Can body weight supported treadmill training cause stepping after complete SCI?

Author: SCIRE Community Team | Reviewers: Tania Lam , Shannon Sproule | Published: 29 November 2017 | Updated: ~

Although we tend to think about walking as being entirely voluntary, the ability to step and walk is actually related to both conscious and unconscious (automatic) processes. Some of the automatic walking processes are thought to be controlled within the spinal cord by networks of nerve cells known as central pattern generators or CPGs.

Central pattern generators (CPGs or spinal pattern generators) are networks of nerve cells in the spinal cord that generate rhythmic movement patterns. These networks do not require signals from the brain or sensation to keep going once they are activated.

CPGs were discovered when researchers found that animals with complete SCI demonstrated stepping movements when they were supported over a treadmill. These animals could not start the movement themselves, but once it was triggered (typically by electrical stimulation, application of certain drugs, or sensory stimulation to an area between the pubic bone and sacrum called the perineum), the stepping movements continued in a rhythmic pattern which resembled walking.

These networks of nerve connections are thought to be located within the spinal cord itself and exist to allow repetitive movements to continue without the need to think about each step.

Generation of rhythmic movement through the CPG is debatable in people with SCI²

Researchers are still unsure about whether central pattern generators can be activated after complete SCI in humans. Researchers have suggested several observations that may show evidence of central pattern generators after complete SCI in humans, including:

• Spontaneous rhythmic movements below the level of injury;
• Stepping-like movements when electrical stimulation is applied through an electrode implanted over the spinal cord (epidural stimulation); and
• Rhythmic muscle contractions that can be induced through treatment with certain drugs.

However, there is debate among researchers about whether these findings really show evidence of central pattern generators or not. It is also not clear if central pattern generators are activated during body weight supported treadmill training after SCI.

Refer to our article on Epidural Stimulation for more information!

It is also important to consider that automatic stepping is not walking. Walking is much more complex, involving many other components, such as strength to support the body weight, balance to stay upright and shift weight, and sensation and voluntary control to adapt to the environment and situation. For these reasons, even if central pattern generators are activated after complete SCI, we do not know whether this will help a person regain walking ability or have any other benefits for functional walking.

Further research is needed to better understand central pattern generators after complete SCI. At this time, body weight supported treadmill training continues to be used clinically as a treatment for people with incomplete SCI who retain some movement in the legs.