Effects of a 4-Week Intrinsic Foot Muscle Exercise Program on Motor Function: A Preliminary Randomized Control Trial

Intrinsic foot muscle (IFM) exercises are utilized clinically in the treatment of foot and ankle conditions. However, the effectiveness of training on IFM motor function is unknown. To study the effects of a 4-week IFM exercise program on motor function, perceived difficulty, and IFM motor activation measured using ultrasound imaging (USI) during 3 IFM exercises. Single-blinded randomized control trial. Laboratory. A total of 24 healthy, recreationally active young adults without history of ankle-foot injury who have never performed IFM exercises participated (12 males and 12 females; mean age = 21.5 [4.8] y; body mass index = 23.5 [2.9] kg/m²) Following randomization, participants allocated to the intervention group received a 4-week progressive home IFM exercise program performed daily. Participants in the control group did not receive any intervention. Clinician-assessed motor performance (4-point scale: 0 = does not initiate movement and 3 = performs exercise in standard pattern), participant-perceived difficulty (5-point Likert scale: 1 = very easy and 5 = very difficult), and USI motor activation measures $$ of the abductor hallucis, flexor digitorum brevis, quadratus plantae, and flexor hallucis brevis were assessed during toe-spread-out, hallux-extension, and lesser-toe-extension exercises. 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), 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 abductor hallucis during the toe-spread-out exercise (intervention: pre = 1.07 [0.06], post = 1.11 [0.08] and control: pre = 1.08 [0.06], post = 1.11 [0.06]; P = .05). No other significant main effects or group by time interactions were observed. 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 compared with a control group.