T. George Hornby

Observation of Amounts of Movement Practice Provided During Stroke Rehabilitation

UNLABELLEDnLang CE, MacDonald JR, Reisman DS, Boyd L, Jacobson Kimberley T, Schindler-Ivens SM, Hornby TG, Ross SA, Scheets PL. Observation of amounts of movement practice provided during stroke rehabilitation.nnnOBJECTIVEnTo investigate how much movement practice occurred during stroke rehabilitation, and what factors might influence doses of practice provided.nnnDESIGNnObservational survey of stroke therapy sessions.nnnSETTINGnSeven inpatient and outpatient rehabilitation sites.nnnPARTICIPANTSnWe observed a convenience sample of 312 physical and occupational therapy sessions for people with stroke.nnnINTERVENTIONSnNot applicable.nnnMAIN OUTCOME MEASURESnWe recorded numbers of repetitions in specific movement categories and data on potential modifying factors (patient age, side affected, time since stroke, FIM item scores, years of therapist experience). Descriptive statistics were used to characterize amounts of practice. Correlation and regression analyses were used to determine whether potential factors were related to the amount of practice in the 2 important categories of upper extremity functional movements and gait steps.nnnRESULTSnPractice of task-specific, functional upper extremity movements occurred in 51% of the sessions that addressed upper limb rehabilitation, and the average number of repetitions/session was 32 (95% confidence interval [CI]=20-44). Practice of gait occurred in 84% of sessions that addressed lower limb rehabilitation and the average number of gait steps/session was 357 (95% CI=296-418). None of the potential factors listed accounted for significant variance in the amount of practice in either of these 2 categories.nnnCONCLUSIONSnThe amount of practice provided during poststroke rehabilitation is small compared with animal models. It is possible that current doses of task-specific practice during rehabilitation are not adequate to drive the neural reorganization needed to promote function poststroke optimally.

Metabolic Costs and Muscle Activity Patterns During Robotic- and Therapist-Assisted Treadmill Walking in Individuals With Incomplete Spinal Cord Injury

Background and Purpose. Robotic devices that provide passive guidance and stabilization of the legs and trunk during treadmill stepping may increase the delivery of locomotor training to subjects with neurological injury. Lower-extremity guidance also may reduce voluntary muscle activity as compared with compliant assistance provided by therapists. The purpose of this study was to investigate differences in metabolic costs and lower-limb muscle activity patterns during robotic- and therapist-assisted treadmill walking. Subjects. Twelve ambulatory subjects with motor incomplete spinal cord injury participated. Methods. In 2 separate protocols, metabolic and electromyographic (EMG) data were collected during standing and stepping on a treadmill with therapist and robotic assistance. During robotic-assisted walking, subjects were asked to match the kinematic trajectories of the device and maximize their effort. During therapist-assisted walking, subjects walked on the treadmill with manual assistance provided as necessary. Results. Metabolic costs and swing-phase hip flexor EMG activity were significantly lower when subjects were asked to match the robotic device trajectories than with therapist-assisted walking. These differences were reduced when subjects were asked to maximize their effort during robotic-assisted stepping, although swing-phase plantar-flexor EMG activity was increased. In addition, during standing prior to therapist- or robotic-assisted stepping, metabolic costs were higher without stabilization from the robotic device. Discussion and Conclusion. Differences in metabolic costs and muscle activity patterns between therapist- and robotic-assisted standing and stepping illustrate the importance of minimizing passive guidance and stabilization provided during step training protocols.

