Anouk Lamontagne

Faster Is Better. Implications for Speed-Intensive Gait Training After Stroke

Background and Purpose— The instantaneous adaptations to speed and load changes during overground locomotion have major implications for mobility after stroke. We examined the extent to which stroke subjects could increase their overground walking speed with respect to speed and unloading changes. Methods— Twelve subjects with a unilateral stroke were evaluated while walking overground full weight bearing (FWB) or with body weight support (BWS) at preferred or fast speed. On the basis of their preferred walking speed, subjects were classified as high (≥45 cm/s) or low functioning (<45 cm/s). Gait speed, temporal distance factors (TDFs), as well as movements and muscle activation of the lower limbs were measured and compared across the conditions. Results— FWB-Fast condition induced marked (165%) increment in gait speed in all subjects. BWS at preferred speed induced faster speeds in low- but not the high-functioning subjects, whereas combined BWS and fast walking yielded further speed increments in the high-functioning subjects. Fast walking was associated with bilateral increases in joint excursion and muscle activation, as well as improved symmetry in some TDFs. BWS favored a hip flexion strategy in early swing while decreasing limb circumduction. Conclusions— This study shows that stroke subjects can increase substantially their walking speed without deleterious effects. Fast walking induces marked speed-related improvements in body and limb kinematics and muscle activation patterns. BWS during overground walking also increases gait speed, but to a lesser extent and only in low-functioning subjects. The combination of BWS with fast speed produces the greatest increments in walking speed in all subjects.

Speed and Temporal-Distance Adaptations during Treadmill and Overground Walking Following Stroke

Objective. To compare the maximum gait speed of stroke subjects attained during treadmill and overground in stroke subjects and to identify the temporal-distance determinants of the maximal gait speed. Methods. Ten individuals with hemiparetic gait deficits and whose walking speeds ranged between 0.24 m/s and 0.82 m/s participated. Five healthy age-matched controls were also tested to provide comparative data for the gait speed transfer between the 2 modes of locomotion. Following a brief habituation process to walking on the treadmill, subjects were tested while walking at comfortable and maximal speeds on the treadmill and overground, in a random order. Main Outcome Measure. Self-selected comfortable and maximum gait speed and temporal-distance factors were acquired using a 6-camera Vicon™ motion analysis system and compared between treadmill and overground walking at a similar speed. Results. Overground walking resulted in higher maximal speeds (P < 0.001), greater stride lengths (P < 0.001), and a lower cadence (P < 0.02), as compared to tread-mill. The comfortable gait speed and the maximum stride length proved to be strong determinants for the maximal speed on both modes of locomotion (P < 0.01), but the maximum cadence was correlated to maximum speed only for overground locomotion (P < 0.05). Conclusions. Stroke subjects walked slower on the treadmill as compared to overground. They also used a different strategy to increase gait speed, relying mostly on increasing the stride length during treadmill ambulation.

Modulation of Walking Speed by Changing Optic Flow in Persons with Stroke

The present study was undertaken to compare the modulation of walking speed in response to optic flow (OF) speed changes between persons with stroke and healthy controls. Twelve individuals with stroke and 12 healthy controls walked on a self-paced treadmill viewing a virtual corridor in a helmet-mounted display. In experiment 1, the speed of an expanding OF was varied sinusoidally at 0.017Hz, from 0 to 2 times the individuals comfortable walking speed. In experiment 2, individuals were instructed to walk through a virtual hallway of 10m at their comfortable pace (control trials). During the test trials that followed the control trials, expanding optic flows ranging from 0.25 to 1.75 of the initial comfortable speed were randomly presented. Subjects were instructed to walk the test trial distance within the same time as during the preceding control trial. Results from experiment 1 showed that gait speed was modulated out-of-phase with respect to OF speed in the healthy controls, but it varied from out-of-phase to in-phase patterns in the individuals with stroke. A negative linear relationship was observed between gait speed and OF speed in healthy and stroke individuals in experiment 2. These results indicate that individuals with stroke, although able to modulate the gait speed by changing the perception of movement through different OF speeds, present with altered modulation response patterns as compared to healthy subjects

Physiological evaluation of gait disturbances post stroke

A large proportion of stroke survivors have to deal with problems in mobility. Proper evaluations must be undertaken to understand the sensorimotor impairments underlying locomotor disorders post stroke, so that evidence-based interventions can be developed. The current electrophysiological, biomechanical, and imagery evaluations that provide insight into locomotor dysfunction post stroke, as well as their advantages and limitations, are reviewed in this paper. In particular, electrophysiological evaluations focus on the contrast of electromyographic patterns and integrity of spinal reflex pathways during perturbed and unperturbed locomotion between persons with stroke and healthy individuals. At a behavioral level, biomechanical evaluations that include temporal distance factors, kinematic and kinetic analyses, as well as the mechanical energy and metabolic cost, are useful when combined with electrophysiological measures for the interpretation of gait disturbances that are related to the control of the central nervous system or secondary to biomechanical constraints. Finally, current methods in imaging and transcranial magnetic stimulation can provide further insight into cortical control of locomotion and the integrity of the corticospinal pathways.

