Association between the Strength of Flexor Hallucis Brevis and Abductor Hallucis and Foot Mobility in Recreational Runners

Different measurements of foot morphological characteristics can effectively predict foot muscle strength. However, it is still uncertain if structural and postural alterations leading to foot pronation could be compensated with more efficient function of the intrinsic foot muscles and how mobility and strength are associated. Additionally, the relationship between foot mobility and the strength of the intrinsic muscles that control the foot arch is still unclear. Therefore, this study aimed to investigate the morphological parameters between dominant and non-dominant feet and the relationship between the intrinsic foot muscle strength and foot mobility in recreational runners. We used a cross-sectional study design to evaluate twenty-four healthy recreational runners (minimum 15 km/week) with an average training history of 70 ± 60 months. Foot Posture Index (FPI-6), isometric intrinsic muscle strength, overall morphology, and normalized mobility of both feet were assessed. Parametric tests analyzed the unidimensional measures, and paired analysis determined differences between dominant and non-dominant sides. Pearson’s and Spearman’s correlation coefficients determined the relationships between normalized strength and the variables of interest (CI = 95%). There was no significant association between intrinsic foot muscle strength and mobility. The only difference observed was between the dominant and non-dominant foot regarding the normalized foot length and midfoot width during non-weight-bearing, with small and medium effect sizes, respectively. Neither foot morphology nor foot mobility was associated with strength from intrinsic foot muscles in healthy recreational runners. Further work should explore the relationship investigated in our study with professional athletes and runners with symptomatic lower limb injuries to potentialize training and rehabilitation protocols.