Non-paretic Leg Research Articles

A unilateral robotic knee exoskeleton to assess the role of natural gait assistance in hemiparetic patients

BackgroundHemiparetic gait is characterized by strong asymmetries that can severely affect the quality of life of stroke survivors. This type of asymmetry is due to motor deficits in the paretic leg and the resulting compensations in the nonparetic limb. In this study, we aimed to evaluate the effect of actively promoting gait symmetry in hemiparetic patients by assessing the behavior of both paretic and nonparetic lower limbs. This paper introduces the design and validation of the REFLEX prototype, a unilateral active knee–ankle–foot orthosis designed and developed to naturally assist the paretic limbs of hemiparetic patients during gait.MethodsREFLEX uses an adaptive frequency oscillator to estimate the continuous gait phase of the nonparetic limb. Based on this estimation, the device synchronically assists the paretic leg following two different control strategies: (1) replicating the movement of the nonparetic leg or (2) inducing a healthy gait pattern for the paretic leg. Technical validation of the system was implemented on three healthy subjects, while the effect of the generated assistance was assessed in three stroke patients. The effects of this assistance were evaluated in terms of interlimb symmetry with respect to spatiotemporal gait parameters such as step length or time, as well as the similarity between the joint’s motion in both legs.ResultsPreliminary results proved the feasibility of the REFLEX prototype to assist gait by reinforcing symmetry. They also pointed out that the assistance of the paretic leg resulted in a decrease in the compensatory strategies developed by the nonparetic limb to achieve a functional gait. Notably, better results were attained when the assistance was provided according to a standard healthy pattern, which initially might suppose a lower symmetry but enabled a healthier evolution of the motion of the nonparetic limb.ConclusionsThis work presents the preliminary validation of the REFLEX prototype, a unilateral knee exoskeleton for gait assistance in hemiparetic patients. The experimental results indicate that assisting the paretic leg of a hemiparetic patient based on the movement of their nonparetic leg is a valuable strategy for reducing the compensatory mechanisms developed by the nonparetic limb.

Motor control of the lower limbs while walking with the TWIN exoskeleton operated by TWINActa in healthy subjects

Lower limb exoskeletons are medical devices used in the rehabilitation to provide physical therapy to individuals with neurological disorders [1]. These robotic devices were originally designed and developed for spinal cord injury subjects, who do not have any residual walking abilities, and are therefore mainly based on an assistive approach. To successfully use these machines in subjects with residual capacities such as persons post stroke, the control system must be adapted to an assist-as- needed control scheme. This approach requires the subject active participation to stimulate the voluntary muscle contraction of the paretic limb and manage the somatosensory feedbacks subsequent to the action. For these reasons, we have developed TWINActa, a control suite for gait training following stroke, that provide asymmetric assistance to the user. The assistance-as-needed can be provided in the following modes: (i) support during the toe-off phase of the non-paretic leg; (ii) pelvic tilt damping during stance phase; (iii) stabilization of the knee joint of the supporting leg during the double support phases; and (iv) hip extension support of paretic leg during the stance phase. This study was aimed at verifying if motor control during a walking task performed with an exoskeleton, operated by TwinActa, is similar to the physiological control of walking in healthy subjects. Five healthy volunteers were asked to perform motor tasks (i.e., overground walking, stairs ascending and stair descending) wearing the TWIN exoskeleton [2] operated by TWINActa control system. During the task EMG signals were acquired from 12 muscles (10 placed on the lower limb and 2 on the upper limbs per side) and movement data were recorded from 2 IMUs placed on the shanks. Non-negative matrix factorization was carried out on the EMG recorded signal to identify muscle synergies [3]. The EMG activity patterns were also mapped onto the rostro-caudal location of ipsilateral motoneurons pools in the human spinal cord [4]. Based on the Kendall myotomal charts of segmental localization [5], we reconstructed the sacral (S1-S2) and lumbard (L2-L5) motor pool activation profiles. Pearson's correlation coefficient was used to evaluate the similarity degree of 1) muscle synergies and 2) sacral and lumbar motor pool activation profiles of walking with exoskeleton with respect to the normative reference (without device) provided by Eurobench project (Pepato scenario). Four muscle synergies accounted for a R2 > 0.85 for all participants during overground walking. A strong degree of similarity (correlation) of activation of sacral and lumbar motor pools with respect to the reference group was found (mean ± SD, 0.77 ± 0.06 and 0.78 ± 0.11, for sacral and lumbar spinal output respectively). Also the mean similarly of the muscle synergies activation profiles was strong (mean ± SD, 0.70 ± 0.14) with respect to the four physiological muscle synergies involved in gait control [6]. The four muscle synergies involved in the gait control [6] were found while walking with the exoskeleton operated by TWINActa in neurologically intact subjects. We found also a strong degree of similarity between the motor pools wearing the exoskeleton with respect to the normative reference of walking without the device. Since the spinal motor pools are associated with functional grouping of motoneurons of the lower limb muscles, our findings suggest that the Twin exoskeleton operated by TWINActa can be used as rehabilitation device to enhance the recovery of the physiological motor control in persons with residual ability. Further studies need to be conducted to verify this finding in subjects with neurological diseases.

