Non-paretic Leg Research Articles

Differences in self-selected and fastest-comfortable walking in post-stroke hemiparetic persons

Post-stroke hemiparetic walking is typically asymmetric. Assessment of symmetry is often performed at either self-selected or fastest-comfortable walking speeds to gain insight into coordination deficits and compensatory mechanisms. However, how walking speed influences the level of asymmetry is unclear. This study analyzed relative changes in paretic and non-paretic leg symmetry to assess whether one speed is more effective at highlighting asymmetries in hemiparetic walking and whether there is a systematic effect of speed on asymmetry. Forty-six subjects with chronic hemiparesis walked at their self-selected and fastest-comfortable speeds on an instrumented split-belt treadmill. Relative proportions (paretic leg value/(paretic + non-paretic leg value)) were computed at each speed for step length (PSR), propulsion (PP), and joint moment impulses at the ankle and hip. Thirty-six subjects did not change their step length symmetry with speed, while three subjects changed their step length values toward increased asymmetry and seven changed toward increased symmetry. Propulsion symmetry did not change uniformly with speed for the group, with 15 subjects changing their propulsion values toward increased asymmetry while increasing speed from their self-selected to fastest-comfortable and 11 decreasing the asymmetry. Both step length and propulsion symmetry were correlated with ankle impulse proportion at self-selected and fastest-comfortable speed (cf., hip impulse proportion), but ratios (self-selected value/fastest-comfortable value) of the proportion measures (PSR and PP) showed that neither step length nor propulsion symmetry correlated with the ankle impulse proportions. Thus, the individual kinetic mechanisms used to increase speed could not be predicted from PSR or PP.

Measurement of Paretic–Lower-Extremity Loading and Weight Transfer After Stroke

Weight bearing through, or "loading" of, the paretic lower extremity and transfer of weight from one lower extremity to the other are important impairment-level goals of stroke rehabilitation. Improvements in these limb-loading and weight-transfer abilities have been shown to relate to improved performance of many functional activities. Unfortunately, valid and practical clinical measures of paretic-lower-extremity loading and weight transfer have not been identified. The purpose of this study was to assess convergent validity of the Step Test (ST) and the knee extension component of the Upright Motor Control Test (UMCe) as measures of paretic-limb loading and of the Repetitive Reach Test (RR) as a measure of weight transfer in the first 6 months after stroke. This was a prospective cohort study of 33 adults with lower-extremity motor impairment following unilateral, noncerebellar stroke. Participants were tested one time per month from 1 to 6 months poststroke. Scores on the ST (performed with the nonparetic leg as the stepping leg) and UMCe were positively correlated with peak vertical ground reaction forces (GRFs) beneath the paretic limb during functional tasks (R(2)=.35-.76 for the ST, pseudo R(2)=.21-.34 for the UMCe). Scores on the RR were positively correlated with change in vertical GRF beneath the paretic limb during the diagonal reach task (R(2)=.45) and with weight-transfer time during stepping with the nonparetic limb (R(2)=.15). The ST, performed with the nonparetic leg as the stepping leg, is a valid measure of paretic-limb loading during stroke recovery. Of the clinical measures tested, the ST correlated most strongly with the force platform measures.

Voluntary Activation of the Knee Extensors in Chronic Poststroke Subjects

To assess the extent to which knee extensor muscle weakness in subjects with chronic mild to moderate poststroke hemiparesis is caused by a decreased voluntary activation. Forty community dwelling and ambulant men and women (mean age, 59.8 +/- 5.5 yrs) with residual hemiparesis (19.2 +/- 8.5 mos poststroke) were tested. Torque measurements were performed on a computerized dynamometer and the superimposed electrical stimulation technique was used to assess voluntary activation of the knee extensors in both the paretic and the nonparetic lower limbs. The mean voluntary activation ratio of the knee extensors in the nonparetic and paretic leg was 0.97 +/- 0.04 and 0.86 +/- 0.13, respectively. Subjects who had a greater relative weakness, implying a more pronounced poststroke impairment, also had lower voluntary activation ratios. The mean percentage difference in total torque between the nonparetic and the paretic knee extensors after the electrical stimulation was 36.4% +/- 17.0%. Paretic knee extensor muscle weakness in chronic poststroke subjects is only partially explained by a reduced voluntary activation ability, indicating that other neuromuscular structural or functional factors contribute to poststroke hemiparetic muscle weakness.