Allowing Intralimb Kinematic Variability During Locomotor Training Poststroke Improves Kinematic Consistency: A Subgroup Analysis From a Randomized Clinical Trial

Background: Locomotor training (LT) to improve walking ability in people poststroke can be accomplished with therapist assistance as needed to promote continuous stepping. Various robotic devices also have been developed that can guide the lower limbs through a kinematically consistent gait pattern. It is unclear whether LT with either therapist or robotic assistance could improve kinematic coordination patterns during walking. Objective: The purpose of this study was to determine whether LT with physical assistance as needed was superior to guided, symmetrical, robotic-assisted LT for improving kinematic coordination during walking poststroke. Design: This study was a randomized clinical trial. Methods: Nineteen people with chronic stroke (>6 months’ duration) participating in a larger randomized control trial comparing therapist- versus robotic-assisted LT were recruited. Prior to and following 4 weeks of LT, gait analysis was performed at each participants self-selected speed during overground walking. Kinematic coordination was defined as the consistency of intralimb hip and knee angular trajectories over repeated gait cycles and was compared before and after treatment for each group. Results: Locomotor training with therapist assistance resulted in significant improvements in the consistency of intralimb movements of the impaired limb. Providing consistent kinematic assistance during robotic-assisted LT did not result in improvements in intralimb consistency. Only minimal changes in discrete kinematics were observed in either group. Limitations: The limitations included a relatively small sample size and a lack of quantification regarding the extent of movement consistency during training sessions for both groups. Conclusions: Coordination of intralimb kinematics appears to improve in response to LT with therapist assistance as needed. Fixed assistance, as provided by this form of robotic guidance during LT, however, did not alter intralimb coordination.

Extrinsic flexor muscles generate concurrent flexion of all three finger joints

The role of the forearm (extrinsic) finger flexor muscles in initiating rotation of the metacarpophalangeal (MCP) joint and in coordinating flexion at the MCP, the proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints remains a matter of some debate. To address the biomechanical feasibility of the extrinsic flexors performing these actions, a computer simulation of the index finger was created. The model consisted of a planar open-link chain comprised of three revolute joints and four links, driven by the change in length of the flexor muscles. Passive joint characteristics, included in the model, were obtained from system identification experiments involving the application of angular perturbations to the joint of interest. Simulation results reveal that in the absence of passive joint torque, shortening of the extrinsic flexors results in PIP flexion (80 degrees ), but DIP (8 degrees ) and MCP (7 degrees ) joint extension. The inclusion of normal physiological levels of passive joint torque, however, results in simultaneous flexion of all three joints (63 degrees for DIP, 75 degrees for PIP, and 43 degrees for MCP). Applicability of the simulation results was confirmed by recording finger motion produced by electrical stimulation of the extrinsic flexor muscles for the index finger. These findings support the view that the extrinsic flexor muscles can initiate MCP flexion, and produce simultaneous motion at the MCP, PIP, and DIP joints.

Stimulation-induced changes in lower limb corticomotor excitability during treadmill walking in humans

Magnetic stimulation of human primary motor cortex (M1) paired with electrical stimulation of a peripheral motor nerve has been used to produce a lasting modulation of corticomotor (CM) excitability. This ‘paired associative stimulation’ (PAS) protocol has been used to induce bidirectional changes in excitability in upper limb CM pathways. The present study tested the hypothesis that temporally dependent PAS applied to the common peroneal nerve during the swing phase of walking would induce bidirectional changes in CM excitability consistent with the Hebbian principle of activity‐dependent plasticity. Fourteen subjects with no known neurological disorder participated in two data collection sessions each. PAS was delivered as a single block of 120 pairs of stimuli delivered in a 10 min period during treadmill walking at 4.0 km h−1. Changes in CM excitability were assessed by examining the size of motor potentials evoked by transcranial magnetic stimulation prior to and following PAS. Tibialis anterior motor‐evoked potentials amplitude increased to 121% over baseline when the magnetic stimulus was delivered over M1 after the estimated arrival time of the afferent volley in sensorimotor cortex and decreased to 83% of baseline when the magnetic stimulus was delivered prior to the estimated afferent volley arrival. This extent of modulation was undiminished following a further 10 min period of walking without stimulation. The temporal nature of the bidirectional effects following PAS, their rapid evolution and subsequent persistence supported the studys hypothesis and were similar to the effects described by others in quiescent muscles of the upper limb.

