Pedaling alters the excitability and modulation of vastus medialis H-reflexes after stroke

Symmetry Is Associated With Interlimb Coordination During Walking and Pedaling After Stroke

BACKGROUND AND PURPOSE

Asymmetry during walking may be explained by impaired interlimb coordination. We examined these associations: (1) propulsive symmetry with interlimb coordination during walking, (2) work symmetry with interlimb coordination during pedaling, and (3) work symmetry and interlimb coordination with clinical impairment.

METHODS

Nineteen individuals with chronic stroke and 15 controls performed bilateral, lower limb pedaling with a conventional device and a device with a bisected crank and upstroke assistance. Individuals with stroke walked on a split-belt treadmill. Measures of symmetry (%Propulsionwalk, %Workped) and interlimb phase coordination index (PCIwalk, PCIped) were computed. Clinical evaluations were the lower extremity Fugl-Meyer (FMLE) and walking speed. Associations were assessed with Spearman's rank correlations.

RESULTS

Participants with stroke displayed asymmetry and impaired interlimb coordination compared with controls (P ≤ 0.001). There were significant correlations between asymmetry and impaired interlimb coordination (walking: R2 = 0.79, P < 0.001; pedaling: R2 = 0.62, P < 0.001) and between analogous measures across tasks (%Workped, %Propulsionwalk: R2 = 0.41, P = 0.01; PCIped, PCIwalk: R2 = 0.52, P = 0.003). Regardless of task, asymmetry and interlimb coordination were correlated with FMLE (R2 ≥ 0.48, P ≤ 0.004) but not walking speed. There was larger within group variation for %Propulsionwalk than %Workped (Z = 2.6, P = 0.005) and for PCIped than PCIwalk (Z = 3.6, P = 0.003).

DISCUSSION AND CONCLUSIONS

Pedaling may provide useful insights about walking, and impaired interlimb coordination may contribute to asymmetry in walking. Pedaling and walking provide distinct insights into stroke-related impairments, related to whether the task allows compensation (walking > pedaling) or compels paretic limb use (pedaling > walking). Pedaling a device with a bisected crank shaft may have therapeutic value.Video Abstract available for more insight from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A365).

Pedaling improves gait ability of hemiparetic patients with stiff-knee gait: fall prevention during gait

BACKGROUND AND PURPOSE

Stiff-knee gait, which is a gait abnormality observed after stroke, is characterized by decreased knee flexion angles during the swing phase, and it contributes to a decline in gait ability. This study aimed to identify the immediate effects of pedaling exercises on stiff-knee gait from a kinesiophysiological perspective.

METHODS

Twenty-one patients with chronic post-stroke hemiparesis and stiff-knee gait were randomly assigned to a pedaling group and a walking group. An ergometer was set at a load of 5 Nm and rotation speed of 40 rpm, and gait was performed at a comfortable speed; both the groups performed the intervention for 10 min. Kinematic and electromyographical data while walking on flat surfaces were immediately measured before and after the intervention.

RESULTS

In the pedaling group, activity of the rectus femoris significantly decreased from the pre-swing phase to the early swing phase during gait after the intervention. Flexion angles and flexion angular velocities of the knee and hip joints significantly increased during the same period. The pedaling group showed increased step length on the paralyzed side and gait velocity.

CONCLUSIONS

Pedaling increases knee flexion during the swing phase in hemiparetic patients with stiff-knee gait and improves gait ability.

Impaired interlimb coordination is related to asymmetries during pedaling after stroke

OBJECTIVE

To understand whether lower limb asymmetry in chronic stroke is related to paretic motor impairment or impaired interlimb coordination.

METHODS

Stroke and control participants performed conventional, unilateral, and bilateral uncoupled pedaling. During uncoupled pedaling, the pedals were mechanically disconnected. Paretic mechanical work was measured during conventional pedaling. Pedaling velocity and muscle activity were compared across conditions and groups. Relative limb phasing was examined during uncoupled pedaling.

RESULTS

During conventional pedaling, EMG and mechanical work were lower in the paretic than the non-paretic limb (asymmetry). During unilateral pedaling with the paretic limb, muscle activity was larger, but velocity was slower and more variable than during conventional pedaling (evidence of paretic motor impairment). During uncoupled pedaling, muscle activity increased further, but velocity was slower and more variable than in other conditions (evidence of impaired interlimb coordination). Relative limb phasing was impaired in stroke participants. Regression analysis suggested that interlimb coordination may be a stronger predictor of asymmetry than paretic motor impairment.