Immediate effects of the honda walking assist on spatiotemporal gait characteristics in individuals after stroke

The use of unconstrained lower limb exoskeletons has become a promising approach to assist individuals with gait impairments. The Honda Walking Assist (HWA) is a hip-assistive exoskeleton functioning as a gait trainer and has been shown to improve several gait related outcomes after training. Studies investigating its immediate effects on spatiotemporal gait parameters other than walking speed in stroke survivors are lacking. The aim of this study was to investigate immediate differences in spatiotemporal gait parameters of stroke survivors between normal overground walking, walking with an unpowered, non-assisting HWA and walking with an optimally assisting HWA. Five ischemic stroke survivors (mean time since stroke 115 ​± ​213.6 days) walked 3 times 5 ​m in each condition. Differences in 14 spatiotemporal gait parameters between all 3 conditions were registered and reported in a descriptive manner. With optimal assistance, 4 patients walked faster (0.057–0.095 ​m/s) with longer strides of the paretic (0.055–0.069 ​m) and non-paretic (0.053–0.077 ​m) leg compared to normal walking. Compared to unpowered walking, all patients walked faster (0.020–0.063 ​m/s) in the optimal assist condition, with longer strides of the paretic (0.036–0.072 ​m) and non-paretic leg (0.045–0.082 ​m). During unpowered walking, gait velocity remained unchanged in 2 patients, increased (0.012–0.051 ​m/s) in 2 patients and decreased (−0.022 ​m/s) in 1 patient compared to normal walking. Changes in paretic stride lengths ranged from −0.066 to 0.029 ​m. The optimal individualized motor assistance provided by the HWA induces small, positive changes in gait parameters. This indicates that this light-weight hip-assistive exoskeleton can be of value in rehabilitation setting, where multiple training sessions with the device are possible.

Utility of ultrasound as a promising diagnostic tool for stroke-related sarcopenia: A retrospective pilot study.

Stroke patients undergo extensive changes in muscle mass which lead to stroke-related sarcopenia. Stroke-related sarcopenia has a significant impact on the functional outcome of stroke survivors. So, it is important to measure muscle mass in stroke patients. This study aimed to examine the correlation between ultrasonographic quadriceps muscle thickness (QMT) and dual-energy X-ray absorptiometry (DXA) derived appendicular lean mass (ALM) in patients with acute hemiplegic stroke. Twenty five participants were included (13 men and 12 women) in this study, who were diagnosed with stroke within 1 month. For both paretic and non-paretic legs, QMT was measured by an ultrasound and ALM was obtained by performing DXA scan. We analyzed the difference and the correlation between ultrasonographic QMT and DXA-derived lean body mass of both paretic and non-paretic legs. Stroke patients were divided into 2 groups according to the paretic knee extensor power. Ultrasonographic QMT, DXA scan findings, and functional parameters were compared. There was a significant correlation between QMT and ALM index, and between QMT and site-specific lean mass (SSLM) of both the legs for both the sexes (P < .05). In multivariate linear regression model, we made adjustments for the confounding factors of age, sex, body mass index (BMI) and paretic knee extensor power. We observed a positive relationship between QMT and ALM index (P < .05), and between QMT and SSLM of both the legs (P < .05). The % QMT showed higher difference than % SSLM between paretic and non-paretic legs (10.25% vs 4.58%). The QMT measurements of ultrasound show a great relationship with DXA scan findings. Ultrasound better reflects the change of muscle mass between paretic and non-paretic legs than DXA scan at an acute phase of stroke. Ultrasound could be a useful tool to evaluate stroke-related sarcopenia.

The effects of stroke on weight transfer before voluntary lateral and forward steps.

