A physiological basis for the development of rehabilitative strategies for spinally injured patients

Exploring How the Arms Can Help the Legs in Facilitating Gait Rehabilitation

Inspired by the ideas from the fields of gait rehabilitation, neuroscience, and locomotion biomechanics and energetics, a body of work is reviewed that has led to propose a conceptual framework for novel "self-assistive" walking devices that could further promote walking recovery from incomplete spinal cord injuries. The underlying rationale is based on a neural coupling mechanism that governs the coordinated movements of the arms and legs during walking, and that the excitability of these neural pathways can be exploited by actively engaging the arms during locomotor training. Self-assistive treadmill walking rehabilitation devices are envisioned as an approach that would allow an individual to actively use their arms to help the legs during walking. It is hoped that the conceptual framework inspires the design and use of self-assistive walking devices that are tailored to assist individuals with an incomplete spinal cord injury to regain their functional walking ability.

Spinal shock in severe SCI dogs and early implementation of intensive neurorehabilitation programs

Spinal shock is complex, paradoxical with sudden presentation, possibly leading to a guarded prognosis. Thus, it is suggested the need for early implementation of intensive neurorehabilitation. This prospective controlled blinded cohort study aims to understand the implication of spinal shock in neurorehabilitation of severe SCI dogs and the importance of its evaluation thought a spinal shock scale (SSS). 371 dogs were randomized by stratification according the presence of spinal shock in the SG (n = 245) or CG (n = 126). The SSS, a punctuation scale (0-7), was evaluated at admission and each 6 h for 3 days, each day for 15 days, each week for 6 weeks, each month until 3 months, followed by 3 monthly follow-ups. All dogs had similar land and underwater treadmill training with functional electrical stimulation. Observational dataset allowed an approximate level of power (1-β) of 0.90 and an α (Type I error) of 0.01, with a total of 11,088 SSS observations between two blinded observers and 18% of disagreement. 75% of the dogs were admitted in 24-48 h after injury, allowing early detection of spinal shock, and dogs admitted at 72 h with SSS ≥ 4 were not able to achieve ambulation. Regarding ambulation rate, there was a significant difference between groups, with 66.9% of ambulation in the SG and 97.6% in the CG. Also, there was a difference in regard to time until ambulation, with a mean of 31.57 days for the SG and 23.02 for the CG. The SSS estimated marginal means had an exponential decrease within the first 6 h, followed by a slower decrease, but always faster in spinal shock dogs diagnosed with non-compressive myelopathies. Thus, early intensive neurorehabilitation in dogs after severe SCI may benefit from SSS classifications at admission and during treatment to establish different therapeutic protocols according to each patient's needs, especially in deep pain negative dogs.

Spinal Locomotion in Cats Following Spinal Cord Injury: A Prospective Study

Simple Summary

Functional neurorehabilitation promotes neural reorganization by stimulating subjects without deep pain perception, leading to a faster recovery when compared to spontaneous recovery, and achieving fewer compensatory errors, or even deviations to neuropathic or adaptive pain pathways, such as spasticity. The present study demonstrates the importance of intensive and repetition-based functional neurorehabilitation, which is essential for subjects classified as grade 0 according to the modified Frankel scale.

Abstract

This article aimed to evaluate the safety and efficacy of intensive neurorehabilitation in paraplegic cats, with no deep pain perception (grade 0 on the modified Frankel scale), with more than three months of injury. Nine cats, admitted to the Arrábida Veterinary Hospital/Arrábida Animal Rehabilitation Center (CRAA), were subjected to a 12-week intensive functional neurorehabilitation protocol, based on ground and underwater treadmill locomotor training, electrostimulation, and kinesiotherapy exercises, aiming to obtain a faster recovery to ambulation and a modulated locomotor pattern of flexion/extension. Of the nine cats that were admitted in this study, 56% (n = 5) recovered from ambulation, 44% of which (4/9) did so through functional spinal locomotion by reflexes, while one achieved this through the recovery of deep pain perception. These results suggest that intensive neurorehabilitation can play an important role in ambulation recovery, allowing for a better quality of life and well-being, which may lead to a reduction in the number of euthanasia procedures performed on paraplegic animals.