Heightened Flexor Withdrawal Responses in Subjects With Knee Osteoarthritis

UNLABELLEDnPatients with osteoarthritic (OA) knee pain often present with impaired muscle activation and function that may be attributed in part to hyperexcitability of flexion withdrawal reflexes (FWRs). The aim of this study was to investigate alterations in the excitability of FWR in individuals with knee OA and its potential associations with impaired quadriceps activation (QA) and subjective reports of pain. Twenty subjects with and 20 without knee OA (age, 45 to 75 years) participated. Impaired QA was determined in OA subjects during maximal volitional contraction of the quadriceps. FWRs were tested in isometric conditions using electrocutaneous stimulation applied at the medial foot at 1x and 2x FWR threshold and surface electromyographic recordings obtained from tibialis anterior (TA) and biceps femoris (BF). Joint torques at the hip, knee, and ankle were calculated and normalized to body mass. FWR threshold was significantly diminished in OA versus the control group (P < .01). In addition, FWR latencies were consistent with spinally mediated responses, with significantly earlier responses in OA versus control subjects of TA at threshold (P = .002) and BF at suprathreshold stimulation (P = .0006). Impaired QA was found in 4 of 20 OA subjects but was not correlated to FWR threshold or pain levels. Peak joint torques were diminished in the OA versus the control group (P < .0006).nnnPERSPECTIVEnIncreased excitability of FWRs was evident in subjects with chronic knee osteoarthritis, including those subjects without resting pain, but was not associated with impaired QA. Management strategies for this patient population must consider altered pain processing in addition to addressing impairments found at the knee.

Heightened Flexor Withdrawal Response in Individuals With Knee Osteoarthritis Is Modulated by Joint Compression and Joint Mobilization

UNLABELLEDnPatients with chronic pain often present with hyperalgesia, possibly due to hyperexcitability of nociceptive pathways. The aim of the present study was to investigate alterations in flexor withdrawal reflex (FWR) excitability in individuals with knee osteoarthritis (OA) and the potential effect of specific physical inputs or therapeutic interventions (ie, joint compression and mobilization) on these behaviors. Ten subjects with and 10 without knee OA (age 45-75) were recruited. The FWR was examined utilizing suprathreshold, noxious electrocutaneous stimuli applied at the medial foot. Surface electromyographic (EMG) was recorded from the tibialis anterior (TA) and biceps femoris (BF), and peak joint torques recorded at the hip, knee, and ankle. FWR threshold was ascertained and responses at 2x threshold recorded after the following conditions: a maximal, volitional, joint-compression task, a sham hands-on intervention, and a Grade III oscillatory joint-mobilization intervention. A decreased threshold-to-flexor withdrawal response was found in the OA vs control group (P < .01). EMG and joint-torque FWR responses were further augmented in the OA group following the maximal joint-compression task (P < .05), yet remained unchanged or diminished in controls. Joint mobilization, but not sham intervention, reduced reflex responses significantly, although primarily by decreasing BF activity and knee torques (P < .05).nnnPERSPECTIVEnApplication of specific physical inputs to individuals with knee OA similar to those encountered during activity of daily living or during therapeutic interventions appear to modulate involuntary, nociceptive reflex responses. Routine weight-bearing activities such as walking may potentially enhance heightened FWR responses, while joint mobilization, a commonly used clinical intervention, may diminish reflex excitability.

