Many aggressive rehabilitation programs have incorporated body-weight-supported (BWS) treadmill training to enhance ambulatory ability after spinal cord injury. This training apparently develops new function-restoring neuronal networks and triggers the spinal-cord’s “central-pattern generator,” a sort of brain within the spinal cord that can sustain lower-limb repetitive movement, such as walking, independent of direct brain control. The article summarizes various research studies evaluating the impact of treadmill training. Because specific procedures often vary considerably, it is hard to over-generalize the results. Some studies suggest considerable benefits, and others do not.

STUDIES:

A key pioneer in developing treadmill training for SCI is Dr. Anton Wernig (Karlsbad, Germany), a scientist I’ve met who seems to have almost a Zen-like appreciation of movement in those with SCI (www.meb.uni-bonn.de/wernig). In 1992, Wernig and colleagues reported the results of training eight individuals with incomplete SCI with a variable speed treadmill, on which the individual was partially supported with a harness (Paraplegia 1992; 30(4)).

To enhance correct ambulatory movements, therapists assisted the subjects. With practice, support was reduced from 40% to 0%. Starting 5-20 months after injury, patients trained for 1.5-7 months for five days a week, 30-60 minutes daily. All improved their ambulation, including the ability “to walk short distances, to bear their body weight fully without knee-stabilizing braces and to climb stairs while needing only a handrail and one cane.”

In 1995, the investigators reported the results of a larger study evaluating such training in 44 patients with chronic SCI (Eur J Neuroscience 1995; 7(4)). The patients had sustained their injuries ½ -18 years before initiating 3-20 weeks of training. Most improved their ambulation. Fourteen of 18 patients learned to walk without help from others compared to 1 of 14 of those who received conventional therapy.

Follow-up assessments indicated that patients who had improved to the point of walking independently continued to use their new found abilities over time as a part of every-day life. In addition, after training, 36 of the 44 patients were capable of stair walking compared to only six before. Of acutely injured patients, 92% who used wheelchairs became independent walkers after treadmill training compared to only 50% after conventional therapy.

Dr. A. L. Hicks et al. (Hamilton, Ontario) studied the effects of long-term, BWS treadmill training in 14 subjects (11 men, 3 women) with chronic, incomplete SCI (Spinal Cord 2005; 43(5)). The time since injury ranged from 1.2 to 24 years. Subjects exclusively trained on the treadmill three times a week for a total of 144 sessions over a 12-15 month period. All subjects who completed the program improved their treadmill walking ability, including a 54% reduction in body-weight support, a 180% improvement in walking speed, and a 335% in the distance covered per session (from 221 to 961 meters).

The improvements were associated with increased life satisfaction and physical function; and also improved muscle mass and composition, and blood-lipid profiles and glucose-tolerance consistent with a lowered risk of SCI-related diabetes and cardiovascular disease. Some improvements diminished over time as subjects discontinued training. Although such training appeared to reverse post-injury muscle atrophy, it did not prevent bone loss. The program did not include over ground walking. (Spinal Cord 2005; 43(11)).

Dr. Bruce Dobkin (Los Angeles, Calif) and associates compared high-speed BWS treadmill training with a control program of aggressive over-ground mobility training (Neurology 2006; 66(4)).  Injured for fewer than eight weeks, 146 subjects were recruited from six centers. Subjects were randomized to a 12-week treadmill or control program (e.g., aided over-ground walking, etc.), both providing an hour of training per session for at least 45 sessions over 12 weeks or until reaching a defined level of restored ambulation. The investigators were unable to detect differences in benefits accruing between the treadmill and control groups. In a later commentary, Wernig noted this outcome was to be expected due to equal amounts of upright walking.

Dr. Marcus Wirz (Zurich, Switzerland) and colleagues (U.S.A. and Germany) treated 20 subjects (18 men, 2 women) with incomplete, chronic injuries with BWS treadmill training using the Lokomat, a robotic treadmill device (www.hocoma.ch) that minimizes the need for assisting therapists (Arch Phys Med Rehabil 2005; 86). The time elapsing since injury and training ranged between 2-17 years, and participants’ age ranged from 16 to 64 years. Sixteen had some ambulatory ability before training.  

The program consisted of three to five 45-minute sessions per week for eight weeks. Ambulatory ability was assessed by a variety of tests, most of which, - but not all - demonstrated improvement. Subjects showed better gait speed, endurance, and performance of functional tasks.

Dr. Patricia Winchester et al. (Dallas) examined the effects of 12 weeks of BWS treadmill training using the Lokomat on the brain’s neuronal activity in four men with incomplete cervical injuries (Neurorehabil Neural Repair 2005; 19(4)).  These subjects sustained their injuries 14 weeks to four years before starting the program and had sufficient range of motion to stand and some ankle and toe movement.

The study’s goal was to measure the differences in brain neuronal activity before and after training - i.e., does treadmill training promote walking through brain reprogramming? To measure the intensity of walking-associated brain activity, subjects flexed their ankles and curled their toes while keeping their heads motionless within a MRI device. After 12 weeks, three of the four subjects demonstrated improved walking, and all exhibited increased activity in brain areas associated with walking.

Drs. Sarah Thomas and Monica Gorassini (Alberta, Canada) studied the effects of BWS treadmill training on brain-to-muscle nerve transmission through spinal pathways in individuals with chronic, incomplete injuries (J Neurophysiol 2005; 94(4)).  Age and time since injury ranged from 29-78 years and 0.6-28 years, respectively. On average, the subjects trained for an hour five times weekly for nearly 17 weeks.

The capacity of these pathways to transmit nerve signals was measured by stimulating brain areas associated with specific leg muscles through a transcranial-magnetic-stimulation (TMS) device placed over the scalp that activates descending neuronal pathways. The amount of signal getting through to the leg muscles was then measured by a device in which electrodes are placed on the skin over a muscle to detect electrical activity. Results indicated that the treadmill training improved ambulatory ability, which was associated with an increase in the transmission capacity between brain and leg muscles.

Miami Project’s Dr. Edelle Field-Fote et al. evaluated the effects of BWS, FES-assisted (functional electrical stimulation) treadmill training on ambulation in 19 subjects with incomplete, chronic injuries (Arch Phys Med Rehabil 2001; 82(6)). Training consisted of three-times-a-week, 1½ -hour sessions for three months. All subjects improved walking speed and lower extremity strength.  

Later, the investigators reported the results of a study in which 27 individuals with incomplete SCI were randomly assigned to the following groups: 1) treadmill training with manual assistance, 2) treadmill training with FES stimulation, 3) over-ground training with FES stimulation, and 4) treadmill training using robotic assistance (J Neurol Phys Ther 2005; 29(3)). Benefits seemed comparable across approaches. 

CONCLUSION

Reflecting the ancient adage that a journey of a thousand miles begins with a single step, no-nonsense, hard-work treadmill training is increasingly being incorporated into a variety of rehabilitation programs to maximize restored function after SCI.  Although questions linger concerning the magnitude of its impact, numerous studies suggest that it promotes some ambulatory recovery.

However, many “the-devil-is-in-the-details” variables confound the comparison of results between studies.

Adapted from an article appearing in the February 2007 Paraplegia News (For subscriptions, call 602-224-0500 or go to www.pn-magazine.com).

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