Using a simple rope-pulley system that mechanically couples the arms, legs, and treadmill reduces the metabolic cost of walking

BACKGROUND

Emphasizing the active use of the arms and coordinating them with the stepping motion of the legs may promote walking recovery in patients with impaired lower limb function. Yet, most approaches use seated devices to allow coupled arm and leg movements. To provide an option during treadmill walking, we designed a rope-pulley system that physically links the arms and legs. This arm-leg pulley system was grounded to the floor and made of commercially available slotted square tubing, solid strut channels, and low-friction pulleys that allowed us to use a rope to connect the subject's wrist to the ipsilateral foot. This set-up was based on our idea that during walking the arm could generate an assistive force during arm swing retraction and, therefore, aid in leg swing.

METHODS

To test this idea, we compared the mechanical, muscular, and metabolic effects between normal walking and walking with the arm-leg pulley system. We measured rope and ground reaction forces, electromyographic signals of key arm and leg muscles, and rates of metabolic energy consumption while healthy, young subjects walked at 1.25 m/s on a dual-belt instrumented treadmill (n = 8).

RESULTS

With our arm-leg pulley system, we found that an assistive force could be generated, reaching peak values of 7% body weight on average. Contrary to our expectation, the force mainly coincided with the propulsive phase of walking and not leg swing. Our findings suggest that subjects actively used their arms to harness the energy from the moving treadmill belt, which helped to propel the whole body via the arm-leg rope linkage. This effectively decreased the muscular and mechanical demands placed on the legs, reducing the propulsive impulse by 43% (p < 0.001), which led to a 17% net reduction in the metabolic power required for walking (p = 0.001).

CONCLUSIONS

These findings provide the biomechanical and energetic basis for how we might reimagine the use of the arms in gait rehabilitation, opening the opportunity to explore if such a method could help patients regain their walking ability.

TRIAL REGISTRATION

 Study registered on 09/29/2018 in ClinicalTrials.gov (ID-NCT03689647).

Effect of Different Forms of Activity-Based Recovery Training on Bladder, Bowel, and Sexual Function After Spinal Cord Injury

OBJECTIVES

To investigate whether the urogenital and bowel functional gains previously demonstrated post-locomotor step training after chronic spinal cord injury could have been derived due to weight-bearing alone or from exercise in general.

DESIGN

Prospective cohort study; pilot trial with small sample size.

SETTING

Urogenital and bowel scientific core facility at a rehabilitation institute and spinal cord injury research center in the United States.

PARTICIPANTS

Men and women (N=22) with spinal cord injury (American Spinal Injury Association Impairment Scale grades of A-D) participated in this study.

INTERVENTIONS

Approximately 80 daily 1-hour sessions of either stand training or nonweight-bearing arm crank ergometry. Comparisons were made with previously published locomotor training data (step; N=7).

MAIN OUTCOME MEASURES

Assessments at both pre- and post-training timepoints included cystometry for bladder function and International Data Set Questionnaires for bowel and sexual functions.

RESULTS

Cystometry measurements revealed a significant decrease in bladder pressure and limited improvement in compliance with nonweight-bearing exercise but not with standing. Although International Data Set questionnaires revealed profound bowel dysfunction and marked deficits in sexual function pretraining, no differences were identified poststand or after nonweight-bearing exercise.

CONCLUSIONS

These pilot trial results suggest that, although stand and weight-bearing alone do not benefit pelvic organ functions after spinal cord injury, exercise in general may contribute at least partially to the lowering of bladder pressure and the increase in compliance that was seen previously with locomotor training, potentially through metabolic, humoral, and/or cardiovascular mechanisms. Thus, to maximize activity-based recovery training benefits for functions related to storage and emptying, an appropriate level of sensory input to the spinal cord neural circuitries controlling bladder and bowel requires task-specific stepping.

