Researchers have developed a virtual reality system that can detect balance impairments.
It's based on a VR system that creates the visual illusion of loss of balance as a participant walks on a treadmill.
The system could help prevent dangerous falls in the elderly by training them to improve their balance while walking.
A virtual reality room at UNC-Chapel Hill's Applied Biomechanics Laboratory. Researchers used a VR system that creates the visual illusion of a loss of balance as a participant walked on a treadmill
Proprioception is an awareness of the position of one's body - the ability to sense stimuli arising within the body regarding position, motion, and equilibrium.
Even in the dark or if a person is blindfolded, he or she knows through proprioception if something is hanging above their heard or next to them.
The sense of proprioception is disturbed in many neurodegenerative disorders, but it can sometimes be improved through the use of sensory integration therapy.
Sensory integration therapy includes special exercises that are used to strengthen the patient's sense of touch (tactile), sense of balance (vestibular), and sense of where the body and its parts are in space (proprioceptive).
The researchers, based at the University of North Carolina at Chapel Hill (UNC) and North Carolina State University (NC State), said the system could be used to detect balance impairments early, and reverse those impairments and prevent falls.
They used the system to perturb participants' sense of balance and record their movements to see how their muscles responded.
'We were able to identify the muscles that orchestrate balance corrections during walking,' said Dr Jason Franz, assistant professor in the joint UNC/NC State department of biomedical engineering.
'We also learned how individual muscles are highly coordinated in preserving walking balance.
'These things provide an important roadmap for detecting balance impairments and the risk of future falls.'
According to the researchers, young and healthy adults rely mostly on the mechanical 'sensors' in their feet and legs to give them an accurate sense of body position.
This is why healthy people don't have much trouble walking in the dark or with their eyes close.
However, this sense of proprioception - an awareness of the position of one's body, declines in the elderly and people who have neurodegenerative diseases such as Parkinson's.
This leads to a much greater reliance on visual cues to maintain balance.
In their study, Dr Franz and his colleagues asked participants to walk on a treadmill in front of a large, curved screen which showed a moving hallway.
'As each person walked, we added lateral oscillations to the video imagery, so that the visual environment made them feel as if they were swaying back and forth, or falling,' Dr Franz said.
Researchers used the virtual reality room at UNC-Chapel Hill's Applied Biomechanics Laboratory to perturb participants' sense of balance and record their movements to see how their muscles responded
'The participants know they aren’t really swaying, but their brains and muscles automatically try to correct their balance anyway.'
The team used 14 cameras to record the positions of 30 reflecting markers on the legs, back and pelvis of each subject, in a setup similar to those seen in Hollywood motion-capture animation studios.
This setup allowed the researchers to see in details how specific muscle groups that control postural sway and foot placement work to correct a perceived loss of balance.
When participants were visually perturbed, they took wider and shorter steps, and their head and torso swayed further sideways with each step.
Electrodes attached to the skin of the subjects also revealed coordinated electrical activity among the muscles that control postural sway and foot placement, including the gluteus medius (on the surface of the pelvis), external oblique (on the abdomen), and erector spinae (a set of muscles that straighten and rotate the back).
The team used 14 cameras to record the positions of 30 reflecting markers on the legs, back and pelvis of each subject, in a setup similar to those seen in Hollywood motion-capture animation studios
'These findings give us important insights into the detailed mechanisms of walking balance control,' Dr Franz said.
The team have ongoing studies in elderly people and plans for studies in people with multiple sclerosis to help develop early-detection procedures for balance problems.
Using the VR system, they were able to identify age-related balance deficits that aren't always apparent during normal walking.
'We think there’s a big opportunity to use visual perturbations in a VR setting to reveal balance impairments that would not be detected in conventional testing or normal walking,' Dr Franz said.
'The key is to challenge balance during walking, to tease out those impairments that exist under the surface.'
The team is also examining the potential of their VR system as a therapy to teach balance-impaired how to improve their balance and avoid falls.
'Early work in our lab suggests it’s possible to use these visual perturbations to train a person’s balance control system to respond better to imbalance that occurs in daily living,' Dr Franz said.
In their study, Dr Franz and his colleagues asked participants to walk on a treadmill in front of a large, curved screen which showed a moving hallway