Exercising unaffected limbs helps stroke victims

Cross-education of strength an old scientific notion with a new medical application

VANCOUVER — Stroke victims can make astonishing gains in strength in weakened limbs by training the unaffected limbs on the other side of their body, says new research by the University of Victoria.

Neuroscientist Paul Zehr and PhD candidate Katie Dragert designed “ridiculously simple” devices made of wooden boards and cloth straps that stroke victims used to strengthen the muscles in their legs and ankles.

Patients completed a six-week high-intensity training regime — not with the limbs weakened by the stroke, but with the limbs that were less affected or unaffected.

What happened surprised even the researchers.

Patients gained as much strength in the weakened leg as they did in the leg that did the exercises. Patients achieved strength gains of about 30 per cent in both the trained and untrained legs, a far more dramatic effect than previous research on healthy people had achieved.

The finding promises to be a boon to patients whose limb strength is so impaired by stroke that they can’t lift or train the affected parts at all.

“Weakness is a big part of what happens after a stroke and if you can do something to increase people’s strength, you can help them get walking and all kinds of stuff,” said Zehr.

Much of the training gain in strength and skill that people achieve through exercise takes place in the brain and the nervous system rather than the muscles themselves, Zehr said.

Patients in the study suffered their stroke on average about 80 months before training. That suggests patients can benefit from the program years after a debilitating event.

Zehr and Dragert employed a mostly forgotten 1894 discovery by Yale University researchers who found that when people train one arm, the other arm also gained strength.

Most of the research found that the untrained limb gains about half as much strength as the trained limb.