Effectiveness of a Goal-Based Intensive Rehabilitation in Parkinsonian Patients in Advanced Stages of Disease

BACKGROUND

Parkinsonian patients in advanced stages of disease suffer from many motor and non-motor symptoms, whose responsiveness to dopamine replacement therapy and deep brain stimulation is poor. It is necessary to find complementary strategies in order to improve the clinical conditions of patients in advanced Parkinson's disease (PD) stages.

OBJECTIVE

We aimed to understand whether an inpatient, motor-cognitive, multidisciplinary, aerobic, intensive and goal-based rehabilitation treatment (MIRT), specifically designed for PD, is effective for patients in advanced stages of disease.

METHODS

638 Parkinsonian patients, hospitalized to undergo a 4-week MIRT, were retrospectively identified. According to the Hoehn & Yahr (H&Y) scale, 496 were in H&Y stage 3 and 142 in H&Y stage 4-5. Outcome measures included: Unified Parkinson's Disease Rating Scale (UPDRS), Berg Balance Scale (BBS), Timed Up and Go Test (TUG), Six Minute Walk Test (6MWT), and Parkinson's Disease Disability Scale (PDDS).

RESULTS

At baseline all measures, except UPDRS IV, significantly worsened passing from H&Y stage 3 to H&Y stage 4-5 (p≤0.002 all). After rehabilitation all outcome measures significantly improved in both groups of patients (p < 0.0001 all). Comparing the amount of improvement in the two groups, significant differences were observed only for the changes in BBS and TUG (both p < 0.0001 after adjustment), with a better improvement in the H&Y stage 4-5 group.

CONCLUSIONS

A multidisciplinary, motor-cognitive, intensive and goal-based rehabilitation treatment, such as MIRT, could be an effective complementary treatment in PD patients in advanced stages of disease.

Land Plus Aquatic Therapy Versus Land-Based Rehabilitation Alone for the Treatment of Freezing of Gait in Parkinson Disease: A Randomized Controlled Trial

BACKGROUND

Freezing of gait (FOG) is one of the most disabling symptoms of Parkinson disease (PD). Different land-based rehabilitation approaches based on motor and cognitive strategies can be effective in treating FOG. Although there are data about the efficacy of aquatic therapy in ameliorating this phenomenon, no study has explored the combined effect of land-based therapies plus aquatic therapy in patients with PD who have FOG.

OBJECTIVE

The objective was to investigate the effectiveness of a multidisciplinary, intensive, motor-cognitive rehabilitation treatment (MIRT) in improving FOG and whether implementation with aquatic therapy (MIRT-AT) adds further benefits.

DESIGN

The design consisted of a single-blind, parallel-group, 1:1 allocation ratio, randomized trial.

SETTING

The Department of Parkinson Disease, Movement Disorders and Brain Injury Rehabilitation at "Moriggia-Pelascini" Hospital (Gravedona ed Uniti, Como, Italy) was used as the setting.

PARTICIPANTS

Sixty hospitalized patients with PD who had FOG in Hoehn and Yahr stage 2 or 5-3 were included.

INTERVENTION

Sixty patients with PD + FOG were randomly assigned to 2 groups: 30 underwent a 4-week MIRT and 30 underwent a 4-week MIRT-AT.

MEASUREMENTS

The primary outcome measure was the Freezing of Gait Questionnaire; secondary outcome measures were total Unified Parkinson Disease Rating Scale (UPDRS), UPDRS II, UPDRS III, Berg Balance Scale, Timed Up and Go Test, and 6-Minute Walk Test. These measures were assessed both at admission and discharge.

RESULTS

Participants in the 2 groups had similar age, sex distribution, Hoehn and Yahr stage, and most-affected side. At baseline, no difference in outcome measures was observed between the 2 groups. After treatment, a significant time effect was observed for all variables in both groups. No significant time × group interaction was observed. A between-group analysis showed nonsignificant differences between values at T1 and values at T0 for all variables.

