In some studies, massage therapy has been shown to increase white blood-cell count. In a new study, European scientists have found that, when a muscle is injured, white blood cells called macrophages play a crucial role in its regeneration.

The findings were published online in the journal Proceedings of the National Academy of Sciences.

The scientists from the European Molecular Biology Laboratory also uncovered the genetic switch that controls this process, a finding that opens the door for new therapeutic approaches not only to sports injuries but also to diseases such as Duchenne muscular dystrophy, according to a press release from the laboratory.

Normally, macrophages—the white blood cells known for engulfing and eliminating bacteria and other infectious agents—are drawn to areas of injury. Once there, they act as “garbage men,” eliminating the dead cells and releasing pro-inflammatory factors, fending off infection.

After clearing up the debris, macrophages stop releasing those pro-inflammatory factors, and start making anti-inflammatory factors that promote repair in the damaged area. This shift from clearing debris to promoting building is known as macrophage polarization and is essential for muscles to regenerate properly.

“There seems to be this point of no return”, says researcher Nadia Rosenthal. “If macrophages don’t make this switch, then the muscle won’t repair itself [and] you just end up with scar, instead of new tissue.”