Effects of a 4-Week Intrinsic Foot Muscle Exercise Program on Motor Function

Abstract

PURPOSE: The purpose of this single-blinded randomized control trial was to study the effects of a 4-week intrinsic foot muscle (IFM) exercise program on motor function, perceived difficulty, and IFM motor activation measured using ultrasound imaging (USI) during three IFM exercises. METHODS: 24 healthy, recreationally active young adults with no history of ankle or foot injury who have never performed IFM exercises participated (12 males, 12 females; mean age=21.5±4.8 years; BMI = 23.5±2.9 kg/m2). Following randomization, participants allocated to the intervention group received a progressive home IFM exercise program performed daily. Participants in the control group did not receive any intervention and were asked not to alter their physical activity during the trial. Clinician-assessed motor performance (4-point scale: 0=does not initiate movement, 3=performs exercise in standard pattern), patient perceived difficulty (5 point Likert scale: 1=very easy, 5=very difficult), and USI motor activation measures (active thickness/resting) of the abductor hallucis (AbdH), flexor digitorum brevis (FDB), quadratus plantae (QP), and flexor hallucis brevis (FHB) were assessed during a toe spread out, hallux extension, and lesser toe extension exercise. The Wilcoxon signed rank test was used to assess the pre to post intervention motor performance and perceived difficulty measures. Repeated measures ANOVAs were used to analyze the USI measures. RESULTS: The intervention group demonstrated significant improvement in motor performance in the toe spread out exercise (pre=1.9±0.5, post=2.6±0.5, p=.008) and less perceived difficulty in the toe spread out (pre=3.1±1.3, post=2.3±1.2, p=.01), isolated hallux extension (pre=3.2±1.5, post=2.0±1.2, p=.005), and lesser toe extension (pre=1.9±0.7, post=1.2±0.4, p=.03) exercises. Both groups demonstrated increased USI motor activation in the AbdH during the toe spread out exercise (intervention: pre=1.07±.06, post=1.11 ± .08; control: pre=1.08±.06, post=1.11±.06, p=.05). No other significant main effects or group by time interactions were observed. CONCLUSION: A 4-week IFM exercise intervention resulted in improved motor performance and decreased perceived difficulty when performing the exercises, but not changes in USI measures of IFM activation.