LIMITATIONS

The limitations were the lack of a control group and follow-up.

CONCLUSIONS

We showed that a multidisciplinary, intensive, and goal-based rehabilitation treatment, such as MIRT, improves FOG in patients with PD. Although aquatic therapy could be considered a useful approach for treating FOG, it does not add further benefits to this kind of motor-cognitive rehabilitation.

Improvements in bladder, bowel and sexual outcomes following task-specific locomotor training in human spinal cord injury

OBJECTIVE

Locomotor training (LT) as a therapeutic intervention following spinal cord injury (SCI) is an effective rehabilitation strategy for improving motor outcomes, but its impact on non-locomotor functions is unknown. Given recent results of our labs' pre-clinical animal SCI LT studies and existing overlap of lumbosacral spinal circuitries controlling pelvic-visceral and locomotor functions, we addressed whether LT can improve bladder, bowel and sexual function in humans at chronic SCI time-points (> two years post-injury).

STUDY DESIGN

Prospective cohort study; pilot trial with small sample size.

METHODS

Eight SCI research participants who were undergoing 80 daily one-hour sessions of LT on a treadmill using body-weight support, or one-hour of LT and stand training on alternate days, as part of another research study conducted at the Kentucky Spinal Cord Injury Research Center, University of Louisville, were enrolled in this pilot trial. Urodynamic assessments were performed and International Data Set questionnaire forms completed for bladder, bowel and sexual functions at pre-and post-training time points. Four usual care (non-trained; regular at-home routine) research participants were also enrolled in this study and had the same assessments collected twice, at least 3 months apart.

RESULTS

Filling cystometry documented significant increases in bladder capacity, voiding efficiency and detrusor contraction time as well as significant decreases in voiding pressure post-training relative to baseline. Questionnaires revealed a decrease in the frequency of nocturia and urinary incontinence for several research participants as well as a significant decrease in time required for defecation and a significant increase in sexual desire post-training. No significant differences were found for usual care research participants.

CONCLUSIONS

These results suggest that an appropriate level of sensory information provided to the spinal cord, generated through task-specific stepping and/or loading, can positively benefit the neural circuitries controlling urogenital and bowel functions.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03036527.

Slow Versus Fast Robot-Assisted Locomotor Training After Severe Stroke: A Randomized Controlled Trial

BACKGROUND AND PURPOSE

Robot-assisted locomotor training on a bodyweight-supported treadmill is a rehabilitation intervention that compels repetitive practice of gait movements. Standard treadmill speed may elicit rhythmic movements generated primarily by spinal circuits. Slower-than-standard treadmill speed may elicit discrete movements, which are more complex than rhythmic movements and involve cortical areas.

OBJECTIVE

Compare effects of fast (i.e., rhythmic) versus slow (i.e., discrete) robot-assisted locomotor training on a bodyweight-supported treadmill in subjects with chronic, severe gait deficit after stroke.

METHODS

Subjects (N = 18) were randomized to receive 30 sessions (5 d/wk) of either fast or slow robot-assisted locomotor training on a bodyweight-supported treadmill in an inpatient setting. Functional ambulation category, time up and go, 6-min walk test, 10-m walk test, Berg Balance Scale, and Fugl-Meyer Assessment were administered at baseline and postintervention.

RESULTS

The slow group had statistically significant improvement on functional ambulation category (first quartile-third quartile, P = 0.004), 6-min walk test (95% confidence interval [CI] = 1.8 to 49.0, P = 0.040), Berg Balance Scale (95% CI = 7.4 to 14.8, P < 0.0001), time up and go (95% CI = -79.1 to 5.0, P < 0.0030), and Fugl-Meyer Assessment (95% CI = 24.1 to 45.1, P < 0.0001). The fast group had statistically significant improvement on Berg Balance Scale (95% CI = 1.5 to 10.5, P = 0.02).

CONCLUSIONS

In initial stages of robot-assisted locomotor training on a bodyweight-supported treadmill after severe stroke, slow training targeting discrete movement may yield greater benefit than fast training.