Isometric Muscle Function of Knee Extensors and the Relation With Functional Performance in Patients With Stroke

Gerrits KH, Beltman MJ, Koppe PA, Konijnenbelt H, Elich PD, de Haan A, Janssen TW. Isometric muscle function of knee extensors and the relation with functional performance in patients with stroke. Objective (1) To examine the isometric strength, speed, and fatigue resistance of the knee extensors of the paretic limb and nonparetic limb in patients with stroke and compare these with able-bodied subjects. (2) To relate the contractile properties with different indices of functional performance. Design Case-control study. Setting Rehabilitation center research laboratory. Participants Eighteen stroke patients and 10 able-bodied controls. Interventions Not applicable. Main Outcome Measures Maximal voluntary torque (MVT), maximal rate of torque development, time to maximal rate of torque development, half relaxation time (½RT), and fatigue index. Scores on the Functional Ambulation Category scale, Berg Balance Scale, and Rivermead Mobility Index as well as distance walked during the six-minute walk test were obtained. Results MVT of the paretic leg was lower than of the nonparetic leg ( P<.05), and both limbs had lower MVT than controls ( P<.05). Both the paretic and the nonparetic leg showed longer ½RT compared with controls ( P<.05). The fatigue index was reduced in the paretic leg ( P<.05) but not in the nonparetic leg compared with controls. MVT and fatigue index of the paretic leg were related to indices of functional performance ( r=0.49–0.64; P<.05). Conclusions Apart from bilateral weakness, knee extensors in patients with stroke showed a lower rate of torque development and relaxation (both paretic and nonparetic leg) and lower fatigue resistance (paretic leg only) than controls, which in part may be a consequence of changes within the muscles. Strength and fatigue resistance relate to functional performance, indicating that these muscle properties should be addressed during rehabilitation. However, future research is needed to elucidate the efficacy of exercise programs.

Design of optimal profiles of electrical stimulation for restoring of the walking

We present a method for the synthesis of electrical stimulation profiles for assisting of the walking in hemiplegic individuals. The stimulation profiles are synthesized by combining the joint torques estimated from the simulation that optimizes the tracking errors with a constraint of the minimal coactivation of antagonist muscles and the recruitment of the muscles for the potential user. The predicted electrical stimulation profiles were compared with the EMG recordings of the prime movers of the leg joints. The conclusion is that synthesis of controls should rely on muscle activation profiles determined through simulation, in which the level of coactivation of antagonist muscles are preset to ensure stability of the joints and smooth movements. The example presented uses data from a healthy individual (model parameters), but the methodology is directly implantable for hemiplegic individual just by replacing the model parameters, the EMG and the trajectory of the nonparetic leg.

Human genome comparison of paretic and nonparetic vastus lateralis muscle in patients with hemiparetic stroke

