To conduct a systematic review of existing literature of cross-education balance effects after unilateral training in the CAI population.

Data Sources

PubMed, SPORTDiscus, CINAHL Plus

Study Selection

To be included in the systematic review, studies were required to be published in English, include participants with chronic ankle instability, have participants undergo a unilateral therapeutic exercise for the lower extremity, and measure balance performance on the untrained lower extremity before and after the intervention.

Data Extraction

The certainty of evidence within each included study was assessed via the Downs and Black checklist. A score of 24–28 is “excellent” or “very low risk of bias,” 19–23 is “good” or “low risk of bias”, 14–18 is “fair” or “moderate risk of bias”, and less than 14 is “poor” or “high risk of bias.” We extracted information from each included study regarding their design, participant characteristics, inclusion criteria, independent and dependent variables, intervention, and results. Baseline and post-intervention balance performance data for participants' untrained limbs were used to calculate Hedge's g effect size and 95% confidence intervals.

Data Synthesis

Our search returned six studies that met the inclusion criteria. The articles' risk of bias ranged from high to low (11–19). Four of five studies that examined unilateral balance training reported a cross-education effect occurred. The lone study that examined resistance training at the ankle joint also reported a cross-education effect occurred. Several cross-education effects were associated with large effect sizes. This study was limited by a small number of studies that varied in methodology and quality.


The results of this systematic review suggest that unilateral therapeutic exercise can improve balance performance on the untrained limb of individuals with CAI. More work is needed to determine which training parameters are most effective for generating a cross-education effect.

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