Enhancement of brain plasticity and recovery of locomotive function after lumbar spinal cord stimulation in combination with gait training with partial weight support in rats with cerebral ischemia

Lumbar spinal cord stimulation (LSCS) is reportedly effective for the recovery of locomotive intraspinal neural network, motor cortex and basal ganglia in animals with complete spinal cord injury and parkinsonism. We evaluated the effect of LSCS in combination with gait training on the recovery of locomotive function and brain plasticity using a rat model of brain ischemia. Adult male Sprague Dawley rats with ischemia were randomly assigned into one of four groups: sham treatment (group 1), LSCS only (group 2), LSCS with gait training and 50% (group 3) and 80% (group 4) of body weight support. Evaluations before randomization and 4weeks after intervention included motor scoring index, real-time PCR and Western blot. Motor scoring index was significantly improved after the intervention in groups 2 and 3. The ratio of phospho-protein kinase C (PKC) to PKC measured in the infarcted area tended to be higher in groups 3 and 4. Protein expression of mGluR2 and mRNA expression of mGluR1 measured in the contralateral cortex were lower in groups 3 and 4. The ratio of phospho-Akt to Akt and mRNA expression of vascular endothelial growth factor measured in the ischemic border zone were higher in group 2. The mRNA expression of MAP1b measured in the infarcted area was significantly higher in group 2. The findings suggest that LSCS and gait training with an adequate amount of body weight support may promote brain plasticity and facilitate the functional recovery.

Does Cognitive Impairment Affect Rehabilitation Outcome in Parkinson's Disease?

Background: The cognitive status is generally considered as a major determinant of rehabilitation outcome in Parkinson’s disease (PD). No studies about the effect of cognitive impairment on motor rehabilitation outcomes in PD have been performed before.

Objective: This study is aimed to evaluate the impact of cognitive decline on rehabilitation outcomes in patients with PD.

Methods: We retrospectively identified 485 patients with PD hospitalized for a 4-week Multidisciplinary Intensive Rehabilitation Treatment (MIRT) between January 2014 and September 2015. According to Mini Mental State Examination (MMSE), patients were divided into: group 1—normal cognition (score 27–30), group 2—mild cognitive impairment (score 21–26), group 3—moderate or severe cognitive impairment (score ≤ 20). According to Frontal Assessment Battery (FAB), subjects were divided into patients with normal (score ≥13.8) and pathological (score <13.8) executive functions. The outcome measures were: Unified Parkinson’s Disease Rating Scale (UPDRS), Parkinson’s Disease Disability Scale (PDDS), Six Minutes Walking Test (6MWT), Timed Up and Go Test (TUG) and Berg Balance Scale (BBS).

Results: All scales had worse values with the increase of cognitive impairment and passing from normal to pathological executive functions. After rehabilitation, all the outcome measures improved in all groups (p < 0.0001). Between groups, the percentage of improvement was significantly different for total UPDRS (p = 0.0009, best improvement in normal MMSE group; p = 0.019, best improvement in normal FAB group), and BBS (p < 0.0001, all pairwise comparisons significant, best improvement in patients with worse MMSE score; p < 0.0001, best improvement in patients with pathological FAB). TUG (p = 0.006) and BBS (p < 0.0001) improved in patients with pathological FAB score, more than in those with normal FAB score.

Conclusions: Patients gain benefit in the rehabilitative outcomes, regardless of cognition. Our data suggest that rehabilitation could be effective also in Parkinsonian subjects with cognitive impairment, as well as with dysexecutive syndrome.