Hemiparetic stroke leads to major skeletal muscle abnormalities, as illustrated by paretic leg atrophy, weakness, and spasticity. Furthermore, the hemiparetic limb muscle shifts to a fast-twitch muscle fiber phenotype with anaerobic metabolism. This study investigated whether skeletal muscle genes were altered in chronic hemiparetic stroke. The nonparetic leg muscle served as an internal control. We used Affymetrix microarray analysis to survey gene expression differences between paretic and nonparetic vastus lateralis muscle punch biopsies from 10 subjects with chronic hemiparetic stroke. Stroke latency was greater than 6 months. We found that 116 genes were significantly altered between the paretic and non paretic vastus lateralis muscles. These gene differences were consistent with reported differences after stroke in areas such as injury and inflammation markers, the myosin heavy chain profile, and high prevalence of impaired glucose tolerance and type 2 diabetes. Furthermore, while many other families of genes were altered, the gene families with the most genes altered included inflammation, cell cycle regulation, signal transduction, metabolism, and muscle contractile protein genes. This study is an early step toward identification of specific gene regulatory pathways that might lead to these differences, propagate disability, and increase vascular disease risk.

On the Relative Contribution of the Paretic Leg to the Control of Posture After Stroke

Background. Reduced postural steadiness and asymmetry of weight bearing are characteristic for posture after stroke. Objective. To examine the relative contribution of each leg to postural control in a cohort of 33 stroke patients at 5 stages during 3 months of inpatient rehabilitation, while taking clinical scores of sensory and motor impairments of the paretic leg into account. Methods. Participants were instructed to stand as symmetrically as possible under both sensory and cognitive manipulations, while a dual-plate force platform was used to assess the contribution of each leg to postural control, quantified by the amplitude, velocity, and regularity of recorded center-of-pressure trajectories. A greater contribution of the nonparetic leg was expected, particularly in patients with ankle clonus, disturbed sensibility, and lack of selective muscle control on the paretic side. Results. With follow-up assessments, weight-bearing asymmetry and postural steadiness improved. Patients strongly relied on visual information. When attention was distracted by having the patients perform an arithmetic task, weight-bearing asymmetry increased, suggesting that symmetric weight bearing was attention demanding. Patients with severe motor impairments of the paretic leg showed greater static (weight-bearing) and dynamic (lateralized control) asymmetries than patients with limited motor impairments, whereas postural steadiness did not differ between these subgroups. Disturbed sensation did not affect weight-bearing asymmetry, postural steadiness, or lateralized control. Conclusion. Patients with severe motor impairments of the paretic leg employ an effective compensatory strategy consisting of asymmetric weight bearing and lateralized control.

Nonuniform Weakness in the Paretic Knee and Compensatory Strength Gains in the Nonparetic Knee Occurs after Stroke

Background: This study was designed to quantify torque production at different joint angles in the paretic and nonparetic knee joints of individuals with stroke. Methods: Extension and flexion torques were measured at 6 angles of the knee joint and normalized to peak torque in 19 subjects with stroke and 19 controls. Results: Paretic knee extension torque was lower than controls when the knee was positioned near extension. In contrast, nonparetic knee extension and flexion torques were higher than controls when the knee was positioned near full flexion. Conclusions: The paretic knee extensors demonstrated exaggerated weakness at short muscle lengths and the nonparetic knee extensors and flexors demonstrated selective strength gains. Clinicians should therefore consider paretic knee extensor strengthening near full extension and promote symmetrical use of the legs to prevent compensatory overuse of the nonparetic leg.

Intrinsic muscle strength and voluntary activation of both lower limbs and functional performance after stroke

The objective of this study was to assess the nature of muscle weakness in both legs after stroke compared with able-bodied control individuals and to examine whether there is a relationship between the degree of muscle weakness and coactivation of knee extensors and flexors as well as voluntary activation capacity of knee extensors of both paretic and non-paretic legs and indices of functional performance. Maximal voluntary isometric torques of knee extensors (MVCe) and flexors (MVCf) were determined in 14 patients (bilaterally) and 12 able-bodied controls. Simultaneous measurements were made of torque and surface EMG from agonist and antagonist muscles. Coactivation was calculated. Supramaximal triplets were evoked with electrical stimulation to estimate maximal torque capacity and degree of voluntary activation of knee extensors. MVCs, activation and coactivation parameters were correlated to scores of seven functional performance tests. MVCe, MVCf and voluntary activation were lower in paretic lower limb (PL) compared with both non-paretic lower limb (NL) and control. Besides, all these parameters of NL were also lower than control. Electrically evoked torque capacity of knee extensors of PL was about 60% of both NL and control, which were not significantly different from each other. Strong significant correlations between strength, as well as voluntary activation, and functional performance were found. Coactivation did not correlate well with functional performance. Thus, whereas for NL activation failure can explain weakness, for PL both activation failure and reduced intrinsic torque capacity are responsible for the severe weakness. Activation capacity and muscle strength correlated strongly to functional performance, while coactivation did not.