There is a higher rate of falls in the first year after a stroke, and the ability to step in different directions is essential for avoiding a fall and navigating small spaces where falls commonly occur. The lateral transfer of weight is important for stabilizing the body before initiating a step. Hence, understanding the ability to control lateral weight transfer (WT) in different step directions might help understand falls in individuals with stroke. The present study aimed to compare the WT characteristics (onset time, duration, mediolateral center of pressure (ML COP) velocity, and ML COP displacement) and hip abduction torque preceding a lateral and forward voluntary step between individuals with stroke (paretic and non-paretic leg) and controls. Twenty individuals with stroke and ten controls performed voluntary choice reaction tests in the lateral and forward directions. Ten trials (five on each side—right and left) were performed for each step direction. The overall primary findings were that (1) the WT before a lateral step was shorter and initiated earlier, with a larger ML COP displacement and greater hip abductor torque in the stepping leg than the forward step, (2) there was greater hip abductor produced in the stance leg before a forward step than a lateral step, (3) the WT before the lateral step took longer to initiate and was slower to execute in individuals with stroke regardless of the leg (4) the WT before the forward step had more differences in the paretic than the non-paretic leg. Thus, for the first time, it was shown that the WT characteristics and hip abduction torque during the WT are different according to step direction and also appear to be impaired in individuals with stroke. These results have implications for understanding the direction that individuals with stroke are more susceptible to being unable to recover balance and are at risk of falling.

Motor overflow in the lower limb after stroke: Insights into mechanisms.

Motor overflow (involuntary muscle activation) is common after stroke, particularly in the non-paretic upper limb. Two potential cortical mechanisms are as follows: (1) The contralesional hemisphere controls both limbs, and (2) inhibition from the ipsilesional to the contralesional hemisphere is diminished. Few studies have differentiated between these hypotheses or investigated motor overflow in the lower limb after stroke. To investigate these potential mechanisms, individuals with chronic stroke performed unilateral isometric and dynamic dorsiflexion. Motor overflow was quantified in the contralateral, resting (non-target) ankle. Transcranial magnetic stimulation (TMS) was applied, and responses were measured in both legs. Relations between motor overflow, excitability of ipsilateral motor pathways, and interhemispheric inhibition were assessed. Non-target muscle activity (motor overflow) was greater during isometric and dynamic conditions than rest in both legs (p≤0.001) and was higher in the non-paretic than the paretic leg (p= 0.03). Some participants (25%) had motor overflow >4SD above the group mean in the non-paretic leg. Greater motor overflow in the non-paretic leg was associated with lesser inhibition from the ipsilesional to the contralesional hemisphere (p= 0.04). In both legs, non-target TMS responses were greater during the isometric and dynamic than the rest condition (p≤0.01) but not when normalized to background muscle activity. Overall, motor overflow occurred in both legs after stroke, suggesting a common bilateral mechanism. Our correlational results suggest that alterations in interhemispheric inhibition may contribute to motor overflow. Furthermore, the lack of differences in non-target motor evoked potentials MEPs between rest, isometric, and dynamic conditions suggests that subcortical and/or spinal pathways may contribute to motor overflow.

Muscle contributions to pre-swing biomechanical tasks influence swing leg mechanics in individuals post-stroke during walking

BackgroundSuccessful walking requires the execution of the pre-swing biomechanical tasks of body propulsion and leg swing initiation, which are often impaired post-stroke. While excess rectus femoris activity during swing is often associated with low knee flexion, previous work has suggested that deficits in propulsion and leg swing initiation may also contribute. The purpose of this study was to determine underlying causes of propulsion, leg swing initiation and knee flexion deficits in pre-swing and their link to stiff knee gait in individuals post-stroke.MethodsMusculoskeletal models and forward dynamic simulations were developed for individuals post-stroke (n = 15) and healthy participants (n = 5). Linear regressions were used to evaluate the relationships between peak knee flexion, braking and propulsion symmetry, and individual muscle contributions to braking, propulsion, knee flexion in pre-swing, and leg swing initiation.ResultsFour out of fifteen of individuals post-stroke had higher plantarflexor contributions to propulsion and seven out of fifteen had higher vasti contributions to braking on their paretic leg relative to their nonparetic leg. Higher gastrocnemius contributions to propulsion predicted paretic propulsion symmetry (p = 0.005) while soleus contributions did not. Higher vasti contributions to braking in pre-swing predicted lower knee flexion (p = 0.022). The rectus femoris had minimal contributions to lower knee flexion acceleration in pre-swing compared to contributions from the vasti. However, for some individuals with low knee flexion, during pre-swing the rectus femoris absorbed more power and the iliopsoas contributed less power to the paretic leg. Total musculotendon work done on the paretic leg in pre-swing did not predict knee flexion during swing.ConclusionsThese results emphasize the multiple causes of propulsion asymmetry in individuals post-stroke, including low plantarflexor contributions to propulsion, increased vasti contributions to braking and reliance on compensatory mechanisms. The results also show that the rectus femoris is not a major contributor to knee flexion in pre-swing, but absorbs more power from the paretic leg in pre-swing in some individuals with stiff knee gait. These results highlight the need to identify individual causes of propulsion and knee flexion deficits to design more effective rehabilitation strategies.