Effects of exercise training on urinary tract function after spinal cord injury

Spinal cord injury (SCI) causes dramatic changes in the quality of life, including coping with bladder dysfunction which requires repeated daily and nightly catheterizations. Our laboratory has recently demonstrated in a rat SCI model that repetitive sensory information generated through task-specific stepping and/or loading can improve nonlocomotor functions, including bladder function (Ward PJ, Herrity AN, Smith RR, Willhite A, Harrison BJ, Petruska JC, Harkema SJ, Hubscher CH. J Neurotrauma 31: 819-833, 2014). To target potential underlying mechanisms, the current study included a forelimb-only exercise group to ascertain whether improvements may be attributed to general activity effects that impact target organ-neural interactions or to plasticity of the lumbosacral circuitry that receives convergent somatovisceral inputs. Male Wistar rats received a T9 contusion injury and were randomly assigned to three groups 2 wk postinjury: quadrupedal locomotion, forelimb exercise, or a nontrained group. Throughout the study (including preinjury), all animals were placed in metabolic cages once a week for 24 h to monitor water intake and urine output. Following the 10-wk period of daily 1-h treadmill training, awake cystometry data were collected and bladder and kidney tissue harvested for analysis. Metabolic cage frequency-volume measurements of voiding and cystometry reveal an impact of exercise training on multiple SCI-induced impairments related to various aspects of urinary tract function. Improvements in both the quadrupedal and forelimb-trained groups implicate underlying mechanisms beyond repetitive sensory information from the hindlimbs driving spinal network excitability of the lumbosacral urogenital neural circuitry. Furthermore, the impact of exercise training on the upper urinary tract (kidney) underscores the health benefit of activity-based training on the entire urinary system within the SCI population.

Therapy induces widespread reorganization of motor cortex after complete spinal transection that supports motor recovery

Reorganization of the somatosensory system and its relationship to functional recovery after spinal cord injury (SCI) has been well studied. However, little is known about the impact of SCI on organization of the motor system. Recent studies suggest that step-training paradigms in combination with spinal stimulation, either electrically or through pharmacology, are more effective than step training alone at inducing recovery and that reorganization of descending corticospinal circuits is necessary. However, simpler, passive exercise combined with pharmacotherapy has also shown functional improvement after SCI and reorganization of, at least, the sensory cortex. In this study we assessed the effect of passive exercise and serotonergic (5-HT) pharmacological therapies on behavioral recovery and organization of the motor cortex. We compared the effects of passive hindlimb bike exercise to bike exercise combined with daily injections of 5-HT agonists in a rat model of complete mid-thoracic transection. 5-HT pharmacotherapy combined with bike exercise allowed the animals to achieve unassisted weight support in the open field. This combination of therapies also produced extensive expansion of the axial trunk motor cortex into the deafferented hindlimb motor cortex and, surprisingly, reorganization within the caudal and even the rostral forelimb motor cortex areas. The extent of the axial trunk expansion was correlated to improvement in behavioral recovery of hindlimbs during open field locomotion, including weight support. From a translational perspective, these data suggest a rationale for developing and optimizing cost-effective, non-invasive, pharmacological and passive exercise regimes to promote plasticity that supports restoration of movement after spinal cord injury.

Relationship between ASIA examination and functional outcomes in the NeuroRecovery Network Locomotor Training Program

OBJECTIVE

To determine the effects of locomotor training on: (1) the International Standards for Neurological Classification of Spinal Cord Injury examination; (2) locomotion (gait speed, distance); (3) balance; and (4) functional gait speed stratifications after chronic incomplete spinal cord injury (SCI).

DESIGN

Prospective observational cohort.

SETTING

Outpatient rehabilitation centers in the NeuroRecovery Network (NRN).

PARTICIPANTS

Individuals (n=225) with American Spinal Injury Association Impairment Scale (AIS) grade C or D chronic motor incomplete SCI having completed locomotor training in the NRN.

INTERVENTION

The NRN Locomotor Training Program consists of manual-facilitated body weight-supported standing and stepping on a treadmill and overground.

MAIN OUTCOME MEASURES

AIS classification, lower extremity pin prick, light touch and motor scores, ten-meter walk and six-minute walk tests, and the Berg Balance Scale.

RESULTS

Significant gains occurred in lower extremity motor scores but not in sensory scores, and these were only weakly related to gait speed and distance. Final Berg Balance Scale scores and initial lower extremity motor scores were positively related. Although 70% of subjects showed significantly improved gait speed after locomotor training, only 8% showed AIS category conversion.