Lower extremity passive range of motion in community-ambulating stroke survivors.

Physical therapists may prescribe stretching exercises for individuals with stroke to improve joint integrity and to reduce the risk of secondary musculoskeletal impairment. While deficits in passive range of motion (PROM) exist in stroke survivors with severe hemiparesis and spasticity, the extent to which impaired lower extremity PROM occurs in community-ambulating stroke survivors remains unclear. This study compared lower extremity PROM in able-bodied individuals and independent community-ambulatory stroke survivors with residual stroke-related neuromuscular impairments. Our hypothesis was that the stroke group would show decreased lower extremity PROM in the paretic but not the nonparetic side and that decreased PROM would be associated with increased muscle stiffness and decreased muscle length. Individuals with chronic poststroke hemiparesis who reported the ability to ambulate independently in the community (n = 17) and age-matched control subjects (n = 15) participated. PROM during slow (5 degrees/sec) hip extension, hip flexion, and ankle dorsiflexion was examined bilaterally using a dynamometer that measured joint position and torque. The maximum angular position of the joint (ANGmax), torque required to achieve ANGmax (Tmax), and mean joint stiffness (K) were measured. Comparisons were made between able-bodied and paretic and able-bodied and nonparetic limbs. Contrary to our expectations, between-group differences in ANGmax were observed only during hip extension in which ANGmax was greater bilaterally in people post-stroke compared to control subjects (P <or= 0.05; stroke = 13 degrees, able-bodied = -1 degree). Tmax, but not K, was also significantly higher during passive hip extension in paretic and nonparetic limbs compared to control limbs (P <or= 0.05; stroke = 40 Nm, able-bodied = 29 Nm). Compared to the control group, Tmax was increased during hip flexion in the paretic and nonparetic limbs of post-stroke subjects (P <or= 0.05, stroke = 25 Nm, able-bodied = 18 Nm). K in the nonparetic leg was also increased during hip flexion (P <or= 0.05, nonparetic = 0.52 Nm/degree, able-bodied = 0.37 Nm/degree.) This study demonstrates that community-ambulating stroke survivors with residual neuromuscular impairments do not have decreased lower extremity PROM caused by increased muscle stiffness or decreased muscle length. In fact, the population of stroke survivors examined here appears to have more hip extension PROM than age-matched able-bodied individuals. The clinical implications of these data are important and suggest that lower extremity PROM may not interfere with mobility in community-ambulating stroke survivors. Hence, physical therapists may choose to recommend activities other than stretching exercises for stroke survivors who are or will become independent community ambulators.

Effects of Prosthetic Gait Training for Stroke Patients to Induce Use of the Paretic Leg: A Report of Three Cases

During recovery from a stroke, body weight-bearing on a paretic leg is spontaneously avoided. In physiotherapy for hemiparetic gait, as long as the patients can use their non-paretic leg, adaptive and compensatory strategies are always used to support and move the body. We examined the effects of gait training using prosthetics to induce the use of a paretic leg during walking. The prosthesis was applied to the non-paretic leg of three right hemiparetic patients. Prosthetic gait training was performed until finishing 5 successive motor learning sessions involving walking over 200 m and the changes of asymmetric gait performances were analyzed. The ground reaction forces during the initial stance phase of the paretic leg were increased in all patients after prosthetic gait training. Simultaneously, the propulsive force produced by the paretic leg was increased in 2 patients. By contrast, another patient developed more use of his non-paretic leg for propulsion corresponding to acquiring stability on the paretic leg, resulting in an improvement in single-support-time asymmetry. Task-specific effects provided by prosthetic gait training may be able to reorganize the motor strategy for hemiparetic gait by inducing the use of the paretic leg to support and propell the body.