CONCLUSIONS

Paretic motor impairment and impaired interlimb coordination may contribute to asymmetry during pedaling after stroke.

SIGNIFICANCE

Rehabilitation that addresses paretic motor impairment and impaired interlimb coordination may improve symmetry and maximize improvement.

Recumbent cycling with integrated volitional control electrical stimulation improves gait speed during the recovery stage in stroke patients

The purpose of this study was to investigate the effect of recumbent cycling with integrated volitional control electrical stimulation (IVES) on gait ability in stroke patients. Six stroke patients (all male; average age, 55.7±8.3 years) participated. Recumbent cycling (R-cycling) was performed with and without IVES in the power assist (IVES-P) mode. The targeted muscle for electrostimulation was the tibialis anterior. Patients performed 10 min of IVES-P mode plus R-cycling (program A) or R-cycling alone (program B), once per day, 5 times per week. Patients completed two sets of each program, alternating between programs each week. Gait speed and the number of steps numbers on a 10-m walking test was assessed before and after each interventional session. Program A improved gait speed, but not the number of steps, to a greater extent than that in program B. Specifically, the combined intervention significantly improved gait speed in the first set, but not the second set of the intervention. R-cycling with IVES-P mode improved gait speed during the recovery stage in stroke patients to a greater extent than that achieved with R-cycling alone. Thus, this combined therapy has potential as a standardized treatment in the field of rehabilitation medicine.

Brain Activation During Passive and Volitional Pedaling After Stroke

Background:

Prior work indicates that pedaling-related brain activation is lower in people with stroke than in controls. We asked whether this observation could be explained by between-group differences in volitional motor commands and pedaling performance.

Methods:

Individuals with and without stroke performed passive and volitional pedaling while brain activation was recorded with functional magnetic resonance imaging. The passive condition eliminated motor commands to pedal and minimized between-group differences in pedaling performance. Volume, intensity, and laterality of brain activation were compared across conditions and groups.

Results:

There were no significant effects of condition and no Group × Condition interactions for any measure of brain activation. Only 53% of subjects could minimize muscle activity for passive pedaling.

Conclusions:

Altered motor commands and pedaling performance are unlikely to account for reduced pedaling-related brain activation poststroke. Instead, this phenomenon may be due to functional or structural brain changes. Passive pedaling can be difficult to achieve and may require inhibition of excitatory descending drive.

Physical Exercise as a Diagnostic, Rehabilitation, and Preventive Tool: Influence on Neuroplasticity and Motor Recovery after Stroke

Stroke remains a leading cause of adult motor disabilities in the world and accounts for the greatest number of hospitalizations for neurological disease. Stroke treatments/therapies need to promote neuroplasticity to improve motor function. Physical exercise is considered as a major candidate for ultimately promoting neural plasticity and could be used for different purposes in human and animal experiments. First, acute exercise could be used as a diagnostic tool to understand new neural mechanisms underlying stroke physiopathology. Indeed, better knowledge of stroke mechanisms that affect movements is crucial for enhancing treatment/rehabilitation effectiveness. Secondly, it is well established that physical exercise training is advised as an effective rehabilitation tool. Indeed, it reduces inflammatory processes and apoptotic marker expression, promotes brain angiogenesis and expression of some growth factors, and improves the activation of affected muscles during exercise. Nevertheless, exercise training might also aggravate sensorimotor deficits and brain injury depending on the chosen exercise parameters. For the last few years, physical training has been combined with pharmacological treatments to accentuate and/or accelerate beneficial neural and motor effects. Finally, physical exercise might also be considered as a major nonpharmacological preventive strategy that provides neuroprotective effects reducing adverse effects of brain ischemia. Therefore, prestroke regular physical activity may also decrease the motor outcome severity of stroke.

