A pill which could help build muscle without the need for exercise could be more than just a pipe dream following research from Duke University and the University of Texas Southwestern Medical Center in the US which has shown how muscle cells are strengthened by regular exercise.
While this may be good news for couch potatoes everywhere, offering them the chance to earn some of the benefits of exercise without any of the effort they usually involve, the researchers stressed that the principal benefit would be to people with heart diseases or other ailments which prevent them from doing very much exercise.
Dr R. Sanders Williams, dean of the Duke University of School of Medicine, said: "This could lead to drugs that will let people get the health benefits of regular exercise, even if they cannot exercise," thus improving the health of patients with heart or lung disease, or lowering the risk of type 2 diabetes.
But he warned: "It is possible it could become a drug of abuse because it would enhance the performance of athletes."
Williams and his colleagues created a group of mice with genes that over-expressed a signalling protein called calmodulin-dependent protein kinase, or CaMK. When this signalling protein is activated, it and another protein, calcineurin, trigger the physical changes that muscle cells undergo after intense exercise.
Mice with a high level of CaMK expression developed more mitochondria in muscle cells and saw an increase of a type of cell called the 'slow twitch' muscle. These are muscle cells that power sustained activity, such as that required by marathon runners.
The researchers found that mice with high levels of CaMK developed the same healthy muscle cells as mice that did exercise.
Williams said that the effect increased more of the slow twitch muscles, but also raised the number of mitochondria - the structures in cells which metabolise oxygen and thus provide energy - in the fast twitch muscle cells, a similar effect to that which happens in very intense training.
A drug to stimulate the CaMK muscle signalling pathway is still some way off, stressed Williams, but the fact that a specific target has been found should make development a lot easier, the researchers said.