Effects of Unilateral Balance Training on Balance Abilities of the Untrained Leg in Healthy People and Patients With Musculoskeletal Disorders: A Systematic Review and Meta-Analysis

Unilateral balance training has been suggested to promote a cross-education effect, which consists of skills transfer from the trained to untrained leg thanks to spinal and supraspinal adaptations. This systematic review and meta-analysis aimed to investigate the effect of unilateral balance training on balance abilities of the untrained leg in healthy people and patients with motor impairments. A systematic search was carried out on MEDLINE, CENTRAL, EMBASE, Scopus, Web of Science, CINAHL and PEDro databases. Randomized controlled trials investigating unilateral balance training effects on static, reactive and proactive balance of the untrained leg in healthy adults or patients with musculoskeletal or neurological conditions were included. Methodological quality was assessed using RoB-2 tool and pooled or un-pooled results were reported as standardized mean difference with 95% confidence interval. Evidence certainty was rated using the GRADE approach. Ten studies were included. Unilateral balance training improved proactive balance of the untrained leg in healthy people (moderate evidence). Unilateral balance training of the unaffected leg enhanced static and proactive balance of the affected leg in patients after anterior cruciate ligament reconstruction (low evidence) and reactive balance of the affected leg in patients with chronic ankle instability (very low evidence). These findings supported the occurrence of a cross-education effect in healthy people and patients with musculoskeletal conditions of the lower limb. Evidence certainty is limited and further studies are needed.