Scientists have isolated a previously unknown protein in muscles, which spurs their growth and power following resistance exercise.

They suggest that artificially raising levels of the protein, PGC-1 alpha-4, could have long term benefits in reducing muscle wastage, particularly in cancer sufferers and those who undergo prolonged inactivity, such as hospital patients.

Mice given extra doses of the protein gained muscle mass and strength and rodents with cancer were less affected by muscle loss. They were also stronger and more resistant to fatigue.

Bruce Spiegelman led the team at the Dana-Farber Cancer Institute. He said that resistance exercise, such as weight lifting, causes a rise in the protein, which trigger bio-chemical changes to make muscles larger and more powerful.

Researchers found that the new protein conrols the activity of two previously known molecular pathways involved in muscle growth. A rise in PGC-1 alpha 4 with exercises increases activity of a protein called IGF1, which facilitates muscle growth. At the same time PGC-1 alpha 4 respresses another protein, myostatin, which normally restricts muscle growth. In effect, PGC-1 alpha-4 presses the accelerator and removes the brake to enable exercised muscles to gain mass and strength.