CONCLUSIONS

Locomotor training improves gait speed to levels sufficient for independent in-home or community ambulation after chronic motor incomplete SCI. Changes in lower extremity motor and sensory scores do not capture the full extent of functional recovery, nor predict responsiveness to locomotor training. Functional classification based on gait speed may provide an effective measure of treatment efficacy or functional improvement after incomplete SCI.

Physical rehabilitation as an agent for recovery after spinal cord injury

The initial level of injury and severity of volitional motor and clinically detectable sensory impairment has been considered the most reliable for predicting neurologic recovery of function after spinal cord injury (SCI). This consensus implies a limited expectation for physical rehabilitation interventions as important in the facilitation of recovery of function. The development of pharmacologic and surgical interventions has always been pursued with the intent of altering the expected trajectory of recovery after SCI, but only recently physical rehabilitation strategies have been considered to improve recovery beyond the initial prognosis. This article reviews the recent literature reporting emerging activity-based therapies that target recovery of standing and walking based on activity-dependent neuroplasticity. A classification scheme for physical rehabilitation interventions is also discussed to aid clinical decision making.

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.

Neuroplasticity after spinal cord injury and training: an emerging paradigm shift in rehabilitation and walking recovery

Physical rehabilitation after spinal cord injury has been based on the premise that the nervous system is hard-wired and irreparable. Upon this assumption, clinicians have compensated for irremediable sensorimotor deficits using braces, assistive devices, and wheelchairs to achieve upright and seated mobility. Evidence from basic science, however, demonstrates that the central nervous system after injury is malleable and can learn, and this evidence has challenged our current assumptions. The evidence is especially compelling concerning locomotion. The purpose of this perspective article is to summarize the evidence supporting an impending paradigm shift from compensation for deficits to rehabilitation as an agent for walking recovery. A physiologically based approach for the rehabilitation of walking has developed, translating evidence for activity-dependent neuroplasticity after spinal cord injury and the neurobiological control of walking. Advanced by partnerships among neuroscientists, clinicians, and researchers, critical rehabilitation concepts are emerging for activity-based therapy to improve walking recovery, with promising clinical findings.

Voluntary exercise increases neurotrophin-3 and its receptor TrkC in the spinal cord

We have evaluated changes in the expression of neurotrophin-3 (NT-3) and its tyrosine kinase C (TrkC) receptor in the neuromuscular system as a result of voluntary physical activity. We assessed changes in the mRNAs and proteins for NT-3 and TrkC in the lumbar spinal cord and associated soleus muscle following 3 and 7 days of voluntary wheel running. We used quantitative Taqman RT-PCR to measure mRNA and ELISA to assess protein levels. NT-3 mRNA and protein levels increased in the spinal cord to reach statistical significance after 7 days of exercise compared to sedentary control rats. Immunohistochemical analyses localized the elevated NT-3 to the substantia gelatinosa (SG) and nucleus of the dorsal horn. TrkC mRNA levels were significantly elevated in the spinal cord after 3 and 7 days of running. In the soleus muscle, NT-3 mRNA levels and its receptor TrkC were elevated after 3 days, while NT-3 protein levels remained unaffected. The results demonstrate that voluntary exercise has a differential effect on NT-3 as well as its receptor TrkC in the neural and muscular components of the neuromuscular system, and emphasize the role of voluntary activity on the spinal cord and muscle.

