The purpose of this study was to investigate the relationship among core and lower extremity muscle function, foot posture, body mass index (BMI), and postural stability using foot-posture measures with moderate to high intra-tester and inter-tester reliability, and a postural-stability measure that considers both centre of pressure (COP) position and velocity.
The authors recruited 110 participants with no lower extremity injuries 6 months prior to the study, and no history of lower extremity surgery.
Before postural-stability testing, a force plate was used to weigh the participants. Next, the authors assessed dominant-limb, single-limb stance position postural stability on a force plate sampling at 100 Hz during three 10-second trials of the eyes-closed condition.
The eyes-closed condition was selected to increase the challenge to the somatosensory system and musculoskeletal components of the postural-control system.
Anterior, posterior and lateral core muscular-endurance testing consisted of a single time-to-failure trial in each position as described by McGill et al.
Dominant-limb arch index (AI) and navicular index (NI) ratios during 10% and 90% weight-bearing conditions were quantified using a digital photographic measurement method.
The authors assessed maximal isometric hip strength (flexion, extension, abduction, adduction, lateral rotation, medial rotation) using a handheld dynamometer.
The findings of the study confirmed the hypothesis that a composite of anthropometric, strength, endurance, and foot-posture variables would predict anteroposterior and mediolateral postural stability.
Foot posture was a predictor variable accounting for 4.4% and 4.2% of anteroposterior and mediolateral postural stability variance, respectively.
The negative correlation coefficients suggest that increased arch height is associated with decreased mediolateral postural stability.
The cause of the relationship between high-arch posture and mediolateral postural instability may be an anterior and lateral shift in COP and decreased foot mobility often associated with high-arch postures.
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