The role of enhanced plantar-surface sensory feedback on lower limb EMG during planned gait termination

Abstract

Purpose/aim of the study: Generation of smooth movement relies on the central nervous system (CNS) having information from the visual, vestibular and somatosensory systems to effectively execute motor behaviour. Recently, cutaneous afferent inputs have been linked to lower leg motorneuron pools, resulting in a growing interest of adding texture to the plantar foot sole interface as a novel method to facilitate cutaneous feedback. The aim of this study was to characterize the changes in magnitude and temporal organization of muscle activity, and to investigate motor output changes from enhanced tactile feedback during perturbed gait termination.

Materials and methods: Thirty young adults experienced an unpredictable platform perturbation when completing planned gait termination. The study manipulated two experimental variables: 1) direction of platform tilt (anterior, posterior, medial, lateral), and 2) foot sensory facilitation (non-facilitated, facilitated). Upper and lower leg EMG onset, cessation time and integrated EMG (iEMG) were measured in addition to common gait parameters (walking velocity, step length, step width).

Results: Gait termination over a textured surface resulted in significantly earlier upper leg EMG onset times and modified iEMG of rectus femoris, vastus medialis and biceps femoris muscles.

Conclusions: Results of this study suggest that the addition of cutaneous feedback under the plantar-surface of the foot increases the ability to generate an earlier muscle response, consequently improving response ability to an unexpected perturbation. Secondly, enhanced tactile feedback appears to inform the CNS of the magnitude of the threat to the balance control system, providing additional insight into how the CNS uses enhanced tactile feedback during a gait termination task.

Keywords:

• Cutaneous sensation
• gait termination
• texture
• foot
• cutaneous mechanoreceptors

Acknowledgements

The authors would like to thank Justin Tsung who participated in pilot testing and initial data collection of this study, and Monica Meserve for the Figure 1 design.

Disclosure statement

Stephen Perry holds a patent for a balance-enhancing insole (Maki, Perry, McIlroy, US 6,237,256 B1, 2001) and is the CEO of Balancepro, Inc. that is involved in the commercialization of the ‘Balancepro’ insole. Kelly Robb is a Canadian Certified Pedorthist, has submitted a patent for a textured insole (CAN, US Patent Offices, 2020), and has intention of using textured foot orthotics in future clinical practice.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

Funding from the Natural Science and Engineering Research Council of Canada [NSERC-RGPIN-2020-06603] and the Canadian Foundation for Innovation (CFI) supported this study.