A novel fMRI paradigm suggests that pedaling-related brain activation is altered after stroke

The purpose of this study was to examine the feasibility of using functional magnetic resonance imaging (fMRI) to measure pedaling-related brain activation in individuals with stroke and age-matched controls. We also sought to identify stroke-related changes in brain activation associated with pedaling. Fourteen stroke and 12 control subjects were asked to pedal a custom, MRI-compatible device during fMRI. Subjects also performed lower limb tapping to localize brain regions involved in lower limb movement. All stroke and control subjects were able to pedal while positioned for fMRI. Two control subjects were withdrawn due to claustrophobia, and one control data set was excluded from analysis due to an incidental finding. In the stroke group, one subject was unable to enter the gantry due to excess adiposity, and one stroke data set was excluded from analysis due to excessive head motion. Consequently, 81% of subjects (12/14 stroke, 9/12 control) completed all procedures and provided valid pedaling-related fMRI data. In these subjects, head motion was ≤3 mm. In both groups, brain activation localized to the medial aspect of M1, S1, and Brodmann's area 6 (BA6) and to the cerebellum (vermis, lobules IV, V, VIII). The location of brain activation was consistent with leg areas. Pedaling-related brain activation was apparent on both sides of the brain, with values for laterality index (LI) of -0.06 (0.20) in the stroke cortex, 0.05 (±0.06) in the control cortex, 0.29 (0.33) in the stroke cerebellum, and 0.04 (0.15) in the control cerebellum. In the stroke group, activation in the cerebellum - but not cortex - was significantly lateralized toward the damaged side of the brain (p = 0.01). The volume of pedaling-related brain activation was smaller in stroke as compared to control subjects. Differences reached statistical significance when all active regions were examined together [p = 0.03; 27,694 (9,608) μL stroke; 37,819 (9,169) μL control]. When individual regions were examined separately, reduced brain activation volume reached statistical significance in BA6 [p = 0.04; 4,350 (2,347) μL stroke; 6,938 (3,134) μL control] and cerebellum [p = 0.001; 4,591 (1,757) μL stroke; 8,381 (2,835) μL control]. Regardless of whether activated regions were examined together or separately, there were no significant between-group differences in brain activation intensity [p = 0.17; 1.30 (0.25)% stroke; 1.16 (0.20)% control]. Reduced volume in the stroke group was not observed during lower limb tapping and could not be fully attributed to differences in head motion or movement rate. There was a tendency for pedaling-related brain activation volume to increase with increasing work performed by the paretic limb during pedaling (p = 0.08, r = 0.525). Hence, the results of this study provide two original and important contributions. First, we demonstrated that pedaling can be used with fMRI to examine brain activation associated with lower limb movement in people with stroke. Unlike previous lower limb movements examined with fMRI, pedaling involves continuous, reciprocal, multijoint movement of both limbs. In this respect, pedaling has many characteristics of functional lower limb movements, such as walking. Thus, the importance of our contribution lies in the establishment of a novel paradigm that can be used to understand how the brain adapts to stroke to produce functional lower limb movements. Second, preliminary observations suggest that brain activation volume is reduced during pedaling post-stroke. Reduced brain activation volume may be due to anatomic, physiology, and/or behavioral differences between groups, but methodological issues cannot be excluded. Importantly, brain action volume post-stroke was both task-dependent and mutable, which suggests that it could be modified through rehabilitation. Future work will explore these possibilities.

Impaired foot-force direction regulation during postural loaded locomotion in individuals poststroke

Following stroke, hemiparesis results in impaired motor control. Specifically, inappropriate direction of foot-forces during locomotion has been reported. In our previous study (Liang and Brown 2011) that examined poststroke foot-force direction during a seated, supported locomotor task, we observed that foot-force control capabilities were preserved poststroke. In this current study, we sought to better understand the mechanisms underlying the interaction of locomotor and postural control as an interactive mechanism that might interfere, poststroke, with appropriate foot-force generation. We designed an experiment in which participants performed biomechanically controlled locomotor tasks, under posturally challenged pedaling conditions while they generated mechanical output that was comparable to pedaling conditions without postural challenge, thus allowing us to monitor the strategies that the nervous system adopts when postural conditions were manipulated. We hypothesized that, with postural influence, individuals poststroke would generate inappropriate shear forces accompanied by inappropriate changes to muscle activity patterns when performing a mechanically controlled locomotor task, and would be exaggerated with increased postural loading. Sixteen individuals with chronic poststroke hemiparesis and 14 age-similar nonimpaired controls pedaled on a cycle ergometer under 1) seated supported and 2) nonseated postural loaded pedaling conditions, generating matched pedal force outputs of two effort levels. When we compared postural influence with seated pedaling, we observed increased magnitudes of forward-directed shear forces in the paretic legs associated with increased magnitude of leg extensor muscle activity, but not in controls. These findings provide evidence to support a model that describes independent controllers for posture and locomotion, but that the interaction between the two controllers is impaired poststroke.