Scientists in the 19th century were already on to something that can help stroke patients today. In a study from 1894, a woman who trained her right hand saw an increase in strength in her left as well. This finding sparked the interest of scientists and many studies followed.
Learning more about a strange phenomenon
Is it true that training one side can help the other side too? It is. You might have heard about this phenomenon either as cross-education, cross-training, or interlimb transfer. And research shows that this can be an effective training method with measurable outcomes.
But the question remains. How can training one side of the body increase the strength on the other side of the body? How it works is not yet entirely clear. But scientists believe it is most likely a combined effect of an increased neural drive (the amount the nervous system is activated) and muscular adaptation. So when you exercise, your neural drive increases. And when you train just one side, the nervous system automatically activates the neurons of the other side as well. This activation increases the amount of information sent to the muscles on both sides of the body.
How much does this really help?
At first, scientists studied interlimb transfer in healthy individuals. The results showed that the untrained arm increased as much as 50% of the trained arm. Because it was so effective, researchers imagined it could offer stroke patients a chance to increase the strength of their affected side by training their healthy side. So they put it to the test.
They learned that this method is, in fact, useful for stroke survivors. One study reported that a 5-week training program of the lower arm of the unaffected side increased strength in the trained side 42% and of the affected side 35%. This news is encouraging because it means that even when one side is severely affected, there is a chance to improve.
We must note here that this method is useful for strength increase, but probably not for improving functional performance. And the question remains as to how much you should train to really benefit from the increased strength in daily activities. However, getting stronger can set a good foundation for other forms of training.
Strokemark putting this knowledge into action
At Strokemark, we incorporate this valuable knowledge in our training programs. And we aim to find out what the optimal amount of training is by tracking the progress of every individual user.
The Strokemark team would also like to offer one very important tip! If you want to train the strength of your affected side, perform the exercise first with your healthy side, directly followed by your affected side. Let us know if you feel a difference in your training!
The lead authors of these studies are:
- Rafel Cirer-Sastre from the National Institute of Physical Education of Catalonia (INEFC), University of Lleida, Lleida, Spain.
- J. Fariñas from the Department of Physical Education and Sport, Faculty of Sports Sciences and Physical Education, University of A Coruna, Performance and Health Group, A Coruña, Spain.
- Y. Sun from the Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, BC, V8P5C2, Canada.
- T.J. Carroll from the Health and Exercise Science, School of Medical Sciences, University of New South Wales, Sydney, Australia.