W, N/kg) at eight anatomical foot regions during level walking, measured by FreeSTEP system at 200 Hz sampling frequency: first through fifth metatarsal heads (M1-M5), hallux (T1), medial hindfoot (HM), and lateral hindfoot (HL). Data collected over 30 seconds of steady-state walking and averaged across 9 representative gait cycles. Changes in regional pressure distribution reflect altered foot loading patterns and ankle inversion tendency.	Baseline and post-intervention (within 1 week after completion of the training program)
Static Postural Stability Parameters During Single-Leg Stance	Center of pressure parameters during 10-second single-leg stance on the affected limb, measured by FreeSTEP system under both eyes-open and eyes-closed conditions: COP mean velocity (mm/s), confidence ellipse area (mm2), sway length (mm), and standard deviation of COP displacement in anteroposterior (SD-Y) and mediolateral (SD-X) directions. Three trials per condition with 60-second rest intervals, averaged for analysis. Lower values indicate better postural stability.	Baseline and post-intervention (within 1 week after completion of the training program)
Romberg Index	Ratio of eyes-closed to eyes-open postural stability parameters calculated from FreeSTEP single-leg stance data, including confidence ellipse area ratio, sway length ratio, and COP velocity ratio. Higher values indicate greater reliance on visual input for postural control. A decrease following intervention suggests reduced visual dependence and improved proprioceptive and vestibular contributions to balance.	Baseline and post-intervention (within 1 week after completion of the training program)
Plantar Load Distribution Ratios During Walking	Forefoot-to-rearfoot and medial-to-lateral plantar load distribution ratios (%) during walking, measured by FreeSTEP dynamic analysis. Changes in these ratios reflect shifts in overall foot loading strategy related to ankle inversion tendency in individuals with chronic ankle instability.	Baseline and post-intervention (within 1 week after completion of the training program)
Side-Hop Test	Timed functional performance test measuring the time required to complete 10 lateral hops over two lines spaced 30 cm apart on the affected limb, performed barefoot. Three trials with the best time recorded. Shorter completion time indicates better dynamic ankle function and neuromuscular control.	Baseline and post-intervention (within 1 week after completion of the training program)
Ankle Range of Motion	Active ankle joint range of motion measured by goniometer, including dorsiflexion, plantarflexion, inversion, and eversion of the affected ankle, recorded in degrees. Three trials per direction will be performed, and the maximum value will be used for analysis. This measure provides information on peripheral musculoskeletal adaptations following training.	Baseline and post-intervention (within 1 week after completion of the training program)
Ankle Muscle Strength	Isometric ankle muscle strength of dorsiflexors, plantarflexors, invertors, and evertors assessed using a hand-held dynamometer and recorded in Newtons. Three trials per direction will be performed, and the maximum value will be used for analysis. This measure provides information on peripheral musculoskeletal adaptations following training.	Baseline and post-intervention (within 1 week after completion of the training program)

Collaborators and Investigators

• Sponsor: University of Utah
• Collaborators: Beijing Sport University

Study record dates

Study Major Dates

• Study Start (Actual): November 8, 2023
• Primary Completion (Actual): January 17, 2025
• Study Completion (Actual): March 16, 2025

Study Registration Dates

• First Submitted: May 19, 2026
• First Submitted That Met QC Criteria: May 22, 2026
• First Posted (Actual): May 28, 2026

Study Record Updates

• Last Update Posted (Actual): May 28, 2026
• Last Update Submitted That Met QC Criteria: May 22, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: 2024034H

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No