Relationship between walking function and 1-legged bicycling test in subjects in the later stage post-stroke

The aim of the present study was to examine the correlation between 1-legged bicycling and the 6-minute walk test (6MWT) in subjects post-stroke. A further aim was to analyse the relationship between specific stroke impairment and walking endurance. Thirty-four subjects (mean age 60 (standard deviation (SD) 4.1) years; mean time post-stroke 62 (SD 33) months) with stroke at least 6 months earlier were tested. Subjects were evaluated using the 6MWT (distance, heart rate, systolic blood pressure), 1-legged bicycling (VO2peak, maximal workload (Wmax), heart rate, systolic blood pressure, total exercise time), Fugl-Meyer motor function scale for the lower extremity and Berg Balance Scale. Correlational analyses were used to evaluate the relationships between variables. There was a low correlation between 6MWT and VO2peak (rs=0.39) and a moderate correlation with Wmax (rs=0.64) and total exercise time (rs=0.58) (p<0.001) during 1-legged bicycling test for the paretic leg. However, no significant correlation was found in the non-paretic leg. Motor function for the lower extremity and Berg Balance Scale showed a high (rs=0.72) and moderate (rs=0.68) correlation, respectively, with the 6MWT. The 6MWT is influenced by motor function and balance as well as cardiorespiratory fitness. Heart rate and systolic blood pressure indicate cardiovascular stress, but the 6MWT cannot be used alone to evaluate fitness in subjects with stroke in the later stages.

In vivo gastrocnemius muscle fascicle length in children with and without diplegic cerebral palsy

The effect of spastic cerebral palsy on in vivo gastrocnemius muscle fascicle length is not clear. Similarity of fascicle lengths in children with diplegia and typically developing children, but shortening of fascicle lengths in the paretic legs of children with hemiplegia compared with the non-paretic legs, are both reported. In the former case, comparisons were made between fascicle lengths normalized to leg length, whereas in the latter case, absolute fascicle lengths were compared. The inherent assumptions when normalizing fascicle length (measured via ultrasonography) were not validated, raising the possibility that inappropriate normalization contributed to the controversy. We used statistical methods to control the potential confounding effect of leg length on fascicle length, and tested the feasibility of the normalization method for a group of 18 children with diplegia (nine males, nine females; mean age 8y 7mo [SD 3y 11mo], range 2-15y; Gross Motor Function Classification System levels II and III) and 50 typically developing children (20 males, 30 females; mean age 9y 1mo [SD 2y 4mo], range 4-14y). Children with diplegia, as a group, had shorter absolute and normalized fascicle lengths (p<0.05) but we could not refute the appropriateness of the normalization method. Other methodological issues (such as sample characteristics) might have contributed to the apparent controversy between the studies.

Relationships Between Muscle Activity and Anteroposterior Ground Reaction Forces in Hemiparetic Walking

