The influence of different heel heights on squatting stability: a systematic review and network meta-analysis

The back squat (BS) is one of the most effective exercises for enhancing lower limb strength, but an unstable squat can increase shear forces in the lower back. Understanding how to assess the squat stability is useful for avoiding potential sports injury. During the BS, the trunk lean and center of pressure (COP) are relevant to squat safety, and these kinematics can be altered by elevating the heel. However, there is no relevant meta-analysis on the impact of different heel heights on squat stability. This study aims to bridge the gap in the literature by conducting a systematic review and network meta-analysis on how heel elevation affects squat stability. By quantifying the influence of different heel heights on key biomechanical parameters, such as the center of pressure deviation and ankle dorsiflexion, the study provides actionable insights for athletes, trainers, and clinicians. Fourteen articles were included, and the majority of these studies demonstrated that elevated heels (EHs) can reduce COP deviation and trunk lean. In addition, 25 mm heels may be the preferred option for squat stability in the AP direction when COP data and network meta-analysis are combined. However, in the ML direction, the capacity to maintain balance is rather questionable; when ankle peak dorsiflexion is combined, 8 mm heels have higher COP deviation values and 5 mm heels have lower COP deviation values. Regarding limitations, reliance on a single bias assessment tool (Cochrane Risk of Bias Tool) might not fully capture methodological variability across non-RCT studies. Future systematic reviews could consider using multiple bias assessment tools for robust assessment.