The effect of arm movements on the lower limb during gait after a stroke

The purpose of this study was to examine the influence of arm movements on lower limb movement and muscle activation during treadmill walking after a stroke. Ten high functioning stroke and 10 healthy subjects walked on a treadmill while swinging their arms naturally, and while holding onto handles that were either fixed in place or allowed to slide along horizontal handrails. Full-body kinematics were recorded, along with bilateral surface electromyography from lower limb muscles. Arm movements influenced lower limb muscle activity but had little effect on movement patterns at the joints. When handrails were present a small amount of weight was borne through the upper limbs, and for stroke subjects this was reduced when the handles were free to slide. Activity of proximal leg muscles during stance was affected by the weight borne through the upper limbs, increasing when arm movements were performed. Soleus activity during stance was greatest with unsupported arm movements. In stroke subjects, early stance tibialis anterior activity in the paretic leg was greatest with no arm movements, and early swing tibialis anterior activity in both legs was greatest with unsupported arm movements. Many of the changes in muscle activation appeared to be due to changes in postural stability that occurred when performing arm movements. Overall, results support further study of the long-term changes associated with the inclusion of arm movements in gait rehabilitation protocols.

The coordination of upper and lower limb movements during gait in healthy and stroke individuals.

Human walking involves coordinated movements of all four limbs. The benefits of incorporating arm movements in gait rehabilitation are not known and difficult to investigate in patient populations with poor balance and reduced walking capacity. This study assessed the effect of supported (SUP) versus unsupported (UNSUP) arm movements on the coordination patterns present during walking in individuals with and without a stroke. Ten high functioning stroke subjects and 10 healthy subjects walked on a treadmill while swinging their arms naturally, and while holding onto handles that were either fixed in place or allowed to slide along horizontal handrails. Full-body kinematics were recorded, and arm-leg coordination was quantified using relative phase index, mean relative phase, and cross-correlation of hip and shoulder angle time series. No differences were observed in any measures of coordination between healthy and stroke subjects, indicating that the ability to coordinate arm and leg movements during walking remains preserved in high functioning stroke individuals. Coordination patterns were also unaffected by the use of sliding handrails, suggesting that this paradigm may be a suitable surrogate for natural arm movements if individuals are unable to walk without an external support. Stroke subjects were able to perform arm movements at a faster walking speed when using the handles than they were able to achieve without the handles, indicating that this paradigm may be useful in encouraging arm movements during gait rehabilitation.

Gaze and Postural Reorientation in the Control of Locomotor Steering After Stroke

Background. Steering of locomotion is a complex task involving stabilizing and anticipatory orienting behavior essential for the maintenance of balance and for establishing a stable frame of reference for future motor and sensory events. How these mechanisms are affected by stroke remains unknown. Objectives. To compare locomotor steering behavior between stroke and healthy individuals and to determine whether steering abilities are influenced by walking speed, turning direction and walking capacity in stroke individuals. Methods. Gaze and body kinematics were recorded in 8 stroke and 7 healthy individuals while walking and turning in response to a visual cue. Horizontal orientation of gaze, head, thorax, pelvis, and feet with respect to spatial and heading coordinates were examined. Results. Temporal and spatial coordination of gaze and body movements revealed stabilizing and anticipatory orienting mechanisms in the healthy individuals. Changing walking speed affected the onset time but not the sequencing of segment reorientation. In the individuals with stroke, abnormally large and uncoordinated head and gaze motion were observed. The sequence of gaze, head, thorax and pelvis horizontal reorientation also was also disrupted. Alterations in orienting behaviors were more pronounced at the slowest walking speeds and turning to the nonparetic side in 3 of the most severely disabled individuals. Conclusion. The results in this convenience sample of slow and faster walkers suggest that stroke alters the stabilizing and orienting behavior during steering of locomotion. Such alterations are not caused by the inherently slow walking speed, but rather by a combination of biomechanical factors and defective sensorimotor integration, including altered vestibulo-ocular reflexes.