Timing of propulsion-related biomechanical variables is impaired in individuals with post-stroke hemiparesis

BackgroundIn individuals with post-stroke hemiparesis, reduced paretic leg propulsion, measured through anterior ground reaction forces (AGRF), is a common and functionally-relevant gait impairment. Deficits in other biomechanical variables such as plantarflexor moment, ankle power, and ankle excursion contribute to reduced propulsion. While reduction in the magnitude of propulsion post-stroke is well studied, here, our objective was to compare the timing of propulsion-related biomechanical variables. Research questionAre there differences in the timing of propulsion and propulsion-related biomechanical variables between able-bodied individuals, the paretic leg, and non-paretic leg of post-stroke individuals? MethodsNine able-bodied and 13 post-stroke individuals completed a gait analysis session comprising treadmill walking trials at each participant’s self-selected speed. Two planned independent sample t-tests were conducted to detect differences in the timing of dependent variables between the paretic versus non-paretic leg post-stroke and paretic leg versus the dominant leg of able-bodied individuals. ResultsPost-stroke individuals demonstrated significantly earlier timing of peak AGRF of their paretic leg versus their non-paretic leg and able-bodied individuals. Post-stroke participants displayed earlier timing of peak power of their paretic leg versus their non-paretic leg and able-bodied individuals, and earlier timing of peak ankle moment of the paretic leg versus able-bodied. No significant differences were detected in the timing of peak ankle angle. SignificanceThe earlier onset of peak AGRF, peak ankle power, and peak ankle moment may be an important, under-studied biomechanical factor underlying stroke gait impairments, and a potential therapeutic target for stroke gait retraining. Future investigations can explore the use of interventions such as gait biofeedback to normalize the timing of these peaks, thereby improving propulsion and walking function post-stroke.

Differences in mediolateral dynamic stability during gait initiation according to whether the non-paretic or paretic leg is used as the leading limb.

We investigated mediolateral dynamic stability at first foot off and first initial contact during gait initiation according to whether the paretic or non-paretic leg was used as the leading limb. Thirty-eight individuals with stroke initiated gait with the paretic and non-paretic legs as the leading limb, and their movements were measured using a 3D motion analysis system. Margin of stability (i.e., the length between the extrapolated center of mass and lateral border of the stance foot) was used as an index of dynamic stability, with a large value indicating dynamic stability in the lateral direction. However, an excessively large margin of stability value (i.e., when the extrapolated center of mass is outside the medial border of the stance foot) indicates dynamic instability in the medial direction. Differences in the margin of stability between tasks were compared using the Wilcoxon signed-rank test. The minimum margin of stability was observed just before first foot off. When the non-paretic leg was used as the leading limb, the margin of stability tended to be excessively large at first foot off compared with when the paretic leg was used (p < 0.001). In other words, the extrapolated center of mass was outside the medial border of the paretic stance foot. In conclusion, lateral stability was achieved when using the non-paretic leading limb because the extrapolated center of mass was located outside the medial border of the stance foot. However, medial dynamic stability was lower for the non-paretic leading limb compared with the paretic leading limb.

Differences in paretic lower limb loading and fluidity in sit-to-walk according to selection of the leading limb in individuals with stroke

BackgroundSit-to-walk is an asymmetric task that is challenging for individuals with stroke, and paretic limb loading at seat-off and movement fluidity may change according to whether the non-paretic or paretic leg is used as the leading limb. This study aimed to investigate differences in paretic limb loading and fluidity depending on whether the non-paretic limb or paretic limb was used as the leading limb. MethodsThirty-eight individuals with stroke performed sit-to-walk with each leg as the leading limb, and their movements were measured using a 3D motion analysis system. The paired t-test or Wilcoxon signed-rank test was used to assess differences according to limb selection in paretic limb loading ratio at seat-off and fluidity (Fluidity Index: ratio of the lowest to peak forward velocity before first initial contact). FindingsTwenty-two of 38 participants preferred to use the paretic limb as the leading limb. When leading with the paretic limb, the paretic limb loading ratio was significantly larger (p = 0.002), and the Fluidity Index was lower (p = 0.007). InterpretationSit-to-walk with the paretic leading limb seems to be an adaptive movement because many participants preferred leading with the paretic limb. However, selection of the leading limb in sit-to-walk involves a biomechanical tradeoff between paretic limb loading at seat-off and movement fluidity in individuals with stroke. Use of the paretic leading limb requires loading capacity of this limb, and the non-paretic leading limb must have high balance ability to merge sit-to-stand and gait initiation.

