Change in Coefficient of Fatigability Following Rapid, Repetitive Movement Training in Post-Stroke Spastic Paresis: A Prospective Open-Label Observational Study

Background

In post-stroke patients, the possibility of performing an active ankle dorsiflexion movement is favorable for the recovery of gait. Moreover, the fatigue due to repetitive active ankle dorsiflexion could reduce the speed gait. We assessed the change in coefficient of fatigability of active ankle dorsiflexion after a home-based self-rehabilitative procedure in post-stroke patients.

Methods

In a prospective open-label observational study conducted in 2 university hospitals, a home-based self-rehabilitation treatment comprising two 12-minute sessions per day (3 times per week for 3 months) was performed by 10 outpatients with post-stroke lower limb impairment. Each session consisted of three 1-minute series of repeated active ankle dorsiflexion efforts at maximal speed on the paretic side, each one followed by 3-minute bouts of triceps surae stretch. Coefficients of fatigability of dorsiflexion and 10-meter barefoot ambulation speed were evaluated at baseline and at the end of the program.

Results

At 3 months of follow-up, there was a decrease in the coefficients of fatigability of ankle dorsiflexion, both with knee flexed and extended (respectively from 8% to 2% and from 6% to 2%; P < .01), associated with an increase in comfortable ambulation speed (from .24 to .26 m/s; P < .05).

Conclusions

The reduction of coefficient of fatigability of ankle dorsiflexion, together with walking speed improvement, suggested the effectiveness of self-rehabilitation using alternated periods of self-stretch and rapid alternating efforts in the paretic lower limb after stroke.

Introduction

Motor impairment is common in patients with stroke and causes dependency in activities of daily living.¹ A number of physiological disorders may cause difficulty in generating appropriate limb movements, such as antagonist muscle overactivity (spastic co-contraction, spastic dystonia), antagonist stiffness, and agonist paresis.2, 3, 4 These disorders cause abnormal force coupling between agonists and antagonists, and abnormal muscle activation patterns particularly in gait.2, 3, 4, 5 When walking, plantar flexor co-contraction during swing phase combined with reduced force production from ankle dorsiflexors impede the gait cycle and may lead to instability.5, 6, 7 In stance phase, plantar flexor overactivity may be responsible for the development of equinovarus foot deformity, which reduces the base of support with negative consequences for both balance and gait.⁷

Therefore, it is important for clinicians to reliably assess motor impairment in spastic paresis after stroke, to identify appropriate rehabilitative and potential pharmacological treatments.8, 9, 10, 11, 12, 13 In particular, the assessment of limb impairment should include muscle extensibility assessment in passive movements and consider both antagonist overactivity and agonist paresis in active movements.⁸ To assess resistance to passive movements, Tardieu et al's⁹ and Ashworth's¹⁰ scales are commonly used measures of spasticity and tone, respectively, in the clinical practice, even though the Tardieu Scale differentiates spasticity from contracture, unlike the Ashworth Scale scoring.¹¹

A particular parameter included in the evaluation of motor impairment, especially for the agonist and antagonist muscles around the ankle, is the measure of the amplitude of active ankle dorsiflexion movement on the paretic side. The objective is to assess the capacity of agonist activation to overcome passive and active resistance of the tested muscle group (ankle plantar flexors), and for this aim we asked the patient to accomplish 1 movement of maximal amplitude against the tested muscles.⁸ In the Five-Step Assessment, the amplitude obtained in that active, maximal single movement is called X_A.8, 12 This amplitude reached at the end of the maximal active movement represents balance between the forces generated by agonist activation and those related to passive (stiffness by increased viscoelasticity) and active (spastic co-contraction) resistances opposed by the tested muscle group.¹²

In individuals with post-stroke hemiparesis, it is postulated that active movement amplitudes can be gradually increased using a rehabilitation technique involving daily series of repeated efforts of active movement reaching the maximal possible amplitude against the antagonist in a given time, 15 seconds, for example.¹⁴ In such series of efforts, the decrement from the angle obtained at the first effort to the final angle still achieved at the last effort after 15 seconds of repeated efforts (termed X_A15) may represent fatigability of performance, essentially of central origin.12, 15 The ratio (X_A-X_A15)/X_A has thus been defined as the coefficient of fatigability.¹⁴ The primary aim of this study was to evaluate whether the coefficient of fatigability of ankle dorsiflexion might change after a specific home-based, self-rehabilitative procedure in stroke patients.¹⁴ The secondary aim was to assess whether gait improvement might parallel changes in coefficient of fatigability of ankle dorsiflexion.