Central pattern generation of locomotion: a review of the evidence

Neural networks in the spinal cord, referred to as "central pattern generators" (CPGs), are capable of producing rhythmic movements, such as swimming, walking, and hopping, even when isolated from the brain and sensory inputs. This article reviews the evidence for CPGs governing locomotion and addresses other factors, including supraspinal, sensory, and neuromodulatory influences, that interact with CPGs to shape the final motor output. Supraspinal inputs play a major role not only in initiating locomotion but also in adapting the locomotor pattern to environmental and motivational conditions. Sensory afferents involved in muscle and cutaneous reflexes have important regulatory functions in preserving balance and ensuring stable phase transitions in the locomotor cycle. Neuromodulators evoke changes in cellular and synaptic properties of CPG neurons, conferring flexibility to CPG circuits. Briefly addressed is the interaction of CPG networks to produce intersegmental coordination for locomotion. Evidence for CPGs in humans is reviewed, and although a comprehensive clinical review is not an objective, examples are provided of animal and human studies that apply knowledge of CPG mechanisms to improve locomotion. The final section deals with future directions in CPG research.

How the science and engineering of spaceflight contribute to understanding the plasticity of spinal cord injury

Space programs support experimental investigations related to the unique environment of space and to the technological developments from many disciplines of both science and engineering that contribute to space studies. Furthermore, interactions between scientists, engineers and administrators, that are necessary for the success of any science mission in space, promote interdiscipline communication, understanding and interests which extend well beyond a specific mission. NASA-catalyzed collaborations have benefited the spinal cord rehabilitation program at UCLA in fundamental science and in the application of expertise and technologies originally developed for the space program. Examples of these benefits include: (1) better understanding of the role of load in maintaining healthy muscle and motor function, resulting in a spinal cord injury (SCI) rehabilitation program based on muscle/limb loading; (2) investigation of a potentially novel growth factor affected by spaceflight which may help regulate muscle mass; (3) development of implantable sensors, electronics and software to monitor and analyze long-term muscle activity in unrestrained subjects; (4) development of hardware to assist therapies applied to SCI patients; and (5) development of computer models to simulate stepping which will be used to investigate the effects of neurological deficits (muscle weakness or inappropriate activation) and to evaluate therapies to correct these deficiencies.

Significance of load receptor input during locomotion: a review

A basic aspect of the neuronal control of quadrupedal locomotion of cat and of bipedal stance and gait of humans concerns the antigravity function of leg extensors. In humans proprioceptive reflexes involved in the maintenance of body equilibrium depend on the presence of contact forces opposing gravity. Extensor load receptors are thought to signal changes of the projection of body's centre of mass with respect to the feet. According to observations in the cat, this afferent input probably arises from Golgi tendon organs and represents a newly discovered function of these receptors in the regulation of stance and gait. From these experiments it can be concluded that during locomotion there is a closing of Ib inhibitory and an opening of Ib extensor facilitatory paths. In humans evidence for a significant contribution of load receptor contribution to the leg muscle activation came from immersion experiments. Compensatory leg muscle activation depends on the actual body weight. Also during gait the strength of leg extensor activation during the stance phase is load dependent. In patients with Parkinson's disease there is a reduced load sensitivity and decreased leg extensor activation, which might contribute to the movement disorder. Recent experiments in paraplegic patients show that the beneficial effects of a locomotor training critically depends on the initial degree of body unloading and reloading during the course of the training period.

Neural control of locomotion: sensory control of the central pattern generator and its relation to treadmill training

Many studies have shown that a special treadmill training is effective in restoring locomotor function in cats with a complete spinal lesion. In the last few years it has become possible to regain some locomotor activity in patients suffering from a spinal cord injury through an intense training on a treadmill, as in cats. The ideas behind this approach owe much to insights derived from studies on spinalized animals. The neural system responsible for the locomotor restoration in both cats and humans is thought to be located at spinal level and is referred to as the central pattern generator. The evidence for such a spinal central pattern generator is reviewed in part 1. An important element in the treadmill training for both spinal injured cats and humans is the provision of adequate locomotor related sensory input, which can possibly activate and/or regulate the spinal locomotor circuitry. This part of the review deals with the afferent control of the central pattern generator. Furthermore, the results of treadmill training for both cats and humans and their relation to sensory input are treated. These insights can possibly contribute to the design of a better treadmill training program for the rehabilitation of gait in spinal cord injured patients. Copyright 1998 Elsevier Science B.V. All rights reserved