The beneficial effects of exercise may be driven, at least partly, by the immune system, new research has shown.

The Harvard Medical School (HMS) study, done in an experimental model, suggested that muscle inflammation caused by exertion mobilises inflammation-countering T cells, or Tregs, which enhance the muscles’ ability to use energy as fuel and improve overall exercise endurance.

The study, published in the journal Science Immunology, may offer a molecular explanation behind this century-old observation.

The immune system, and the T cell arm in particular, has a broad impact on tissue health that goes beyond protection against pathogens and controlling cancer.

“Our study demonstrates that the immune system exerts powerful effects inside the muscle during exercise,” said study senior investigator Diane Mathis, Morton Grove-Rasmussen Professor of Immunology at the Blavatnik Institute at HMS.

Experimental models are not people and the findings remain to be replicated in further studies, the researchers cautioned.

However, the study is an important step toward detailing the cellular and molecular changes that occur during exercise and confer health benefits.

The new findings come amid intensifying efforts to understand the molecular underpinnings of exercises. Untangling the immune system’s involvement in this process is but one aspect of these research efforts.

“We’ve known for a long time that physical exertion causes inflammation, but we don’t fully understand the immune processes involved,” said study first author Kent Langston, a postdoctoral researcher in the Mathis lab.

“Our study shows, at very high resolution, what T cells do at the site where exercise occurs, in the muscle.”

There are efforts afoot to design interventions targeting Tregs in the context of specific immune-mediated diseases.

While immunologic conditions driven by aberrant inflammation require carefully calibrated therapies, exercise is yet another way to counter inflammation, the researchers said.