Have you ever walked or ran on a treadmill? If we ask this question to a person, the answer will probably be ‘yes’. But, have you ever walked on a split-belt treadmill? Do you even know that this kind of treadmill exists? This is a relative new equipment that researchers started to use a few years ago with the objective to investigate the process involved in the control of the independent movement and combined movement of our legs. The researchers are interested in explore how the brain sends a message to the legs to perform a movement and investigate how this message is send separate to one leg separate or to both legs. These recent studies demonstrate a great potential for the use of the split-belt treadmill in the rehabilitation process of people who had some kind of neurological or orthopedic impairments in their walking.
The split-belt treadmill seems like any other regular treadmill, but it has two separate belts alongside each other. Each belt controls the movement of one of the legs independently. It is possible to move the two belts at the same speed or in different speeds. Even more impressive the belts can move not only in the forward and backward direction, but also each belt can move in different directions at the same time. There are many companies in the market that sell this type of treadmill. Depending in the amount of other features combined to the split-belt treadmill, such as a force platform, the price may range from US$ 2,000 to US$ 20,000. This can be an expensive investment, that is one of the reasons why this type of treadmill is used more often in research labs. We might also see it use in gym, but its use is not so specific as for research.
Specifically, for research, the split-belt treadmill has been shown to be and innovative and versatile tool. The kind of manipulation of the leg’s movement described before allow the researchers to see in a real situation how the brain responds to an unusual walking situation. This is particularly important for the walking rehabilitation, because every day while walking we need to change speed or directions to avoid an obstacle or to perform a daily activity. Imagine when you have an injury, this simple daily tasks can be even more challenging. Before, we can apply the split-belt treadmill as a rehabilitation tool it is essential to determine whether the movements learned while training in the split-belt treadmill can be transfer to daily activities.
For this reason, researchers need to know how our brain acts in challenging walking situations. During walking in the split-belt treadmill, when the leg move at independent speeds or direction, causes our brain to receive an error signal. This message will be processed by the brain and some other structures of our nervous system and will be used to send a new signal for our legs to try to adjust our walking pattern. In order to adapt to this new situation, our legs tend to perform an independent step length in each leg. This response of the nervous system is stored and will be used when we are exposed again to a similar challenging walking situation. In other words, the nervous system will recall this message every time that we are exposed to this context.
But how to we transmit these findings in benefit of the patients? First, it is necessary to differentiate the clinical populations which be benefited by these findings. For example, an athlete with a ligament knee rupture or an ankle sprain, can lead to walking asymmetries. Moreover, patients who had a stroke, due to injuries in their brain have also walking impairments. These patients have different primarily causes for their gait impairments, but therapists can use the same tool to rehabilitate these patients. In clinical practice, during the rehabilitation the split-belt treadmill is used to stimulate our brain to adapt faster and efficiently. This type of rehabilitation has been proven that the directed stimulus induces the nervous system to naturally adapts and modifies the walking pattern. It is important that the therapist during the performance of the training stimulate the repetition of the training and instruct the patient to reinforce the learning. Before any intervention in order to promote a successfully rehabilitation, the therapist will need to do a careful evaluation measuring the asymmetries between the two legs. Only knowing the benefits and how to program the split-belt treadmill, this will be an effective rehabilitation tool.
Ft. Gabriela Borin