Evaluating the Function of the Foot Core System in the Elderly

Summary

The functional core stability of the foot contributes to the human static posture and dynamic activities. This paper proposes a comprehensive evaluation for the function of the foot core system, which combines three subsystems. It may provide increased awareness and multifaceted protocol to explore the foot function among different populations.

Abstract

As a complex structure to link the body and the ground, the foot contributes to postural control in human static and dynamic activities. The foot core is rooted in the functional interdependence of the passive, active, and neural subsystems, which combine into the foot core system controlling foot motion and stability. The foot arch (passive subsystem), responsible for load, is considered the functional core of the foot, and its stability is necessary for normal foot functions. The functional abnormalities of the foot have been widely reported in the elderly, such as weakness of toe flexor muscles, abnormal foot postures, and decreased plantar sensory sensitivity. In this paper, a comprehensive approach is introduced for evaluating the foot function based on foot core subsystems. The strength and morphology of the foot intrinsic and extrinsic muscles were used to evaluate the foot muscle (active subsystem) function. The doming strength test was applied to determine the function of foot intrinsic muscles, while the toe flexion strength test focused more on the function of extrinsic muscles. The navicular drop test and foot posture index were applied to evaluate foot arch (passive subsystem) function. For the neural subsystem, the plantar light touch threshold test and two-point discrimination test were used to assess plantar tactile sensitivity at nine regions of the foot. This study provides new insights into the foot core function in the elderly and other populations.

Introduction

The human foot is a highly complex structure, consisting of bones, muscles, and tendons that attach to the foot. As a segment of the lower extremity, the foot constantly provides direct source contact with the supporting surface and hence contributes to weight-bearing tasks¹. Based on the complex biomechanical interplay between muscles and passive structures, the foot contributes to shock absorption, adjusts for irregular surfaces, and generates momentum. Evidence shows that the foot contributes meaningfully to postural stability, walking, and running^2,3,4

Protocol

This study was conducted at the Sports Medicine and Rehabilitation Centre, Shanghai University of Sport, and has been approved by the ethics committee of the Shanghai University of Sport (No. 102772020RT001). Before the test, the participants were given details about the experimental purpose and procedures; all participants signed the informed consent.

1. Participant selection

1. Include participants who (1) are aged over 60 years old; (2) can maintain standing position alone; (3) can walk independently, without help from others, prosthesis, or mobility aids; (4) can display normal cognitive function and can unders....

Results

In this study, 84 participants were included for measurement. The young group included 42 university students with an average age of 22.4 ± 2.9 years and height of 1.60 ± 0.05 m. The elderly group included 42 community-dwelling elderly with an average age of 68.9 ± 3.3 years and height of 1.59 ± 0.05 m.

Representative active subsystem results
The morphology and strength of foot muscles are used to determine the function of the active subsystem. Muscle strength data is norm.......

Discussion

The presented protocol is used to measure the characteristics of the foot in the elderly, which provides a comprehensive assessment to investigate foot core stability, including the passive, active, and neural subsystems. This new paradigm illuminates the foot function that interacts to stabilize the foot and sustain sensorimotor function in daily activities³³. In previous studies, the researchers paid more attention to exploring foot deformity; toe flexion strength; diminished plantar sensory; an.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Diagnostic Ultrasound System	Mindray		It is used in clinical ultrasonic diagnostic examination.
ergoFet dynamometer	ergoFet		It is an accurate, portable, push/pull force gauge, which is designed to be a stand-alone gauge for capturing individual force measurements under any job condition.
Height vernier caliper			It is an accurate measure tool for height.
LabVIEW			It is a customed program software for strength analysis.
Semmes-Weinstein monofilaments	Baseline		It consists of 20 pieces, and each SWM haves an index number ranging from 1.65 to 6.65, that is related with a calibrated breaking force.
Two-Point Discriminator	Touch Test		It is a set of two aluminum discs, each containing a series of prongs spaced between 1 to 15 mm apart.