Sheer grit and determination allowed one child to overcome his inherited muscle weakness disorder. Greg Cremen, 45, who suffers from nemaline myopathy, is now a competitive cyclist.

"My father always taught me that my condition was a challenge and that I should not give up pushing myself even further," says Greg.

By exercising Greg has been able to make his muscle fibres grow larger and therefore stronger, effectively treating himself and reducing his weakness.

Now a muscly mouse has shown Dr. Edna Hardeman, Head of CMRI’s Muscle Development Unit and  Professor Kathryn North of the INMR a way to help many children benefit from this simple natural approach.

Nemaline myopathy is a recessive genetic disorder in which children inherit a faulty muscle protein gene from both parents. The disease causes generalised muscle weakness and the severity of the disease varies in different children. In extreme cases the muscles that control breathing are affected and the child dies of respiratory failure soon after birth.

"In the past we have questioned whether exercise might be too much for the muscle to handle, but Greg has demonstrated that this is not the case," says Dr. Hardeman.

Using a mouse model of nemaline myopathy, Drs Hardeman and North have shown that mice, like Greg, are able to effectively cure themselves of the disease by increasing the size of their muscle fibres. This phenomenon, called hypertrophy, occurs in humans when they exercise, so increasing their muscle strength. But in humans the effects of exercise can differ and some children with nemaline myopathy are too weak to exercise.

Using clues from people like Greg and the mice, Dr. Hardeman and Associate Professor North believe they have found the key to produce an effective treatment. The disease only becomes a problem in the mice when they age and their muscles begin to shrink.

By exercising the mice on motorised treadmills they hope to confirm the beneficial role of exercise and hold off this age related muscle atrophy.

They will also try to mimic this effect with a number of pharmacological agents.

A promising candidate drug is a natural growth factor involved in muscle development, called Insulin-like Growth Factor I. Dr. Hardeman is also testing other hypertrophy promoting compounds, which are the subject of a patent application, in collaboration with Emory University in the United States.

"Depending on the results that we achieve with the mice, we hope to be able to use these treatments on children with nemaline myopathy," said Dr. Hardeman.

This article was originally published in Under the Microscope: The Newsletter of the Children’s Medical Research Institute, May 2001.