Turns LJ, Neptune RR, Kautz SA. Relationships between muscle activity and anteroposterior ground reaction forces in hemiparetic walking. Objective To determine relationships between muscle activity and propulsive impulse in hemiparetic walking. Design Cross-sectional. Setting Gait analysis laboratory. Participants Forty-nine poststroke patients with chronic hemiparesis, stratified into hemiparetic severity subgroups based on Brunnstrom stages of motor recovery, walking at their self-selected speed. Interventions Not applicable. Main Outcome Measures Percent of muscle activity in the paretic and nonparetic legs and net anteroposterior (AP) ground reaction force impulse (ie, the time integral of the AP ground reaction force) within 4 regions of the stance phase (first double support, first and second halves of single support, and second double support). Results Medial gastrocnemius and soleus muscle activity correlated positively with paretic propulsion in the second half of single support and double support across all subjects and subjects grouped by hemiparetic severity. Tibialis anterior correlated negatively with paretic propulsion during preswing across all subjects and for subjects with moderate and severe hemiparesis. Rectus femoris activity also correlated negatively with preswing propulsion for the severe group. Uniarticular knee extensor activity correlated only with increased paretic braking in the first double-support phase for the severe hemiparesis group. Nonparetic leg muscle activity correlated with propulsive impulses across all subjects, but not within the severe group exclusively. Conclusions Paretic propulsion is strongly associated with increased plantarflexor activity and also negatively associated with increased leg flexor activity, especially in the severe hemiparesis group. These results suggest that exaggerated flexor muscle activity may counteract the effects of the plantarflexors by offloading the leg and interfering with the limb’s ability to generate appropriate AP ground reaction forces. There is also evidence for specific relationships between paretic braking and nonparetic propulsive forces and changes in timing of muscle activation.

Differences in gastrocnemius muscle architecture between the paretic and non-paretic legs in children with hemiplegic cerebral palsy

The aim of this study was to investigate the architectural alterations of skeletal muscle following hemiplegic cerebral palsy. If associated with functional and clinical measures of disability, information on muscle architecture could then be used as an objective tool in the assessment of motor disability in these patients. Ultrasonography was used to assess in vivo the gastrocnemius muscle architecture in the paretic and non-paretic legs of eight children with cerebral palsy. Fascicle length and muscle thickness at the resting ankle position were reduced in the paretic compared to the non-paretic legs by up to 18% and 20%, respectively (P<0.05), indicating a loss of both in-series and in-parallel sarcomeres in the affected muscles. However, pennation angle was similar (P>0.05) in the two legs. The present results indicate that paresis in hemiplegic cerebral palsy may affect the geometry of skeletal muscle. Further studies are required to examine the relation between muscle architecture, severity of motor disability, and treatment.

Circuit Training in Community-Living “Younger” Men After Stroke

We sought to assess a training program focused on muscle strength and endurance in persons with prior stroke. Thirty men with a slight hemiparesis caused by a first occurrence of stroke at least 6 months earlier were included with an average age of 54 years. The following was assessed before and after an 8-week period: muscle strength, endurance, work capacity, and activity level. The training group consisted of 21 persons and 9 served as control subjects. There were no differences between the groups in the various assessments from the start. The training was set up as circuit training with 5 stations aiming to strengthen the muscles and increase endurance in the bilateral lower limbs. The session lasted for 45 minutes, 3 times per week, for 8 weeks. On eligible persons in the training group, double-sided muscle biopsies were also performed before and after. There was significance in improved muscle strength and improved peak oxygen uptake for the paretic leg, which was reflected in the muscle enzymes. The nonparetic side also showed improvement, but to a lesser extent. The control group remained unchanged. Stroke survivors can improve muscle strength, endurance, and work capacity in both the paretic and nonparetic leg with a circuit training program.

Recovery of Standing Balance and Health-Related Quality of Life After Mild or Moderately Severe Stroke

