Muscle-activation onset times with shoes and foot orthoses in participants with chronic ankle instability

Abstract

Context: Participants with chronic ankle instability (CAI) use an altered neuromuscular strategy to shift weight from doublelegged to single-legged stance. Shoes and foot orthoses may influence these muscle-activation patterns. Objective: To evaluate the influence of shoes and foot orthoses on onset times of lower extremity muscle activity in participants with CAI during the transition from double-legged to single-legged stance. Design: Cross-sectional study. Setting: Musculoskeletal laboratory. Patients or Other Participants: A total of 15 people (9 men, 6 women; age = 21.8 ± 3.0 years, height = 177.7 ± 9.6 cm, mass = 72.0 ± 14.6 kg) who had CAI and wore foot orthoses were recruited. Intervention(s): A transition task from double-legged to single-legged stance was performed with eyes open and with eyes closed. Both limbs were tested in 4 experimental conditions: (1) barefoot (BF), (2) shoes only, (3) shoes with standard foot orthoses, and (4) shoes with custom foot orthoses (SCFO). Main Outcome Measure(s): The onset of activity of 9 lower extremity muscles was recorded using surface electromyography and a single force plate. Results: Based on a full-factorial (condition, region, limb, vision) linear model for repeated measures, we found a condition effect (F3,91.8 = 9.39, P