Elsevier

Gait & Posture

Volume 45, March 2016, Pages 35-40
Gait & Posture

Ankle muscle coactivation during gait is decreased immediately after anterior weight shift practice in adults after stroke

https://doi.org/10.1016/j.gaitpost.2016.01.006Get rights and content

Highlights

  • We studied effects of balance practice on ankle muscle coactivation after stroke.

  • Gait speed immediately increased after anterior weight shift practice.

  • Ankle muscle coactivation on the paretic side decreased after balance practice.

  • There were no significant relationships between changes in these outcomes.

  • Improvement in gait speed coincided with decreased muscle coactivation.

Abstract

Increased ankle muscle coactivation during gait has frequently been observed as an adaptation strategy to compensate for postural instability in adults after stroke. However, it remains unclear whether the muscle coactivation pattern increases or decreases after balance training. The aim of this study was to investigate the immediate effects of balance practice on ankle muscle coactivation during gait in adults after stroke. Standing balance practice performed to shift as much weight anteriorly as possible in 24 participants after stroke. The forward movement distance of the center of pressure (COP) during anterior weight shifting, gait speed, and ankle muscle activities during 10-m walking tests were measured immediately before and after balance practice. Forward movement of the COP during anterior weight shifting and gait speed significantly increased after balance practice. On the paretic side, tibialis anterior muscle activity significantly decreased during the single support and second double support phases, and the coactivation index at the ankle joint during the first double support and single support phases significantly decreased after balance practice. However, there were no significant relationships between the changes in gait speed, forward movement of the COP during anterior weight shifting, and ankle muscle coactivation during the stance phase. These results suggested that ankle muscle coactivation on the paretic side during the stance phase was decreased immediately after short-term anterior weight shift practice, which was not associated with improved gait speed or forward movement of the COP during anterior weight shifting in adults after stroke.

Introduction

Gait is a fundamental component of activities of daily living, and regaining the ability to walk is a major goal of stroke rehabilitation for adults with hemiplegia [1]. Common characteristics of hemiplegic gait are decreased gait speed [2], asymmetrical gait pattern [2], and increased energetic cost [3]. These gait dysfunctions are mainly caused by impaired function of the paretic lower limb due to muscle weakness [4], sensory dysfunction [4], and disturbed control of lower limb muscle activation [5], [6]. One of the well-documented muscle activation patterns during gait after stroke is a coactivation pattern of several lower limb muscles [5], [6].

Postural control ability is strongly related to gait speed, and balance training is found to improve postural control ability and gait speed in adults after stroke [7]. It is well documented that improvements in postural control following balance training are accompanied by adaptations within the central nervous system [8]. These adaptations of neuromuscular properties are represented as changes in lower limb muscle activation during postural tasks [8], [9], [10]. Balance training has been shown to lead to decreased antagonist muscle coactivation in healthy young adults [9]. In healthy older adults, an enhancement in balance performance was concurrently observed with decreased muscle coactivation after balance training [10]. These previous results suggest that decreased muscle coactivation is helpful for improving balance performance in healthy subjects.

Increased ankle muscle coactivation on both the paretic and non-paretic sides during gait is frequently observed in adults after stroke [3], [11], [12], [13], and it has both positive and negative effects on functional performance. Lower limb muscle coactivation is an important postural control mechanism that contributes to enhancement of postural stability during the weight acceptance phase in healthy subjects [14], and difficulty of postural control has been shown to lead to increased ankle muscle coactivation during beam walking in healthy subjects [15]. Therefore, increased ankle muscle coactivation during gait represents an adaptation strategy to compensate for postural instability in adults after stroke [11], [13], and it may be possible to improve gait function using this compensation strategy by increasing ankle muscle coactivation after balance training in adults after stroke. However, excessive muscle coactivation induces high joint stiffness, which reduces the degrees of freedom for postural control [16], and induces a high energetic cost during gait in adults after stroke [3]. Therefore, a decrease in ankle muscle coactivation after balance training may indicate efficient improvement in gait speed in adults after stroke. However, no previous studies have investigated the changes in ankle muscle coactivation during gait after balance training in adults after stroke. It is important to investigate whether the muscle coactivation pattern increases or decreases after balance training for clarifying the mechanisms by which balance training may improve gait speed in adults after stroke.

The aim of the present study was to investigate the immediate effects of short-term balance practice on gait speed and ankle muscle coactivation during gait in adults after stroke. We hypothesized that ankle muscle coactivation during gait would decrease, associated with improvements in gait speed after balance practice.

Section snippets

Subjects

Twenty-four community-dwelling subjects with chronic hemiplegia after stroke (age 57.8 ± 9.9 years, height 164.3 ± 9.5 cm, weight 62.2 ± 9.8 kg, 15 men, time post-stroke 4.7 ± 4.3 years, 14 right side affected) and age- and sex-matched nine healthy control subjects (55.8 ± 3.9 years, 165.0 ± 8.5 cm, 60.4 ± 10.5 kg, 6 men) participated in the present study. Inclusion criteria of the participants after stroke were (1) a single stroke >6 months prior to this study, (2) no history of neurological diseases (e.g.,

Comparison of ankle muscle coactivation between participants after stroke and healthy controls

Gait speed before balance practice was 0.66 ± 0.30 m/s in participants after stroke and 0.58 ± 0.06 m/s in healthy controls. There was no significant difference in gait speed between participants after stroke and healthy controls (unpaired t-test; p = 0.270). The CoI during the DS1, SS, and DS2 phases on both the paretic and non-paretic sides were significantly higher than in healthy controls (DS1 p = 0.012 and p = 0.032, SS p = 0.016 and p = 0.003, DS2 p < 0.001 and p = 0.018, healthy controls vs. paretic and

Discussion

The present study shows that ankle muscle coactivation during the stance phase is decreased immediately after anterior weight shift practice in adults after stroke. After balance practice, forward movement of the COP during anterior weight shifting and gait speed immediately increased when compared to those before balance practice. Furthermore, ankle muscle coactivation during some support phases on the paretic side concurrently decreased after balance practice. However, in contrast to our

Conclusions

Anterior weight shift practice improved postural control ability during this task in adults after stroke and the postural improvement might transfer to gait. Gait speed improved immediately after anterior weight shift practice along with decreased ankle muscle coactivation during the first double support and single support phases on the paretic side in adults after stroke. Therefore, short-term balance practice could improve gait speed, which coincides with decreased ankle muscle coactivation

Conflicts of interest statement

There are no conflicts of interest related to the preparation of this manuscript or the research discussed in the present study.

Acknowledgments

This work was partially supported by Grant-in-Aid for Japan Society for the Promotion of Science fellows (25-2431). We wish to thank the staff of Kawamuragishi Co., Ltd., Osaka, Japan, for recruiting the participants and providing the location for measurements.

References (29)

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