Abstract
BACKGROUND: The intrinsic foot muscles (IFMs) are known to contribute significantly to postural control, particularly during tasks requiring single-limb stability. However, their acute role under fatigued conditions remains unclear. This study aimed to investigate the acute effects of IFMs fatigue on static balance parameters during single-leg stance in healthy young adults. METHODS: Sixty-six participants performed a standardized IFMs fatigue protocol consisting of six exercises. Static balance was assessed using a stabilometric platform during single-leg stance with eyes open (EO) and closed (EC), both before and immediately after the fatigue protocol. Static balance parameters and trunk movements were analyzed. Paired t-tests were conducted, and effect sizes were calculated using Cohen's d. RESULTS: Following the intrinsic foot muscle fatigue protocol, during EO single-leg stance, medio-lateral CoP displacement increased (p = 0.003, d = 0.37), while sway speed decreased in both medio-lateral (p = 0.01, d = 0.31) and antero-posterior directions (p = 0.03, d = 0.26), along with a reduction in sway perimeter (p = 0.004, d = 0.36). In EC stance, medio-lateral trunk sway (p = 0.009, d = 0.14) and total trunk sway (p = 0.011, d = 0.39) significantly increased, with no other parameters showing significant changes (p > 0.05). CONCLUSION: This study highlights IFMs fatigue was associated with decreased sway speed and ellipse area despite greater CoPx variability, suggesting a role in modulating fine adjustments. Under EC conditions, increased trunk sway appeared to reflect a compensatory postural adjustment. Overall, these findings indicate that IFMs act not only as structural supporters but also as active contributors to postural control. TRIAL REGISTRATION: Not applicable.