Split belt treadmills were originally designed to help stroke victims learn to walk again. They were introduced as part of the rehab process after researchers discovered that the body contained separate nerve networks directing the movements of each leg. There is another device researchers are using to study and improve the human gait and that's called the force sensing treadmill. Let's take a quick look at each:
Split Belt (Side-by-Side)
Scientists have found that our legs can be taught to function almost independently of each other. This discovery has lead to putting test subjects on split belt treadmills in which one side of the belt moves at a different speed than the other. Or, one side can move one foot back while the other moves forward. Using this machine, stroke patients, and others with incomplete spinal cord or brain injuries are having their brains "re-wire" themselves to mimic normal leg control.
Decades ago, doctors thought that the brain could not learn again once function was lost. Yet recent research has proven that the brain has the ability to acquire new skills and knowledge through repetition and instruction. Doctors have now learned that the right circuitry for walking still may exist in the damaged brains of many patients. This dormant system can be challenged by movements of the legs on the split belt treadmills to reawaken the old gait.
How it works: Your brain constantly and automatically tries to adjust your skeletal structure to keep you upright. The ability to teach the brain to learn through repeating motor skills is the phenomena known as neuroplasticity. In this case, it's related to reorganizing neuro pathways to achieve lower body movement. The central nervous system is retrained to adopt walking motions - at least during the time spent on the treadmill and for a short time afterward.
Treadmills have long been used in therapy and conditioning of rehab patients. Relearning coordination as a result of a few sessions with these split belt treadmills are at the heart of the methodology. Patients work on leg muscle development and range of motion, swing phase duration of the leg and foot clearance.
Force Sensing Treadmill (One Belt in Front of Another)
Another innovative design is the force sensing treadmill which is used in scientific studies as a gait analysis system to measure the force of footfalls separately and accurately. Developed for the U.S. Army at its Research Institute of Environmental Medicine, researchers can determine the pressure each foot is exerting while walking or running.
The Force Sensing Treadmill, built by Advanced Mechanical Technology Inc. of Watertown, Mass., positions two belts on the front and back of the deck rather than side by side. Again, it resembles a regular treadmill but if you look closely it has a break between the two belts. Each force platform is attached to a common chassis. The belts move around their perspective rollers at the same speed while sensors collect data when each foot strikes the belt during a walk or run. Like a regular treadmill, speeds up to 11 mph are possible and it even has an incline ramp up to 25 percent.
Now that the torque of the footfalls can be measured and analyzed separately, researchers are able to study the gait biomechanics. The subject walks normally on the belts and would feel no difference from walking on a regular treadmill. The force sensing treadmill then records 3-D forces and torques on each foot during the durations when either foot is in contact with the belt. Since both feet never strike the same belt at the same time, the force strike can be measured more accurately. Thousands of data points per second are recorded by the platform as well as video cameras for analysis.
The split belt treadmills and the specialized force sensing treadmill are at the forefront of biomechanical technology. Relearning coordination and advancing locomotor skills are just the beginning of what these researchers hope to achieve with these machines.
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