Split-belt Treadmill Therapy
A split-belt treadmill features two separate belts running alongside each other, one for each leg. The two belts can move together or at independent speeds. If they move at independent speeds, this unusual situation causes your brain to receive an error signal. The brain and nervous system then use the feedback of this signal to adjust your walking pattern. Because each leg has to adapt to a different speed, it forces your legs to adopt individual stride lengths in order to keep balance. The cerebellum (a part of your brain that is important for motor control) recalls this new message even after the treadmill has stopped.1 In other words, your brain adapts to a peculiar situation on the treadmill and once you step off it, you continue to walk as you did on the treadmill. This form of gait rehabilitation is effective because the brain naturally adapts and modifies the walking pattern (or gait) based on stimulus. In this way, by repetition and instruction, the brain can 'reawaken' the old gait, at least for a short while.
In practice, split-belt treadmill therapy happens like this: if you have a defective gait, the difference in movement between your two legs is measured and analysed. Once the results are known, the split-belt can be programmed so that the leg with the shorter step-length is trained at the slower speed. This means that the leg that usually takes a shorter step will take an even shorter step, which forces the brain and nervous system to compensate for the exaggerated assymetry and adjust by taking longer strides. This will result in the difference in step-length becoming smaller.2 Once you are back on solid ground, you should see a difference in your walking pattern. The change in gait caused by the treadmill will result in a more normal step-length and, consequently, in a more normal gait.
Possible benefits of Split-belt Treadmill Therapy for stroke
After a stroke, there might be a reduction in the mobility of one or more limbs on one side of the body, a condition called hemiparesis. If it affects one of the legs, it will usually result in the unimpaired limb having a shorter step-length compared to the impaired limb.3 This leads to difficulty walking, or an inability to walk. In 2007, a trial at John Hopkins School of Medicine tested a group of 13 people, who had had strokes more than six months prior to the study, against 13 control subjects. They found that the stroke survivors temporarily adjusted their gait after a 15-minute session on the treadmill, which suggests that people who have had strokes are able to adapt their limb coordination using this kind of treatment.4 According to a 2010 study by the same researchers,
‘Split-belt and limb-weighting locomotor adaptation studies show that adults with chronic stroke are capable of improving weight-bearing and spatiotemporal symmetry, at least temporarily.’5
Arguments against using Split-belt Treadmill Therapy for stroke
The main problem with the split-belt treadmill is that the new gait forced by the treadmill only lasts for a short while. Little research has been done on the long-term effects of the treatment. As one of the researchers, Dr Darcy Reisman, Assistant Professor of Physical Therapy at the University of Delaware, put it in an interview in September 2007,
‘When they come in one time it helps them, but we know that it helps them only temporarily. We need to find out if coming in three or four times a week over several weeks helps them walk better longer.’6
Repeated sessions, however, might prolong the effect. A recent pilot study of 18 people showed that after a single 20-minute session, effects could be seen up to 24 hours after treatment. As the number of sessions increased, the benefits appeared to remain for longer; after 10 sessions, significant improvement could be seen for almost 2 weeks.7 This suggests that using a split-belt treadmill as part of a long-term rehabilitation plan might have long-term benefits. Further research on the long-term benefits of the treatment is needed.
- An article from Science Daily containing a video clip of an interview with Terri Knudsen, a stroke survivor who is testing split-belt treadmill therapy.
- An important early study on the use of split-belt treadmills for improving walking symmetry post-stroke. Focuses on short-term benefits. Reisman DS, Wityk R, Silver K, Bastain AJ. ‘Locomotor adaptation on a split-belt treadmill can improve walking symmetry post-stroke’. In Brain, 2007, vol. 130, p.1861-1872
- A recent study on split-belt treatment focusing more on the long-term benefits. Kahn JH, T Hornby G ‘Gait Symmetry Adaptations Following Unilateral Step Training in Hemiparesis’. In Physical Therapy, 2009, vol. 89, no. 5, p.474-483
Notes and references
- ‘Retrain Your Brain After Stroke: Physical Therapists Use A Split-belt Treadmill To Help Stroke Patients Walk More Easily’. In ScienceDaily, 01-12-2008
- Reisman DS, Bastian AJ, Morton SM. ‘Neurophysiologic and rehabilitation insights from the split-belt and other locomotor adaptation paradigms’. In Physical Therapy, 2010, vol. 90, no. 2, p.187-195, p.193
- Kahn JH, T Hornby G. ‘Gait Symmetry Adaptations Following Unilateral Step Training in Hemiparesis’. In Physical Therapy, 2009, vol. 89, no. 5, p.474-483
- Reisman DS, Wityk R, Silver K, Bastain AJ. ‘Locomotor adaptation on a split-belt treadmill can improve walking symmetry post-stroke’. In Brain, 2007, vol. 130, p.1861-1872
- Reisman DS, Bastian AJ, Morton SM, 2010:187
- ‘Study finds split-belt treadmill helps stroke survivors’ gait’. In UDaily, 25-09-2007
- Kahn JH, T Hornby G, 2009:480-1