Efficacy of virtual reality-based intervention on balance and mobility disorders post-stroke: a scoping review.

Rehabilitation interventions involving virtual reality (VR) technology have been developed for the promotion of functional independence post stroke. A scoping review was performed to examine the efficacy of VR-based interventions on balance and mobility disorders post stroke. Twenty-four articles in the English language examining VR game-based interventions and outcomes directed at balance and mobility disorders were included. Various VR systems (customized and commercially available) were used as rehabilitation tools. Outcome measures included laboratory and clinical measures of balance and gait. Outcome measures of dynamic balance showed significant improvements following VR-based interventions as compared to other interventions. Further, it was observed that VR-based intervention may have favorable effects in improving walking speed and the ability to deal with environmental challenges, which may also facilitate independent community ambulation. VR-based therapy thus has the potential to be a useful tool for balance and gait training for stroke rehabilitation. Utilization of motor learning principles related to task-related training may have been an important factor leading to positive results. Other principles such as repetition, feedback etc. were used in studies but were not explored explicitly and may need to be investigated to further improve the strength of results. Lastly, robust study designs with appropriate attention towards the intensity and dose-response aspects of VR training, clear study objectives and suitable outcomes would further aid in determining evidence-based efficacy for VR game-based interventions in the future.

Stroke affects the coordination and stabilization of head, thorax and pelvis during voluntary horizontal head motions performed in walking

OBJECTIVE This study was conducted to investigate and compare the coordination and stabilization of axial segments during walking with and without horizontal voluntary head turns, in healthy (n=5) and hemiparetic (n=10) subjects. METHODS Subjects were instructed to turn the head as fast and as soon as possible in the direction indicated by an illuminated arrow signal (right, left or none) that was triggered at initial contact of the right (healthy) or paretic (hemiparetic) foot. Head, thorax, and pelvis motions were obtained from a 9-segment model using retro-reflective markers and a Vicon-512 system with 6 high-resolution cameras. Coordination of axial segments in the horizontal plane was characterized using cyclographs and cross-correlation analyses. Stabilization of the segments was quantified using root mean square (RMS) values of the segments normalized acceleration profile. RESULTS The healthy subjects showed a direction-dependent modulation of axial segment coordination, with head turns toward and away from the stance limb favoring and hindering, respectively, the contra-rotational pattern of the thorax with respect to the pelvis during locomotion. Meanwhile, pelvis motions remained unaltered. This direction-specific modulation pattern was disrupted in the hemiparetic subjects, both in the spatial and temporal domains. Moreover, larger RMS values for head and thorax segments were observed in the hemiparetic groups, both with and without the superimposition of voluntary head motions. CONCLUSIONS The findings suggest that: (1) head rotations during walking modify axial segment coordination in a direction-specific manner, (2) the pelvic rotations associated with locomotion remained unaffected by head rotations and (3) stroke alters this coordination behavior, which may contribute to balance dysfunctions during locomotion.

Stability of gait and interlimb coordination in older adults

Most falls in older adults occur when walking, specifically following a trip. This study investigated the short- and longer term responses of young (n = 24, 27.6 ± 4.5 yr) and older adults (n = 18, 69.1 ± 4.2 yr) to a trip during gait at comfortable speed and the role of interlimb coordination in recovery from tripping. Subjects walked on a self-paced treadmill when forward movement of their dominant leg was unexpectedly arrested for 250 ms. Recovery of center of mass (COM) movements and of double-support duration following perturbation was determined. In addition, the disruption and recovery of interlimb coordination of the arms and legs was evaluated. Although young and older subjects used similar lower limb strategies in response to the trip, older adults had less stable COM movement patterns before perturbation, had longer transient destabilization (>25%) after perturbation, required more gait cycles to recover double-support duration (older, 3.48 ± 0.7 cycles; young, 2.88 ± 0.4 cycles), and had larger phase shifts that persisted after perturbation (older, -83° to -90°; young, -39° to -42°). Older adults also had larger disruptions to interlimb coordination of the arms and legs. The timing of the initial disruption in coordination was correlated with the disturbance in gait stability only in young adults. In older adults, greater initial COM instability was related to greater longer term arm incoordination. These results suggest a relationship between interlimb coordination and gait stability, which may be associated with fall risk in older adults. Reduced coordination and gait stability suggest a need for stability-related functional training even in high-functioning older adults.