Elasticity measures of lower leg muscles attributed to foot arch classifications: A comparison to dynamic balance across groups with and without ligamentous injury

Purpose: The purpose of this study was to examine differences, correlations, and predictive relationships between the elasticity of lower leg muscles, categories of arch height and mobility, and dynamic single-leg standing balance among participant groups of healthy, chronic ankle instability (CAI), and anterior cruciate ligament repair (ACLr). Participants: One hundred fifty (109 healthy, 24 CAI, 17 ACLr) recreationally active adults participated in this cross-sectional study. Procedures: Elasticity of the tibialis anterior (TAm), tibialis posterior (TPm), peroneal longus (PLm), and peroneal brevis (PBm) was measured with shear wave elastography (SWE) in non-weight-bearing (NWB) and weight-bearing (WB). The Arch Height Index was used to categorize arch height (low, neutral, high) and mobility (mobile, neutral, rigid). Dynamic balance (DB) was measured with the Y-Balance Test. ANOVAs, with Bonferroni corrections, were utilized to examine differences between and within the variables. Pearson correlations were utilized to calculate the relationship among variables. Linear and multinomial logistic regressions were utilized to determine the predictive relationship between variables. Results: Differences: For healthy participants, the results of this study revealed elasticity of multiple muscles are significantly different between/within positions of NWB/WB. A high arch had greater muscle elasticity than a low arch in NWB/WB. A significant interaction revealed elasticity of the TPm in NWB was less in a mobile arch versus a rigid arch. When comparing participant groups, there was a significant main effect for muscle elasticity and group in NWB/WB. The TPm had the greatest elasticity regardless of group. The ACLr group had the least elasticity regardless of muscle. Relationships: No relationship was found between DB and muscle elasticity in NWB/WB for healthy, CAI, or ACLr groups. Predictions: Arch height/mobility categories significantly predicted elasticity of the PLm, PBm, and TPm in NWB/WB. No variables were found to differentiate CAI from the healthy group; however, DB, elasticity of the TAm, TPm, and PBm in NWB/WB individually differentiated ACLr from the healthy group. Conclusion: This is the first study to utilize SWE to establish muscle elasticity by arch height and arch mobility categories across groups—healthy, CAI, and ACLr. These findings may be used as a comparison for future studies.