Lower limb muscle performance during a closed chain single leg squat and a squat jump in people with leg weakness after stroke: A comparative study

Abstract Objective: To determine if the intention to perform an exercise at speed leads to beneficial alterations in kinematic and kinetic components of the movement in people with post-stroke hemiplegia. Design: Comparative study. Setting: Subacute metropolitan rehabilitation hospital. Participants: Convenience sample of patients admitted as an inpatient or outpatient with a diagnosis of stroke with lower limb weakness, functional ambulation category score ≥3, and ability to walk ≥14metres. Methods: Participants performed a single leg squat exercise on their paretic and nonparetic legs on a leg sled under three conditions: 1) self-selected speed (SS), 2) fast speed (FS), 3) jump squat (JS). Measures of displacement, flight time, peak concentric velocity, and muscle excitation (via electromyography) were compared between legs and conditions. Results: Eleven participants (age: 56 ± 17 years; median time since stroke onset: 3.3 [IQR 3,41] months) were tested. All participants achieved a jump during the JS, as measured by displacement and flight time respectively, on both their paretic (0.25 ± 0.16 m and 0.42 ± 0.18 s) and nonparetic (0.49 ± 0.36 m and 0.73 ± 0.28 s) legs; however it was significantly lower on the non-paretic leg (p &lt; 0.05). Peak concentric velocity increased concordantly with intended movement speed (JS-FS paretic: 0.96 m/s, non-paretic: 0.54 m/s; FS-SS paretic 0.69 m/s, nonparetic 0.38 m/s; JS-SS paretic 1.66 m/s, non-paretic 0.92 m/s). Similarly, muscle excitation increased significantly (p &lt; 0.05) with faster speed for the paretic and nonparetic vastus lateralis. For gastrocnemius, the only significant difference was an increase during nonparetic JS vs. SS and FS. Conclusions: Speed affects the kinematic and kinetic components of the movement. Performing exercises ballistically may improve training outcomes for people post-stroke.

Lower limb muscle performance during a closed chain single leg squat and a squat jump in people with leg weakness after stroke: A comparative study

Objective: To determine if the intention to perform an exercise at speed leads to beneficial alterations in kinematic and kinetic components of the movement in people with post-stroke hemiplegia. Design: Comparative study. Setting: Subacute metropolitan rehabilitation hospital. Participants: Convenience sample of patients admitted as an inpatient or outpatient with a diagnosis of stroke with lower limb weakness, functional ambulation category score ≥3, and ability to walk ≥14metres. Methods: Participants performed a single leg squat exercise on their paretic and nonparetic legs on a leg sled under three conditions: 1) self-selected speed (SS), 2) fast speed (FS), 3) jump squat (JS). Measures of displacement, flight time, peak concentric velocity, and muscle excitation (via electromyography) were compared between legs and conditions. Results: Eleven participants (age: 56 ± 17 years; median time since stroke onset: 3.3 [IQR 3,41] months) were tested. All participants achieved a jump during the JS, as measured by displacement and flight time respectively, on both their paretic (0.25 ± 0.16 m and 0.42 ± 0.18 s) and nonparetic (0.49 ± 0.36 m and 0.73 ± 0.28 s) legs; however it was significantly lower on the non-paretic leg (p &lt; 0.05). Peak concentric velocity increased concordantly with intended movement speed (JS-FS paretic: 0.96 m/s, non-paretic: 0.54 m/s; FS-SS paretic 0.69 m/s, nonparetic 0.38 m/s; JS-SS paretic 1.66 m/s, non-paretic 0.92 m/s). Similarly, muscle excitation increased significantly (p &lt; 0.05) with faster speed for the paretic and nonparetic vastus lateralis. For gastrocnemius, the only significant difference was an increase during nonparetic JS vs. SS and FS. Conclusions: Speed affects the kinematic and kinetic components of the movement. Performing exercises ballistically may improve training outcomes for people post-stroke.

Does the stimulus provoking a stepping reaction correlate with step characteristics and clinical measures of balance and mobility post-stroke?

BackgroundRetraining stepping reactions in people post-stroke is vital. However, the relationship between the stimulus and resulting stepping performance in people post-stroke is unknown. We explored relationships between stepping stimulus and stepping reactions initiated by either paretic or non-paretic legs of people post-stroke and controls. Relationships were examined in the context of clinical measures of balance. MethodsCentre of mass dynamics were measured during self-initiated destabilizing leaning stimuli that required stepping reactions by paretic and non-paretic legs of people post-stroke (n = 10) and controls (n = 10) to recover balance. Step characteristics of the first two steps of stepping reactions were measured. Correlations were calculated between clinical measures of balance and mobility and the centre of mass and step characteristics. FindingsSteps were shorter and slower with decreased centre of mass fore-aft and downward displacement and velocity when initiated by paretic and non-paretic legs compared with controls. However, increase in centre of mass displacement and velocity in the fore-aft and downward direction tended to be associated with a greater increase in step length and speed when stepping reactions were initiated by the paretic and non-paretic legs compared with controls. Time to step initiation in response to onset of falling stimulus did not differ between groups. Strong positive correlations were found between clinical balance and mobility scores and centre of mass and step dynamics in fore-aft and vertical directions. InterpretationThese results support objective measurement of centre of mass to quantify the stimulus influencing step dynamics and stepping performance during retraining interventions following stroke.

