Going for a run on your own could be bad for your health, according to new research.

Yep, jogging solo could raise your stress levels and interfere with the production of fresh brain cells. In tests on rats, the group which exercised with others showed more than twice as many new brain cells as the group which exercised alone. The scientists believe they’d see similar results in humans and cite their study as evidence that social interactions can buffer the body and brain from stressful experiences.