Control of gait is usually altered following stroke, and it may be further compromised by overexertion and fatigue. This study aims to quantitatively assess patients' gait stability during six-minute walking, measuring upper body accelerations of twenty patients with stroke (
The recovery of walking ability is one of the most relevant functional targets after a cerebrovascular event, but this goal is generally obtained by only 50–60% of patients [
Prolonged walking in living environment is even more challenging than short distances walked in hospital settings. Furthermore, overexertion can be detrimental for physical and mental conditions of people with stroke: for these patients, fatigue prevalence has been estimated to be up to 70% [
Gait dynamic stability could be defined as the capacity to move the body segments in a coordinated fashion so that the body could be displaced with a proper speed (i.e., functional to the required task, such as crossing the road safely) minimizing upper body oscillations [
The aim of this study is to quantify the potential effects of fatigue, induced by effortful walking, on gait dynamic stability of patients with stroke. The hypothesis that we wanted to test was if gait stability is reduced during prolonged walking in people with subacute stroke. To achieve this goal, we have measured upper body accelerations during the six-minute walking test performed by ambulatory inpatients.
Twenty patients with stroke and ten age-matched healthy subjects were enrolled in this study (see Table
Demographic and clinical characteristics of participants. Mean ± standard deviation (95% confidence interval) or median (first and third quartiles) of demographic characteristics, clinical features and scale scores at the moment of the 6MWT. The fourth and the last columns report the
Characteristics | CG | PG | PG1 | PG2 | ||
( | ( | CG versus PG | ( | ( | PG1 versus PG2 | |
Age (years old) | 62.8 ± 9.7 ( | 64.4 ± 13.0 ( | 0.734 | 62.7 ± 14.7 ( | 67.0 ± 10.0 ( | 0.468 |
Height (m) | 1.68 ± 0.10 ( | 1.69 ± 0.11 ( | 0.795 | 1.69 ± 0.13 ( | 1.69 ± 0.09 ( | 0.975 |
Body mass Index (kg/m2) | 25.5 ± 2.4 ( | 26.29 ± 4.17 ( | 0.594 | 26.86 ± 4.33 ( | 25.43 ± 4.04 ( | 0.469 |
Women | 5 | 6 | 0.284 | 4 | 2 | 0.690 |
Men | 5 | 14 | 8 | 6 | ||
Time from the event (days) | — | 132 ± 103 ( | — | 101 ± 36 ( | 180 ± 149 ( | 0.091 |
Length of stay (days) | — | 92 ± 41 ( | — | 83 ± 32 ( | 104 ± 51 ( | 0.277 |
Barthel index | — | 60 | — | 70 | 46 | 0.341 |
( | ( | ( | ||||
Functional Ambulation Classification | — | 4 | — | 4 | 3 | 0.327 |
( | ( | ( | ||||
Right | — | 12 | — | 7 | 5 | 0.852 |
Left hemiparesis | 8 | 5 | 3 | |||
Ischemic | — | 18 | — | 11 | 7 | 0.761 |
haemorrhagic | 2 | 1 | 1 |
To assess the independency in activities of daily living and the walking ability of our patients, we administered them the Barthel Index (BI) and the Functional Ambulation Classification (FAC), respectively. BI is one of the best known and commonly used scales to assess the degree of independence a patient demonstrates in various activities of daily living, including mobility and transfers (in particular, bowel and bladder function, grooming, toilet use, feeding, transfers, mobility, dressing, climbing stairs, and bathing). Its total score ranges from 0 (total dependence) to 100 (total independence) [
The six-minute walking test (6MWT) was used to measure walking endurance, as usually done in clinical settings [
During the 6MWT, the participants wore an elastic belt including a light wearable inertial sensor device (FreeSense, Sensorize s.r.l., Rome; sampling frequency = 100 Hz, weight = 93 g) located on their back in correspondence of L2-L3 spinous processes, close to their body centre of mass. This device contains a triaxial accelerometer to separately measure three accelerations, each one along one of the three body axes (anteroposterior AP, laterolateral LL, and craniocaudal CC).
Accelerometer signals were 20 Hz low-pass filtered, transformed to give a mean equal to zero, and summarized in their root mean square (RMS) [
For each one of the six minutes of walking, the mean walking speed was computed as the meters walked in that minute divided into 60 s, and the mean RMS was computed on the accelerometric signals recorded in a central part of the linear walking performed in that minute (see Figure
The acceleration signal along laterolateral direction of a patient. The grey large bands highlight the analysed part of the signal for each one of the 6 minutes of the test. The thin red lines indicate the end of each 20 m lap.
