The effect of additional activation of the plantar intrinsic foot muscles on foot dynamics during gait

Abstract

Background: The plantar intrinsic foot muscles (PIFMs) contribute to support the medial longitudinal arch. But the functional role of the PIFMs during dynamic activities is not clear. The purpose of this study was to examine the change in the foot dynamics during gait accompanied with the change in the PIFMs activity to determine the functional role of the PIFMs during gait.

Methods: Twenty healthy male subjects were randomly assigned to the electrical stimulation group (ESG) or control group (CG). In the ESG, the electrical stimulation to the PIFMs was provided from mid-stance to pre-swing using surface electrodes to simulate reinforcement of the PIFMs. The foot dynamics during the stance phase of gait was measured using a 3D motion analysis, and the amount of change from baseline (electrical stimulation was not provided) was compared between groups using an independent sample t-test.

Results: In the ESG, the timing for the navicular height to reach the minimum value was significantly later, and the vertical ground reaction force (2nd peak) significantly decreased more. There were no group differences in the amount of change from baseline on gait velocity, stance phase duration, minimum navicular height and ground reaction force in other directions.

Conclusion: Results from this study showed that the functions of the PIFMs most likely include shock absorption and facilitation of efficient foot ground force transmission during the stance phase of gait.

Keywords: 3D motion analysis; Electrical stimulation; Gait; Plantar fasciitis; Plantar intrinsic foot muscle.