Developing Clinical Evidence for Locomotor Training

Locomotor training is an emerging rehabilitation intervention to help patients who have spinal cord injuries or who are recovering from stroke walk again. The basis for the intervention lies in understanding the neurobiology of walking and the nervous system's capacity for activity-dependent plasticity.

Important questions and controversies have arisen in light of the emerging knowledge about the neurobiology of human locomotion. Clarifying the issues is critical to the success of this promising intervention.

Hugues Barbeau, PhD, PT, a leading neuroscientist and physical therapist at the School of Physical and Occupational Therapy at McGill University in Montreal, described locomotor training as "one of the evidence-based clinical approaches that will be used in the 21st century to enhance recovery of posture and locomotion in stroke, spinal cord injury, and other neurologic disorders."¹

In contrast to Barbeau's prediction, however, a review by Anne M. Moseley, PhD, PT, and colleagues that appeared in the July 2003 issue of the Cochrane Database of Systematic Reviews concluded that treadmill training and body weight support (BWS) is as effective as--but not better than--other treatment interventions for post-stroke rehabilitation of walking.² The review found that existing evidence about locomotor training is inconclusive; at best, it appears to have the highest level of effectiveness in patients recovering from stroke who already can walk independently but whose walking may be affected by persistent defects, such as slowness.

Despite these equivocal findings, the development, manufacturing, and marketing of BWS systems for clinical use have grown rapidly. A search on the World Wide Web for partial-weight-bearing or unweighting systems shows that at least 7 companies are currently marketing BWS systems. As a result, there is an influx of equipment into clinics in the absence of the evidence-based information needed to use it effectively. Do Barbeau's prediction, the findings of Moseley and associates, and a rapid growth in access and clinical use of the BWS treadmill (BWST) appear incongruent?

RETRAINING A PERSON TO WALK

Locomotor training refers to an intervention for retraining patients to walk after neurologic injury. The intervention developed out of the neuroscientific examination of the role of the spinal cord in the physiologic control of walking and activity-dependent plasticity, which is the nervous system's capacity for learning (Figures 1 and 2).

The goals of locomotor training are to capitalize on the intrinsic mechanisms of the CNS that respond to sensory input associated with walking to generate a stepping response and on the ability of the CNS to learn through intensive, task-specific repetition and practice.¹ Researchers successfully used this strategy to train cats with complete midthoracic spinal cord transections to hind-limb step. Manual assistance to load the hind limbs and approximate the kinematics of stepping was used along with a sling linked to an overhead supportfor partial weight support and a treadmill to provide a controlled, repetitive training environment.^3,4 This training facilitated the sensory experience of walking and, with repetition, generated the motor response of stepping. Following months of intense practice, the spinalized cats learned to hind-limb step on the treadmill without any supraspinal support. From this basic science foundation, the BWS system and the BWST emerged as tools for retraining humans in walking after neurologic injury.

When the animal research was applied to humans, various BWS devices were engineered to support human participants in laboratory settings.^5-7 As the research expanded, the available market for BWS systems for rehabilitation in clinical practice grew as well. New terms for identifying the specialty equipment and the training have been coined, such as "body-weight-supported treadmill training" and "partial-weight-supported therapy." By emphasizing the equipment, however, these terms mask the critical elements of the training provided by the clinician. While the equipment allows for greater ease, consistency, and control, it is not the active therapeutic ingredient that yields benefit; it is simply a tool.

In fact, the training can be provided either while using the BWST or while walking over ground. The theoretic framework for therapeutic intervention--not the equipment--provides the therapist with the basis for decision making and delivery of effective care. Therefore, the active and essential ingredients responsible for a therapeutic effect reside within the therapeutic framework of locomotor training.

Locomotor training requires that clinical researchers apply the same model used in animals to humans.⁸ Elements of locomotor training in animal models facilitated the kinematics, loading, and spatial-temporal patterns associated with walking, task-specific training, and intensive practice and repetition. Researchers in neurophysiology and physical rehabilitation have begun to examine and clarify similar elements that can be applied to patients recovering from stroke and spinal cord injuries. Their findings hold promise for application in clinical training models.

For example, researchers have observed improved leg muscle coordination patterns in patients with spinal cord injuries while they were walking with manual-assisted locomotor training using the BWST at speeds that began to approach that of a normal gait.⁹ Likewise, improved muscle-phasing patterns were observed at faster gait speeds in patients recovering from stroke who were trained at speeds approximating those of normal walking (2 mph).¹⁰ This evidence suggests that in training these patients, researchers and clinicians should use relatively normal walking speeds rather than the slower speeds traditionally used in gait training.

