Are Asymmetry-Focused Training Interventions More Effective than General Programs in Reducing Interlimb Asymmetries...

Interlimb asymmetries (ILA) have been associated with an increased risk of injury and decreased athletic performance. However, despite the growing number of training interventions targeting ILA, their comparative effectiveness relative to general strength and conditioning approaches has not yet been systematically reviewed.

This systematic review aimed to compare the effectiveness of asymmetry-focused training interventions versus general training programs in reducing ILA and improving physical performance in athletic populations. Specifically, it sought to compare individualized training programs that first identify the weaker limb during pre-testing and subsequently prescribe a greater training stimulus to that limb with general training protocols that apply the same training stimulus to both limbs, as well as unilateral approaches with bilateral training strategies.

Following PRISMA 2020 guidelines, a systematic search was conducted in Web of Science, PubMed, and SPORTDiscus up to April 2025. Eligible studies involved healthy athletes (aged 12-30 years) who completed ≥4-week lower-limb training interventions that either applied a greater stimulus to the weaker limb (e.g., starting sets with the weaker side or adding volume) or used unilateral training approaches that applied the same training stimulus to both limbs regardless of baseline ILA values. To be included, studies were required to assess both pre-to-post changes in ILA and at least one physical performance outcome. The risk of bias was assessed using a modified Cochrane tool.

Eleven studies comprising 297 athletes met the inclusion criteria. Reductions in ILA were more consistent in asymmetry-focused and unilateral training groups compared to general and bilateral training groups, respectively. Most interventions also led to improvements in physical performance, with asymmetry-focused and unilateral protocols typically producing greater gains in single-limb tasks, although bilateral training showed more favourable effects in bilateral tasks. However, variability in training protocols and outcome measures across studies limits the generalizability of these findings.

Asymmetry-focused strategies, such as starting unilateral exercises with the weaker limb or increasing its training volume, appear to be more effective for reducing ILA than non-individualized unilateral training. These approaches are practical, safe, and potentially beneficial in athletic settings. However, further high-quality research is needed to confirm their superiority over non asymmetry-focused unilateral or bilateral training and to establish clear guidelines for their implementation. Registration PROSPERO-CRD420251023232.