EFFECT OF SHORT FOOT EXERCISES ON LOWER-LIMB MOTOR CONTROL DURING SINGLE-LEG STANDING IN PEOPLE WITH FLATFOOT

M. Suzuki¹, H. Kuruma², K. Kato¹, Y. Gota¹, H. Kase¹, H. Fujimoto¹, R. Nagashima¹

¹Seikeikai-Chiba Medical Center, Rehabilitation, Chiba, Japan, ²Tokyo Metropolitan University, Physical Therapy, Tokyo, Japan

Background: Intrinsic foot muscles play an important role in lower-limb motor control, including biomechanical and neuromuscular control. The common exercises for intrinsic foot muscles are the short foot (SFE) and toe curl (TC) exercises. In our pilot study, SFE have significantly greater abductor hallucis activity than TC did. However, the effect of SFE on lower-limb motor control has not yet been reported.

Purpose: To evaluate the effects of SFE on lower-limb motor control during single-leg standing (SLS) in people with flatfoot.

Methods: This was a randomized controlled trial, which included 36 participants with a foot posture index-6 of ≥ 7. The participants were randomly assigned to the SFE or TC group and assessed pre- and post-intervention. We assessed the navicular drop test, toe grip strength, plantar sensation, and SLS. The navicular drop test was performed using the Digital Caliper. Toe grip strength was measured using the Toe grip dynamometer. Plantar sensation was assessed using a Semmes-Weinstein monofilament. SLS was assessed by asking the participants to raise, hold, and lower the leg for 3 s each. The mean center-of-pressure amplitude in the anteroposterior and mediolateral directions was measured using a force plate. The onset of gluteus maximus and medius contractions was measured using a wireless surface electromyography. The angles of forefoot/hindfoot pronation, hip adduction, and lateral pelvic shift were measured using a 3D-motion analysis system. The exercises were performed with a hold-and-rest sequence of 5 s each for 5 min. In the first four weeks, the participants performed the exercises while sitting. In the next two weeks, they performed the exercises while standing. Finally, SLS was performed during the last two weeks. Physical therapists provided online instructions once a week. Face-to-face instructions were provided if deemed necessary. Independent t-test or Mann-Whitney U test was used to analyze characteristic data. Mixed-model repeated-measures analysis of variance was used for data assessment, with group, time, and interaction as dependent variables. Paired t-tests and Bonferroni corrections were conducted for significant main effects or interactions.

Results: There were no significant differences in the characteristic data between groups. The SFE group showed significantly increased toe grip strength (p<0.001, 95% confidence interval; CI: 2.2-4.4, d: 1.5), decreased mean center-of-pressure amplitude in the mediolateral direction (p=0.028, 95% CI: 0.1-1.0, d: 0.6), and accelerated onset of gluteus maximus (p=0.01, 95% CI: 105.3-511.1, d: 0.8) and medius (p<0.001, 95% CI: 229.4-569.1, d: 1.2) contractions post-intervention. The TC group showed no significant differences in any of the assessed parameters.

Conclusions: SFE contributed to a lower neuromuscular control in individuals with flatfoot.

Implications: Intrinsic foot muscle exercises improve neuromuscular control in the lower limbs. Further research is needed to externally validate these effects on motor control.

Funding acknowledgements: This research was not funded.

Keywords:
Short foot exercise
Intrinsic foot muscles
Neuromuscular control

Topics:
Musculoskeletal: lower limb
Musculoskeletal
Orthopaedics

Did this work require ethics approval? Yes

Institution: Tokyo Metropolitan University

Committee: Tokyo Metropolitan University, Arakawa Campus Research Ethics Committee

Ethics number: 21039