Inflammation, or enlargement, is evidence of tissue damage. Mitochondrial production is a sign of tissue recovery.

The researchers say their findings suggest that massage acts on the cellular level in the same way as many medicines for fighting pain. But these drugs are known to have serious side effects. The researchers believe that massage may be an effective and safer method that could be used as part of normal medical treatment.

A report on the study was published in the journal Science Translational Medicine.

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BOB DOUGHTY: This SCIENCE IN THE NEWS was written Brianna Blake and Christopher Cruise. Our producer was June Simms. I’m Bob Doughty.

BARBARA KLEIN: And I’m Barbara Klein. We have a video about the anniversary of John Glenn’s Earth orbit and planned Mars missions on our website, voaspecialenglish.com. Join us again next week for more news about science in Special English on the Voice of America.