Lower limb muscle performance during a closed chain single leg squat and a squat jump in people with leg weakness after stroke: A comparative study

Objective: To determine if the intention to perform an exercise at speed leads to beneficial alterations in kinematic and kinetic components of the movement in people with post-stroke hemiplegia. Design: Comparative study. Setting: Subacute metropolitan rehabilitation hospital. Participants: Convenience sample of patients admitted as an inpatient or outpatient with a diagnosis of stroke with lower limb weakness, functional ambulation category score ≥3, and ability to walk ≥14metres. Methods: Participants performed a single leg squat exercise on their paretic and nonparetic legs on a leg sled under three conditions: 1) self-selected speed (SS), 2) fast speed (FS), 3) jump squat (JS). Measures of displacement, flight time, peak concentric velocity, and muscle excitation (via electromyography) were compared between legs and conditions. Results: Eleven participants (age: 56 ± 17 years; median time since stroke onset: 3.3 [IQR 3,41] months) were tested. All participants achieved a jump during the JS, as measured by displacement and flight time respectively, on both their paretic (0.25 ± 0.16 m and 0.42 ± 0.18 s) and nonparetic (0.49 ± 0.36 m and 0.73 ± 0.28 s) legs; however it was significantly lower on the non-paretic leg (p &lt; 0.05). Peak concentric velocity increased concordantly with intended movement speed (JS-FS paretic: 0.96 m/s, non-paretic: 0.54 m/s; FS-SS paretic 0.69 m/s, nonparetic 0.38 m/s; JS-SS paretic 1.66 m/s, non-paretic 0.92 m/s). Similarly, muscle excitation increased significantly (p &lt; 0.05) with faster speed for the paretic and nonparetic vastus lateralis. For gastrocnemius, the only significant difference was an increase during nonparetic JS vs. SS and FS. Conclusions: Speed affects the kinematic and kinetic components of the movement. Performing exercises ballistically may improve training outcomes for people post-stroke.

Muscle Oxygenation of the Paretic and Nonparetic Legs During and After Arterial Occlusion in Chronic Stroke

Oxygen delivery and demand are reduced in the paretic leg post-stroke, reflecting decreased vascular function and reduced muscle quantity and quality. However, it is unknown how muscle oxygenation, the balance between muscle oxygen delivery and utilization, is altered in chronic stroke during and after occlusion-induced ischemia. ObjectivesThe objective was to determine muscle oxygen consumption rate, microvascular responsiveness and reactive hyperemia in the paretic and nonparetic legs during and after arterial occlusion post-stroke. Materials and MethodsMuscle oxygen saturation was measured with near-infrared spectroscopy on the vastus lateralis of each leg during 3-minute arterial occlusion and recovery (3 min). Muscle oxygen consumption was derived from the desaturation slope during ischemia, microvascular responsiveness was derived from the resaturation slope after ischemia and reactive hyperemia was derived from the area under the curve above baseline after ischemia. Results: Eleven subjects (91% male; 32.2±6.1 months post-stroke; age 62.9±13.6 years) with a hemiparetic gait pattern participated. There was no significant between-leg muscle oxygenation difference at rest (paretic: 64.9±16.6%; nonparetic: 70.6±15.6%, p = 0.13). Muscle oxygen consumption in the paretic leg (-0.53±0.24%/s) was significantly reduced compared to the nonparetic leg (-0.70±0.36%/s; p = 0.03). Microvascular responsiveness was significantly reduced in the paretic leg compared to the nonparetic leg (paretic: 4.6±1.8%/s; nonparetic: 5.7±1.6%/s, p = 0.04). Reactive hyperemia was not significantly different between legs (paretic:4384±2341%·s; nonparetic: 3040±2216%·s, p = 0.07). ConclusionMuscle oxygen consumption and microvascular responsiveness are impaired in the paretic compared to the nonparetic leg, suggesting both reduced skeletal muscle aerobic function and reduced ability to maximally perfuse muscle tissue.