Rapid and Long-term Adaptations in Gait Symmetry Following Unilateral Step Training in People With Hemiparesis

Background and Objective: Evidence for specific physical interventions that improve walking symmetry in individuals with hemiparesis poststroke is limited. The aim of this study was to investigate the rapid and prolonged effects of unilateral step training (UST) on step length asymmetry (SLA) in people with hemiparesis. Subjects and Design: Eighteen individuals with chronic hemiparesis and substantial SLA during overground walking participated in a single-group, pretest-posttest study. The study consisted of 2 phases, with 10 subjects participating in each phase; 2 subjects participated in both phases. Interventions and Measurements: To investigate rapid effects of UST, the participants completed a 20-minute session of UST on a treadmill with their unimpaired limb, with the impaired limb held stationary off the treadmill. Data for spatiotemporal gait parameters during overground walking at self-selected and fastest speeds were collected prior to and following UST, with follow-up measurements at 1 day and 1 week. To investigate the prolonged effects, the participants completed ten 20-minute sessions of UST. Data for spatiotemporal gait parameters were collected prior to training as well as after every third session, with follow-up measurements at 1 and 2 weeks. Results: Immediately following UST, SLA tested during fast-paced overground walking improved by up to 13% (49% reduced to a 36% SLA), with changes retained for up to 24 hours. Following 10 sessions of UST, SLA improved significantly, with changes retained for up to 2 weeks. Limitations: Despite repeated baseline measurements, the absence of a control group was a limitation. Furthermore, stepping characteristics during UST were not quantified. Conclusion: Unilateral step training may improve spatiotemporal patterns in people with substantial gait asymmetry poststroke. Repeated training may be necessary for maintenance of adaptations.

Feasibility of high-repetition, task-specific training for individuals with upper-extremity paresis.

OBJECTIVE. We investigated the feasibility of delivering an individualized, progressive, high-repetition upper-extremity (UE) task-specific training protocol for people with stroke in the inpatient rehabilitation setting. METHOD. Fifteen patients with UE paresis participated in this study. Task-specific UE training was scheduled for 60 min/day, 4 days/wk, during occupational therapy for the duration of a participants inpatient stay. During each session, participants were challenged to complete ≥300 repetitions of various tasks. RESULTS. Participants averaged 289 repetitions/session, spending 47 of 60 min in active training. Participants improved on impairment and activity level outcome measures. CONCLUSION. People with stroke in an inpatient setting can achieve hundreds of repetitions of task-specific training in 1-hr sessions. As expected, all participants improved on functional outcome measures. Future studies are needed to determine whether this high-repetition training program results in better outcomes than current UE interventions.

Feasibility and Potential Efficacy of High-Intensity Stepping Training in Variable Contexts in Subacute and Chronic Stroke

Background. Previous data suggest that the amount and aerobic intensity of stepping training may improve walking poststroke. Recent animal and human studies suggest that training in challenging and variable contexts can also improve locomotor function. Such practice may elicit substantial stepping errors, although alterations in locomotor strategies to correct these errors could lead to improved walking ability. Objective. This unblinded pilot study was designed to evaluate the feasibility and preliminary efficacy of providing stepping practice in variable, challenging contexts (tasks and environments) at high aerobic intensities in participants >6 months and 1-6 months post-stroke. Methods. A total of 25 participants (gait speeds <0.9 m/s with no more than moderate assistance) participated in ≤40 training sessions (duration of 1 hour) within 10 weeks. Stepping training in variable, challenging contexts was performed at 70% to 80% heart rate reserve, with feasibility measures of total steps/session, ability to achieve targeted intensities, patient tolerance, dropouts, and adverse events. Gait speed, symmetry, and 6-minute walk were measured every 4 to 5 weeks or 20 sessions, with a 3-month follow-up (F/U). Results. In all, 22 participants completed ≥4 training weeks, averaging 2887 ± 780 steps/session over 36 ± 5.8 sessions. Self-selected (0.38 ± 0.27 to 0.66 ± 0.35 m/s) and fastest speed (0.51 ± 0.40 to 0.99 ± 0.58 m/s), paretic single-limb stance (20% ± 5.9% to 25% ± 6.4%), and 6-minute walk (141 ± 99 to 260 ± 146 m) improved significantly at posttraining. Conclusions. This preliminary study suggests that stepping training at high aerobic intensities in variable contexts was tolerated by participants poststroke, with significant locomotor improvements. Future studies should delineate the relative contributions of amount, intensity, and variability of stepping training to maximize outcomes.