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Spring 2003

Body-Weight-Supported Treadmill Training

(see photo of patient using the system.)

Significant advances in neurological research have produced growing evidence that spinal cord neurons have a capacity for learning or "memory" that is independent from the brain and can be used to improve walking ability in people with paralysis due to SCI. There is also hope that this capability might be harnessed to enhance spinal cord regeneration strategies.
Animal research in the 1960s suggested that cats with transected spinal cords could produce stepping patterns after several weeks of body-weight-supported treadmill training (BWSTT), in which the cat was partially supported in a sling and its hind limbs were manually assisted on a treadmill. This ability was attributed to a so-called central pattern generator, said to be produced in the lumbosacral spinal cord below the injury in response to sensory information associated with locomotion. This research into spinal cord "learning" has led to investigations of a possible central pattern generator in humans.

In 1992 Wernig and Muller reported that treadmill locomotion with body-weight support improved walking in persons with SCI. In their study, eight individuals with incomplete SCI were trained on a driven treadmill for 1½ to 7 months, 5 days a week, 30 to 60 minutes daily, starting 5 to 20 months after injury. Five patients had complete functional paralysis in one leg when tested in a resting position. As a result of the training program, initial body-weight support of 40% was reduced to 0%, and the walking distance increased significantly. In addition, patients were able to walk on a static surface even though voluntary activity remained absent in the paralyzed leg when tested at rest. Wernig and Muller concluded that the patients were manifesting complex reflex motor patterns at the spinal level.

In another interesting study of 14 subjects conducted in Switzerland, Dietz and others (1998) showed that spontaneous recovery was not responsible for the locomotion improvements observed following BWSTT, and a limited contribution came from the stretch reflex. Two patients with incomplete low level SCI (cauda equina) improved clinically with treadmill training in this study despite almost no EMG activity in the lower leg muscles before or after training, suggesting that improvements were due to possible changes at the tendons or joints. The subjects with complete paraplegia were able to show a locomotor pattern during BWSTT when leg movements were assisted externally by investigators; however, no voluntary movements resulted from this leg muscle activation over the 12 weeks of daily training, and the EMG activation was small and did not improve beyond 4 weeks of training.

A 5-site, NIH-funded, randomized clinical trial called "Treadmill Training for SCI" is aimed at determining if 12 weeks of BWSTT with regular physical therapy results in greater improvement in locomotion than regular physical therapy alone in recently injured patients with incomplete SCI. Centered at UCLA, the study is still in progress. (For further information, contact the Principal Investigator, Bruce Dobkin, MD, at 310-306-6500 or bdobkin@ucla.edu).

In the highly publicized case of a man with a C2 injury due to an equestrian accident, McDonald et al. (2002) reported that late recovery was possible following an intensive program of cycling, aqua therapy, electrical stimulation, and range of motion and breathing exercises. After three years of this activity-based recovery program (5 to 8 years after injury), the patient had improvements in his physical condition (reversal of osteoporosis, improved cardiovascular endurance, enhanced muscle mass, reported sensory and motor function changes) but not in bladder, bowel or sexual function, and he is still vent-dependent. (The reader should note that this was a single case report and not a controlled study.)

While awaiting the results of ongoing studies, the cases reported in the literature thus far suggest that in persons with motor incomplete SCI, a higher level of overground mobility may be gained if they receive locomotor training using BWSTT. In the UWMC's Rehabilitation Therapy program, selected patients with stroke, MS, or incomplete (ASIA C or D) paraplegia may receive BWSTT on the Lite Gait system (Mobility Research). Patients with certain conditions, such as spinal instability, weight-bearing precautions, or postural hypotension (blood pressure drops dangerously when upright) are not good candidates for BWSTT.

Since the Lite Gait harness can carry up to 100% of a patient's weight and the treadmill can go much slower than standard treadmills, patients can start gait training earlier and progress faster, and possibly further, than with standard therapy. Even though the wheelchair may remain the primary method of mobility, locomotion may improve, and an increase in overall health and fitness-improved circulation, strength, cardiovascular health, bone density and weight management-make this a desirable treatment option for appropriate patients.

Diana D. Cardenas, MD

(If you are interested in BWSTT, please call UWMC's SCI Clinic at 206-598-4295 or Harborview's Comprehensive Outpatient Rehabilitation Program at 206-731-2140 for an evaluation.)

References