Can the health of one part of the body be improved by exercising a different part? Unlikely as it may seem, the idea is gaining traction among scientists looking for new ways to manage the effects of chronic diseases, strokes and even breast cancer surgery.
Now, researchers at the University of Texas at El Paso are about to test a surprising new theory that people with osteoarthritis can eliminate knee pain by exercising their arms.
Last week, researchers launched a new clinical trial in which 60 men and women who experience frequent pain as a result of wear and tear on their knees will try different exercises to see which gives them the most relief.
The trial, which will end in 2025, will test whether regular 20-minute arm exercise sessions (using an “arm cycle” machine like those found in gyms) is better than leg cycling for relieving leg pain. knee and increase mobility.
The goal is to try to replicate the findings of previous small studies that suggested that cycling with your arms is better than walking on a treadmill for relieving knee pain.
Researchers have launched a new clinical trial in which 60 men and women who experience frequent pain as a result of wear and tear on their knees will try different exercises to see which provides the most relief (file image)
Regular, moderate exercise is one of the best ways to manage arthritic knee pain, as it strengthens the muscles around the joint and relieves pressure on the damaged area.
But walking or jogging can increase the load on the knee, making it difficult for some people to move. “There is no obvious mechanism by which arm exercise can relieve knee pain,” says Uzo Ehiogu, a physiotherapist at the Royal Orthopedic Hospital, Birmingham, commenting on this approach.
“What is probably happening is that patients feel fitter and more confident, and may be more mobile, after a 20-minute arm workout, which may then reduce the sensation of pain in their knees.”
But in some cases, exercising one limb actually has a direct and fascinating impact on the opposite one.
Recent evidence of this appeared in a study published in July in the Scandinavian Journal of Medicine and Science in Sports.
Researchers at National Taiwan Normal University in Taipei, Taiwan, recruited 30 volunteers who held one arm completely still for hours at a time while flexing the muscles of their free arm; others kept both arms still.
After several weeks, those who contracted the muscles in their moving arm lost only 2 percent of the muscle in their immobile arm.
However, in the non-exercise group, muscle wasting in the static arm was 28 percent.
This effect is known as muscle cross-training, where muscles on one side of the body benefit from the activity of those on the other side. It is commonly used in sports medicine to reduce the rapid loss of muscle mass during an injury.
Studies show that a sling-injured arm loses up to 60 percent of its muscle strength in the first five weeks. “But with regular exercise of the other limb (‘contralateral’ training) the muscle wasting will be greatly reduced,” says Mr Ehiogu.
It is not clear exactly how muscle cross-education works. One theory is that this is a “trickle-down” effect, whereby exhaustively exercising the healthy limb (lifting weights with one arm or doing squats with one leg, for example) also generates new connections between the brain and the injured limb.
After several weeks, those who contracted the muscles in their moving arm lost only 2 percent of the muscle in their immobile arm (file image)
But the key to its success, says Mr Ehiogu, spokesman for the Chartered Society of Physiotherapy, is to work the good limb harder than normal by increasing resistance, that is, lifting a heavier weight.
“You need to work between 80 and 85 percent of your maximum capacity,” he says. ‘So if you normally do ten reps working at 50 percent of your max, try doing five reps, but at 80 or 85 percent of your capacity.
“If you don’t increase the resistance, you don’t get the crossover effect.”
One of the most intriguing examples of this phenomenon is mirror therapy, used in stroke patients who become paralyzed on one side.
His damaged arm is placed inside a box with a mirror on the outside; The patient then does a series of exercises with the healthy arm to improve strength and grip, while looking at the same arm in the mirror.
This “tricks” the brain into believing that the damaged arm is working, activating connections with its nerves and muscle fibers.
Walking or jogging can increase the load on the knee, making it difficult for some people to move (file image)
A 2018 review of mirror therapy in stroke care by Cochrane (which reviews evidence for medical treatments) concluded that it improved movement in paralyzed limbs enough for patients to perform daily activities such as cleaning.
And a study published in June in the Journal of Cancer Survivorship, conducted by Fudan University in China, found that mirror therapy also helps women with limited shoulder function after surgery or radiation therapy for breast cancer.
Both treatments can cause immobility and pain as a result of tissue removal, nerve damage, and scarring. In the study, half of the 79 participants exercised their unaffected arm daily while looking in a mirror; the rest did the same without a mirror.
After eight weeks, the mirror group had better range of motion in the affected arm than their peers. In a report on the findings, the researchers said: “Breast cancer survivors can try mirror therapy for effective shoulder rehabilitation.”