Furthermore, improved symmetry and muscle coordination were observed in persons with spastic paresis during locomotor training when load bearing through the legs with BWS equipment was maximized and load bearing through the arms was minimized.¹¹ This suggests that upper limb loading should be minimized during training with a BWS system or during training overground (with or without BWS equipment). Alternative, patient-specific training strategies that examine speed protocols; various methods of weight support; and manual-versus-robotic assistance to improve balance, muscle activation, and gait continue to be examined.¹²

Another consideration that must be addressed in evaluating and documenting the value of locomotor training is whether the variations that exist in the equipment itself influence the therapeutic process and outcomes of locomotor training for specific patient populations. The literature addressing this question is scarce.^13,14 A need exists for manufacturers and researchers to better inform patients and clinicians about the capacity of the available therapeutic tools and equipment.

NEED FOR CLINICAL GUIDELINES

Whether Barbeau's prediction about the value of locomotor training in rehabilitation comes to pass relies on our perseverance in developing scientifically based clinical guidelines that empower therapists in their clinical decision making. Such evidence would allow clinicians to:

* Select candidates for training based on the specific injury or disease that they are recovering from, on the severity of impairment, and on whether they are dealing with a constellation of impairments.

* Decide the optimal time to begin rehabilitation therapy during the recovery phase.

* Monitor treatment dosage for efficient delivery and maximum benefit.

* Incorporate adjunctive therapies, such as strength training or electrical stimulation,¹⁵ or deliver the training with pharmacotherapies that promote recovery.¹⁶

* Identify medical precautions for specific patients.

* Plan therapy based on expected outcomes for walking and secondary benefits, such as physiologic health, fitness, and quality of life.

* Select and safely use therapeutic equipment and assistive devices.

TOWARD CAPTURE OF EVIDENCE

With the technologic and research resources available to us in the 21st century, the goal of developing clinical guidelines and evidence-based practices for locomotor training is attainable. But what of existing evidence? Although Moseley and colleagues² have suggested that definitive evidence of the benefit of treadmill training and the BWS system does not exist, those patients recovering from stroke who could walk independently because of the training appeared to benefit.

The 11 studies reviewed by the team differed in terms of research design; patient characteristics (including stroke severity); time from stroke to initiation of the intervention; training parameters for intensity, frequency, and duration; training protocols (ie, incorporating overground training); training equipment; and delivery environment. Their findings and collective analysis, however, do lend answers to important questions about efficacy and effectiveness in comparing one intervention with another.

We suggest that these studies are a first layer of investigation and propose that a far-reaching research plan be developed that sequentially addresses issues of impairment severity, chronicity, level of disability, and cognitive capacity, as well as dosage and treatment protocol issues. Research that steadfastly pursues targeted questions and hypotheses that address the multiple factors affecting clinical success with locomotor training will provide the practitioner with the knowledge needed for clinical decision making. All such factors have yet to be examined and tested in a systematic way.

TRAINING DATA NEEDED ON SPINAL CORD INJURIES

No systematic review similar to that in the Cochrane Database of Systematic Reviews has been published about spinal cord injury rehabilitation and outcomes from locomotor training using the BWST. The variability in research design and analysis of individual studies to date is similar to that seen in studies of patients receiving rehabilitation after stroke. The application of locomotor training in persons with complete spinal cord injuries to discern the mechanisms of recovery and the health benefits of intervention remains in the hands of research institutions.^17,18

To date, studies examining the effects of locomotor training in persons with incomplete spinal cord injuries show promise for improved muscle activation and coordination, reflex modulation, balance, gait speed, endurance, and independence.^19-25 We still need to identify the best candidates for locomotor training, the best use of adjunct therapies,^15,16,26,27 the best sequence of therapies, and the best timing and dosage of therapies. Just as for stroke, the "who," "what," "when," and "where" of clinical guidelines for locomotor training post-spinal cord injury must be established.

The study by Moseley and colleagues and the current literature are congruent with Barbeau's prediction that locomotor training provides benefit after spinal cord injury. Barbeau's optimism about its value and use in the coming years is grounded in findings from the current phase of early research.

Is the popularity of BWS systems in clinical practice consistent with Barbeau's prediction and the findings of Moseley and her team? Yes and no. We recommend that practicing therapists use caution and have patience while rehabilitation researchers pursue both the evidence for the value of locomotor training and the processes that will be required for its applicability in clinical practice.