Mean ± standard deviation and 95% confidence interval (CI95%) have been computed for continuous measures and median and 1st and 3rd quartiles for scale scores. Analogously,
An analysis of variance (ANOVA) was performed in order to compare the values of walked distance and walking speeds among the three groups (between subjects factor), followed by post hoc comparison performed with Tukey’s test (see Table
Gait parameters. Mean ± standard deviation (CI95%) of gait parameters recorded during 6MWT for the three groups of participants. The last two columns reported the statistical analyses. For PG2, the last minute walking speed was the minute before stopping.
Gait parameters | PG1 | PG2 | CG | Analysis | |
ANOVA | Post-hoc | ||||
PG1, PG2, CG | PG1 versus PG2 | ||||
Walked distance (m) | 226 ± 111 | 94 ± 73 | 413 ± 57 | ||
( | ( | ( | |||
Walking speed (m/s) | 0.63 ± 0.31 | 0.37 ± 0.25 | 1.15 ± 0.16 | ||
( | ( | ( | |||
1st minute | 0.62 ± 0.30 | 0.43 ± 0.30 | 1.17 ± 0.18 | ||
Walking speed (m/s) | ( | ( | ( | ||
last minute | 0.64 ± 0.32 | 0.32 ± 0.18 | 1.16 ± 0.13 | ||
Walking speed (m/s) | ( | ( | ( |
A repeated measure ANOVA was performed on the RMS values of participants able to complete the test (PG1 and CG) to assess the changes over time (within-factor: 1, 2, 3, 4, 5, and 6 minutes) and the effects of group (between-factor: PG1, CG) and body axis (between-factor: AP, LL, and CC). Conversely, for PG2, in which not all subjects walked for the same time, paired
Twelve of the twenty patients were able to complete the 6MWT (subgroup PG1) and eight patients asked to definitively stop the test before its planned conclusion (PG2). The clinical characteristics of PG1 and PG2 are summarized in Table
In terms of gait performance, a significant difference was observed in terms of walked distance among the three groups (Table
Despite the reduction of walking speed observed in PG2, their acceleration RMSs were not reduced between the first and the last minutes of the test (
Acceleration RMS for PG1 ((a), (c), and (e)) and CG ((b), (d), and (f)) along anteroposterior ((a) and (b)), laterolateral ((c) and (d)) and craniocaudal ((e) and(f)) directions. Regression lines and relevant coefficient of determination
In this study, we observed a progressive reduction of gait dynamic stability in patients with stroke during prolonged walking. To test the relationship between walking endurance and gait stability, we compared the performances of inpatients with those of an age- and height-matched group of healthy subjects, combining the 6-minute walking test with the measure of upper body accelerations.
As expected, the walked distance at the end of the test and the mean walking speed were both lower in patients than in healthy subjects. The lower walking speed of patients implied lower accelerations, facilitating their control of upper body stability [
During the six minutes of the test, neither walking speed nor trunk accelerations significantly varied for control subjects. Conversely, patients showed a progressive reduction of their walking speed and/or gait stability.
In healthy subjects, it was already found that a reduced gait velocity results in a corresponding reduction of acceleration amplitudes [
Our results suggest that patients used two possible alternative strategies to perform the 6MWT. Some of them were able to keep their speed quite constant during walking, despite a slight but progressive reduction of their upper body stability. These subjects were mainly those of PG1, that is, the group able to complete the test. Other subjects seemed to apply a compensation strategy based on the reduction of their walking speed. It probably facilitated the management of their progressive reduction of gait stability during this effortful walking task. As stated above, the reduction of walking speed is, in fact, a suitable strategy for reducing upper body accelerations [
In previous studies, for patients with chronic stroke performing the 6MWT, neither differences in velocities for each 1-minute interval [
However, far too little attention has been paid to the reduction of gait stability during prolonged walking, which may potentially increase the risk of falls [
In fact, in this study, we found an increment of patients’ upper body accelerations, especially along anteroposterior and laterolateral directions over six-minute walking. These accelerations have already been showed as the most informative for assessing the gait stability and also the most correlated with the risk of fall [
The main limitation of our study is the reduced size of healthy and patient samples especially in respect of the many features of stroke. Wider samples are needed in future studies to further explore the differences between patients who could and those who could not complete the 6-minute walking test. Another important aspect that needs to be further investigated is the stabilizing effect of the use of a cane or of the therapist’s touch during walking. It should be noted that in our study the needs of external helps were similar in the two subgroups of patients (as shown by similar autonomy walking level: see values of FAC scores in Table
Our results should be read in conjunction with those of Lerdal and colleagues in which it has been shown how an increased mobility may increase exposure to fall opportunities [
Patients with stroke showed a reduction of walking speed and/or a reduction of gait stability during prolonged walking. In particular, the patients able to complete the six-minute walking test maintained a steady speed over the course of the walk, but their upper body accelerations progressively increased, exposing them to the risk of falling.