Garland SJ, Ivanova TD, Mochizuki G. Recovery of standing balance and health-related quality of life after mild or moderately severe stroke. Objective To examine the physiologic and functional recovery of standing balance and health-related quality of life (HRQOL) in people after mild and moderate stroke. Design Inception cohort study with evaluations at 1 month and 3 months poststroke. Setting Laboratory. Participants Twenty-nine volunteers who had sustained a stroke. Subjects were categorized into mild and moderate groups. Interventions Not applicable. Main Outcome Measures Functional balance was assessed (Clinical Outcome Variables Scale [COVS]) and physiologic measures (electromyography, postural sway) were taken when subjects stood quietly on a force platform and when they performed a rapid unilateral arm-raise perturbation. The Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) was administered to evaluate HRQOL. Results Subjects in the mild group were approaching maximal scores on the COVS (87.7±4.1/91) at 3 months poststroke, yet had significant impairment in paretic muscle activation patterns when compared with healthy subjects. Subjects in the moderate group had increased paretic muscle activation over the 2 months, accompanied by significant increases of 10.7±5.9 points on the COVS. For both groups, there was significantly less postural sway on the paretic than the nonparetic leg and significant improvements in the SF-36 (physical component) over time. Conclusions Subjects recovering from a stroke showed a significant improvement in physical HRQOL and functional and physiologic balance, yet the physiologic balance recovery was not complete even in the mild group.

Determinants of Walking Function After Stroke: Differences by Deficit Severity

Patterson SL, Forrester LW, Rodgers MM, Ryan AS, Ivey FM, Sorkin JD, Macko RF. Determinants of walking function after stroke: differences by deficit severity. Objectives To investigate the relationship of cardiovascular fitness (V o 2peak), neurologic deficits in balance and leg strength, and body composition to ambulatory function after stroke and to determine whether these relationships differ between those with milder versus more severe gait deficits. Design Cross-sectional correlation study. Setting Outpatient clinic of an academic medical center. Participants Seventy-four people (43 men, 31 women; mean age ± standard deviation, 64±10y) with chronic hemiparetic stroke. Interventions Not applicable. Main Outcome Measures Thirty-foot (9.1-m) walk velocity, 6-minute walk distance, V o 2peak, Berg Balance Scale score, bilateral quadriceps eccentric torque, total and regional lean mass, and percentage of fat mass. Results Short-distance walking correlated significantly with cardiovascular fitness, balance, paretic leg strength, nonparetic leg strength, percentage of body fat, and paretic lean mass but not with nonparetic lean mass. Long-distance walking correlated significantly with cardiovascular fitness, balance, paretic leg strength, nonparetic leg strength, and paretic lean mass but not with percentage of body fat or nonparetic lean mass. Stepwise regression showed that cardiovascular fitness, balance, and paretic leg strength were independently associated with long-distance walking ( r 2=.60, P<.001). Variance in long-distance walking was largely explained by balance for those who walked more slowly (<.48m/s) for short distances ( r 2=.42, P<.001) and by cardiovascular fitness for those who walked more quickly (>.48m/s) for short distances ( r 2=.26, P=.003). Conclusions Short-distance walking after stroke is related to balance, cardiovascular fitness, and paretic leg strength. Long-distance walking ability differs by gait deficit severity, with balance more important in those who walk more slowly and cardiovascular fitness playing a greater role in those who walk more quickly. Improved understanding of the factors that predict ambulatory function may assist the design of individualized rehabilitation strategies across the spectrum of gait deficit severity in those with hemiparetic stroke.

Relationship Between Step Length Asymmetry and Walking Performance in Subjects With Chronic Hemiparesis