On the other hand, evidence-based practice is neither exclusive to researchers nor linear in nature. Rather, according to Sackett and colleagues,²⁸ evidence-based practice means "integrating individual clinical expertise with the best available external clinical evidence from systematic research." Close collaboration and exchange of information among researcher, clinician, and patient will result in the "best" evidence.

Clinical experimentation and use of BWS equipment in the clinic is another opportunity to investigate and explore the effectiveness of locomotor training. The final caution here, as stated, is that the effectiveness of locomotor training lies in the therapeutic framework generated by the clinician, not in the equipment itself.

We have identified a prediction for future rehabilitation practice and the capacity to produce clinical guidelines through research. We also have reported a growth in manufacturers of therapeutic BWS equipment, which already is be-ing used in clinical settings. Furthermore,we have identified a groundwork of literature on locomotor training that is expanding. Interpretation of studies should be approached cautiously, with an eye for their impact on development of locomotor training therapies and guidelines. Otherwise, a generation of BWS systems may be used indiscriminately and ultimately discarded as ineffective. *

References

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2. Moseley AM, Stark A, Cameron ID, Pollock A. Treadmill training and body weight support for walking after stroke. Cochrane Database Syst Rev. 2003;(3):CD002840.

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4. Barbeau H, Rossignol S. Recovery of locomotion after chronic spinalization in the adult cat. Brain Res. 1987;412:84-95.

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16. Edgerton VR, Tillakaratne NJ, Bigbee AJ, et al. Plasticity of the spinal neural circuitry after injury. Annu Rev Neurosci. 2004;27:145-167.

17. Dobkin BH, Edgerton VR, Fowler E, Hodgson J. Training induces rhythmic locomotor EMG patterns in a subject with complete spinal cord injury. Neurology. 1992;42(suppl 3):207-208.

18. Harkema SJ, Hurley SL, Patel UK, et al. Human lumbosacral spinal cord interprets loading during stepping. J Neurophysiol. 1997;77:797-811.

19. Wernig A, Muller S, Nanassy A, Cagol E. Laufband therapy based on "rules of spinal locomotion" is effective in spinal cord injured persons. Eur J Neurosci. 1995;7:823-829.

20. Wernig A, Nanassy A, Muller S.Laufband (treadmill) therapy in incomplete paraplegia and tetraplegia. J Neurotrauma. 1999;16:719-726.

21. Gardner MB, Holden MK, Leikauskas JM, Richard RL.Partial body weight support with treadmill locomotion to improve gait after incomplete spinal cord injury: a single-subject experimental design. Phys Ther. 1998;78:361-374.

22. Nymark J, DeForge D, Barbeau H, et al. Body weight support treadmill gait training in the subacute recovery phase of incomplete spinal cord injury. J Neurol Rehab. 1998;12:119-138.

23. Behrman AL, Harkema SJ. Locomotor training after human spinal cord injury: a series of case studies. Phys Ther. 2000;80:688-700.

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25. Protas EJ, Holmes SA, Qureshy H, et al.Supported treadmill ambulation training after spinal cord injury: a pilot study. Arch Phys Med Rehabil. 2001;82:825-831.

26. Ladouceur M, Barbeau H. Functional electrical stimulation-assisted walking for persons with incomplete spinal injuries: changes in the kinematics and physiological cost of overground walking. Scand J Rehabil Med. 2000;32:72-79.

27. Ladouceur M, Pepin A, Norman KE, Barbeau H. Recovery of walking after spinal cord injury. Adv Neurol. 1997;72:249-255.

28. Sackett DL, Rosenberg WM, Gray JA, et al. Evidence based medicine: what it is and what it isn't. BMJ. 1996;312:71-72.

Andrea L. Behrman, PhD, PT, is associate professor of physical therapy and an investigator with the Brooks Center for Rehabilitation Studies at the University of Florida in Gainesville. She also is an associate investigator in the VA Brain Rehabilitation Research Center and the VA Rehabilitation Outcomes Research Center at the Malcolm Randall VA Medical Center in Gainesville.

Mary T. Thigpen, PhD, PT, is assistant professor of physical therapy at the University of North Florida in Jacksonville.

Figure 1.

Locomotor training assisted by manual trainers, partial body weight support, and the treadmill for a patient with an incomplete spinal cord injury.

Figure 2.

Locomotor training continues while walking over ground.