The gait profile score characterises walking performance impairments in young stroke survivors

BackgroundThe Gait Profile Score (GPS) provides a composite measure of the quality of joint movement during walking, but the relationship between this measure and metabolic cost, temporal (e.g. walking speed) and spatial (e.g. stride length) parameters in stroke survivors has not been reported.Research Question: The aims of this study were to compare the GPS (paretic, non-paretic, and overall score) of young stroke survivors to the healthy able-bodied control and determine the relationship between the GPS and metabolic cost, temporal (walking speed, stance time asymmetry) and spatial (stride length, stride width, step length asymmetry) parameters in young stroke survivors to understand whether the quality of walking affects walking performance in stroke survivors. MethodsThirty-nine young stroke survivors aged between 18 and 65years and 15 healthy age-matched able-bodied controls were recruited from six hospital sites in Wales, UK. Joint range of motion at the pelvis, hip, knee and ankle, and temporal and spatial parameters were measured during walking on level ground at self-selected speed with calculation of the Gait Variable Score and then the GPS. ResultsGPS for the paretic leg (9.40° (8.60–10.21) p < 0.001), non-paretic leg (11.42° (10.20–12.63) p < 0.001) and overall score (11.18° (10.26–12.09) p < 0.001)) for stroke survivors were significantly higher than the control (4.25° (3.40–5.10), 5.92° (5.11 (6.73)). All parameters with the exception of step length symmetry ratio correlated moderate to highly with the GPS for the paretic, non-paretic, and/or overall score (ρ = <−0.732 (p < 0.001)). SignificanceThe quality of joint movement during walking measured via the GPS is directly related to the speed and efficiency of walking, temporal (stance time symmetry) and spatial (stride length, stride width) parameters in young stroke survivors.

Insights into motor performance deficits after stroke: an automated and refined analysis of the lower-extremity motor coordination test (LEMOCOT)

BackgroundThe lower-extremity motor coordination test (LEMOCOT) is a performance-based measure used to assess motor coordination deficits after stroke. We aimed to automatically quantify performance on the LEMOCOT and to extract additional performance parameters based on error analysis in persons with stroke (PwS) and healthy controls. We also aimed to explore whether these parameters provide additional information regarding motor control deficit that is not captured by the traditional LEMOCOT score. In addition, the associations between the LEMOCOT score, parameters of error and performance-based measures of lower-extremity impairment and gait were tested.MethodsTwenty PwS (age: 62 ± 11.8 years, time after stroke onset: 84 ± 83 days; lower extremity Fugl-Meyer: 30.2 ± 3.7) and 20 healthy controls (age: 42 ± 15.8 years) participated in this cross-sectional exploratory study. Participants were instructed to move their big toe as fast and accurately as possible between targets marked on an electronic mat equipped with force sensors (Zebris FDM-T, 60 Hz). We extracted the contact surface area of each touch, from which the endpoint location, the center of pressure (COP), and the distance between them were computed. In addition, the absolute and variable error were calculated.ResultsPwS touched the targets with greater foot surface and demonstrated a greater distance between the endpoint location and the location of the COP. After controlling for the number of in-target touches, greater absolute and variable errors of the endpoint were observed in the paretic leg than in the non-paretic leg and the legs of controls. Also, the COP variable error differentiated between the paretic, non-paretic, and control legs and this parameter was independent of in-target counts. Negative correlations with moderate effect size were found between the Fugl Meyer assessment and the error parameters.ConclusionsPwS demonstrated lower performance in all outcome measures than did controls. Several parameters of error indicated differences between legs (paretic leg, non-paretic leg and controls) and were independent of in-target touch counts, suggesting they may reflect motor deficits that are not identified by the traditional LEMOCOT score.

Kinect-based rapid movement training to improve balance recovery for stroke fall prevention: a randomized controlled trial

BackgroundFalls are more prevalent in stroke survivors than age-matched healthy older adults because of their functional impairment. Rapid balance recovery reaction with adequate range-of-motion and fast response and movement time are crucial to minimize fall risk and prevent serious injurious falls when postural disturbances occur. A Kinect-based Rapid Movement Training (RMT) program was developed to provide real-time feedback to promote faster and larger arm reaching and leg stepping distances toward targets in 22 different directions.ObjectiveTo evaluate the effectiveness of the interactive RMT and Conventional Balance Training (CBT) on chronic stroke survivors’ overall balance and balance recovery reaction.MethodsIn this assessor-blinded randomized controlled trial, chronic stroke survivors were randomized to receive twenty training sessions (60-min each) of either RMT or CBT. Pre- and post-training assessments included clinical tests, as well as kinematic measurements and electromyography during simulated forward fall through a “lean-and-release” perturbation system.ResultsThirty participants were recruited (RMT = 16, CBT = 14). RMT led to significant improvement in balance control (Berg Balance Scale: pre = 49.13, post = 52.75; P = .001), gait control (Timed-Up-and-Go Test: pre = 14.66 s, post = 12.62 s; P = .011), and motor functions (Fugl-Meyer Assessment of Motor Recovery: pre = 60.63, post = 65.19; P = .015), which matched the effectiveness of CBT. Both groups preferred to use their non-paretic leg to take the initial step to restore stability, and their stepping leg’s rectus femoris reacted significantly faster post-training (P = .036).ConclusionThe RMT was as effective as conventional balance training to provide beneficial effects on chronic stroke survivors’ overall balance, motor function and improving balance recovery with faster muscle response.Trial registration: The study was registered at Clinicaltrials.gov (https://clinicaltrials.gov/ct2/show/NCT03183635, NCT03183635) on 12 June 2017.