Balasubramanian CK, Bowden MG, Neptune RR, Kautz SA. Relationship between step length asymmetry and walking performance in subjects with chronic hemiparesis. Objective To understand the relationship between step length asymmetry and hemiparetic walking performance. Design Descriptive. Setting Gait analysis laboratory. Participants Convenience sample of 49 subjects with chronic hemiparesis. Interventions Not applicable. Main Outcome Measures Subjects walked at their self-selected walking speed over both an instrumented mat and forceplates to collect spatiotemporal parameters and ground reaction forces, respectively. Step length asymmetry was quantified by using a step length ratio (SLR) defined as paretic step length divided by nonparetic step length. Paretic leg propulsion, self-selected walking speed, hemiparetic severity (assessed by Brunnstrom stages of motor recovery), and some spatiotemporal walking parameters quantified the hemiparetic walking performance. Paretic leg propulsion was quantified by the paretic propulsion (P P) ratio, calculated as the percentage contribution of paretic leg to the total propulsive impulse. Results Significant negative correlation ( r=−.78) was revealed between SLR and P P, indicating that subjects generating less propulsive force with the paretic leg walked asymmetrically with longer paretic steps than nonparetic steps. SLR and self-selected walking speed revealed a weaker correlation ( r=−.35), whereas hemiparetic severity correlated strongly with SLR (ρ=−.53). Conclusions Step length asymmetry is related to propulsive force generation during hemiparetic walking. Subjects generating least paretic propulsion walk with relatively longer paretic steps. This suggests that one of the mechanisms for the longer paretic step may be the relatively greater compensatory nonparetic leg propulsion. Further, those with more severe hemiparesis (those dependent on abnormal flexor and extensor synergies) walk with the longest paretic steps relative to nonparetic. Finally, our results indicated that asymmetrical step lengths may not necessarily limit the self-selected walking speed, likely due to other compensatory mechanisms.

RELATIONSHIP BETWEEN CLINICAL MEASURES OF PARETIC LOWER EXTREMITY MOTOR CONTROL AT 1 MONTH AND GAIT SPEED AT 6 MONTHS POST STROKE

Purpose/Hypothesis: Gait speed is a simple but highly reliable and responsive measure of walking disability that has been recommended as an outcome measure in stroke rehabilitation. Gait speed may depend critically on motor control of the paretic lower extremity (LE) during both stance and swing phases. The purposes of this project were to 1) determine relationships between simple clinical measures of paretic LE stance and swing phase control, tested at 1 month post stroke, and gait speed at 6 months post stroke and 2) compare month 1 measures of stance phase and swing phase control with respect to degree of association with walking outcome. Number of Subjects: Thirty-three subjects (18 men, 15 women; mean age = 58.7 ± 17.3 years) with a diagnosis of a single, unilateral stroke participated in the study. All subjects had significant LE motor impairment as indicated by a baseline Fugl-Meyer Lower Extremity Motor Scale (FM) score 28. Materials/Methods: Subjects were tested at monthly intervals from 1 to 6 months post stroke as part of a larger study. Measures of paretic LE motor control included the Step Test (ST), the Upright Motor Control test (UMCT), and the FM. The ST performed with the non-paretic leg stepping (ST-NP) and the extension component of the UMCT (UMCT-E) required paretic LE extensor muscle activation (stance control), while the ST performed with the paretic leg stepping (ST-P) and the flexion component of the UMCT (UMCT-F) required paretic LE flexor muscle activation (swing control). The FM required both extensor and flexor muscle control and also included reflexes and coordination. Gait speed was calculated from performance of the 10-m walk test at the subject's “usual, comfortable” pace. Statistical analyses included Pearson correlations with Bonferroni adjustment for multiple comparisons and stepwise regression analysis. Significance level was set at p <; .05. Results: With the exception of UMCT-E, all month 1 measures of paretic LE motor control were significantly associated with month 6 GS (r = .67–.85). Associations were somewhat stronger for measures of swing as compared to stance phase control. The association between month 1 ST-NP and ST-P scores was very strong (r = .91), whereas that between UMCT-E and UMCT-F scores was more moderate (r =.68). Younger age, higher ST-P scores, and higher FM scores at 1 month post stroke were associated with faster GS at 6 months post stroke (adjusted R2 = .74, p <;.001), with ST-P scores accounting for >; 70% of the variance. Conclusions: The degree of paretic LE motor control present at 1 month post stroke relates to gait speed at 6 months post stroke. Measures of both stance and swing phase control relate to walking outcome, with the ability to activate paretic LE flexors as needed for swing phase making a somewhat greater contribution. Clinical Relevance: An understanding of how early paretic LE motor control contributes to later walking outcome provides a basis for optimization of assessment and intervention strategies following mild to moderate stroke.