A retro-style game helped chronic stroke survivors improve arm function by up to 7.8 times more than a sham treatment, a study found.
The home-based rehabilitation programme uses a wearable device to retrain muscles that have become difficult to control independently after a stroke.
Participants completed more than 300 repetitions a day during six weeks of training, with improvements continuing for a month after the therapy ended.
Scientists at Northwestern University developed the 1990s-style video game for people with moderate to severe arm impairment at least six months after a stroke.
The 59 participants had experienced their strokes an average of 6.4 years earlier, while some were 12 years into their recovery.
To play, they wore a small device on their impaired arm and used signals generated by their muscles to control a cursor on a laptop screen.
Tasks included flying a helicopter around the screen to hit a moving target.
The system is called MINT, or myoelectric interface for neurorehabilitation conditioning.
It uses electromyography, known as EMG, to measure the electrical activity produced when muscles contract.
After a stroke, the brain’s movement signals can become disrupted, causing muscles to activate together when they should work separately.
This is known as abnormal co-activation or coupling. For example, the biceps may contract when a person tries to straighten their arm, causing the elbow to bend.
The game identified muscles that were activating together and encouraged participants to control them independently.
Marc Slutzky, professor of neurology and neuroscience at Northwestern University Feinberg School of Medicine and a Northwestern Medicine physician, said: “We have them hit targets that are farther and farther away from that diagonal until they have to separate their muscles and can only hit it by activating one of the muscles and not the other.”
Participants trained for 90 minutes a day, five days a week at home and one day a week in a laboratory, for six weeks.
They were randomly assigned to three experimental groups or a sham control group.
The experimental groups received different forms of training designed to separate the activity of muscles that were moving together.
One group trained two muscles at a time, with the muscles changing every two weeks.
A second group followed the same approach but was also instructed to move its arms as far as possible in the direction linked to the activated muscle.
The third group began with two muscles before adding a third muscle to a three-dimensional version of the game.
The sham group played a simpler game using one muscle at a time and did not receive instructions on separating muscle activity.
Slutzky said: “We wanted to make the sham group as similar as possible, having them do a similar amount of exercise to what the other groups were doing to receive the motivational and exercise factor of these games but not give them the key ingredient, which was the decoupling.”
All four groups improved from the start of the trial to the end of training.
Across the experimental groups, improvements were 4.5 times those recorded in the sham group, which researchers described as clinically meaningful.
The three-muscle group recorded 7.8 times the improvement seen in the sham group at the end of training.
The other two experimental groups did not improve significantly more than the control group when considered individually.
Researchers found that greater reductions in abnormal muscle co-activation were associated with larger improvements in movement.
Slutzky said:“It seems most likely that group three improved the most because they received an extra week of training on the muscles that were causing the most impairment.”
Arm function was assessed using the Wolf Motor Function Test, which measures how quickly people can complete everyday tasks such as lifting an arm to a table, straightening an arm and folding a towel.
Participants receiving the experimental training completed tasks more quickly and improved their range of movement during reaching activities.
Improvements in reaching range were not recorded in the sham group.
The researchers said the approach directly addressed impaired arm movement rather than teaching people to compensate by moving other parts of their bodies.
Slutzky said: “Here we’re doing something different.”
“We’re treating the impairment directly and measuring how much the actual arm improved in addition to performing certain functions. We found our conditioning really caused their improvement.”
Participants were able to complete more than 300 repetitions each day at home.
Slutzky said conventional clinic-based physiotherapy might involve around 30 repetitions on three days a week.
Some participants also reported that the game made rehabilitation more engaging.
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