MUSCLE OXYGENATION BETWEEN THE PARETIC AND NONPARETIC LEG MEASURED DURING ARTERIAL OCCLUSION AND EXERCISE IN CHRONIC STROKE

<h3>BACKGROUND</h3> Oxygen delivery and demand are reduced in the paretic leg of individuals post-stroke, reflecting decreases of vascular function and reductions of muscle quantity and quality. However, it is unknown how muscle oxygenation, the balance between delivery and utilization of oxygen, at the muscle is altered post-stroke and how it relates to functional ambulation and aerobic exercise. The purpose of this study was to determine the difference in muscle oxygenation between the paretic and nonparetic leg of post-stroke individuals and determine if there is an association with the six-minute walk test (6MWT) distance. <h3>METHODS AND RESULTS</h3> This was a single group cross-sectional study and a sub-study of a larger two-arm parallel-group superiority trial. Skeletal muscle O2 saturation (SMO2) of the paretic and nonparetic vastus lateralis muscles were monitored continuously with two near-infrared spectroscopy (NIRS) devices, a non-invasive measure of muscle oxygenation. NIRS outcomes were measured at rest, during arterial occlusion, acute submaximal exercise and 6MWT. Muscle oxygenation was evaluated by the rate of SMO2 deoxygenation and reoxygenation during and after occlusion and exercise, and by SMO2 averages for rest and the 6MWT (see figure). Eleven subjects (91% male; 32.2±6.1 months post-stroke; age 62.9±13.6 years, with a Chedoke–McMaster Stroke Assessment score of 4.1±1.4 of the paretic leg; 7 representing normal movement) participated. There was no significant difference in SMO2 between legs at rest (p=0.13) or during the 6MWT (p=0.26). The arterial occlusion desaturation slope in the nonparetic leg (-0.70±0.36%/second) was significantly steeper than the paretic leg (-0.53±0.24%/second; p=0.03), suggesting impaired oxygen consumption in the paretic leg. The post-occlusion resaturation slope was significantly steeper in the nonparetic leg (5.7±1.6%/second) compared to the paretic leg (4.6±1.8%/second; p=0.04), indicating poorer microvascular function in the paretic leg. The exercise deoxygenation slope in the paretic leg (-0.6±0.6%/second) was significantly steeper than the non-paretic leg (-0.3±0.2%/second; p=0.047), indicating a greater mismatch between oxygen delivery and consumption at the onset of exercise, however, there was no significant difference between legs in the post-exercise resaturation slope (p=0.39). Average 6MWT SMO2 of each leg was not significantly correlated with 6MWT distance (Paretic: r=-0.06, p=0.85; Nonparetic: r=0.25, p=0.46). <h3>CONCLUSION</h3> Oxygen consumption and microvascular responsiveness are reduced in the paretic compared to the nonparetic leg. At the onset of exercise there is a mismatch between oxygen delivery and consumption in the paretic leg, which may require strategies to improve muscle oxygenation in this population.

The effect of virtual reality environment on spatial-temporal gait parameters during self-paced treadmill walking

A common measure of rehabilitation effectiveness post-stroke is self-selected walking speed, yet individuals may achieve the same speed using different coordination strategies. Asymmetry in the propulsion generated by each leg can provide insight into paretic leg coordination due to its relatively strong correlation with hemiparetic severity. Subjects walking at the same speed can exhibit different propulsion asymmetries, with some subjects relying more on the paretic leg and others on the nonparetic leg. The goal of this study was to assess whether analyzing propulsion asymmetry can help distinguish between improved paretic leg coordination versus nonparetic leg compensation.Three-dimensional forward dynamics simulations were developed for two post-stroke hemiparetic subjects walking at identical speeds before/after rehabilitation with opposite changes in propulsion asymmetry. Changes in the individual muscle contributions to forward propulsion were examined.The major source of increased forward propulsion in both subjects was from the ankle plantarflexors. How they were utilized differed and appears related to changes in propulsion asymmetry. Subject A increased propulsion generated from the paretic plantarflexors, while Subject B increased propulsion generated from the nonparetic plantarflexors. Each subject's strategy to increase speed also included differences in other muscle groups (e.g., hamstrings) that did not appear to be related to propulsion asymmetry.The results of this study highlight how speed cannot be used to elucidate underlying muscle coordination changes following rehabilitation. In contrast, propulsion asymmetry appears to provide insight into changes in plantarflexor output affecting propulsion generation and may be useful in monitoring rehabilitation outcomes.