Conventional wisdom tells us that exercising helps relieve stress. But for people who are less athletically inclined, the idea of going to the gym is more likely to make them break out in a cold sweat.

So what if there were a way to get results without having to log time on a treadmill? That’s the question that the BBC Two series Trust Me, I’m a Doctor sought to answer in a recent episode.

The episode featured an experiment examining a technique called motor imagery conducted by Professor Tony Kay from the University of Northampton. Kay measured the strength of the participants’ calf muscles by testing how hard they could push against a surface outfitted with sensors. Then, he used an ultrasound to record muscle size.

Related: This Cute, Little Robot Wants to Be Your Personal Health Buddy

The volunteers were asked to set aside 15 minutes each day to think about the exercise that they did under Kay’s watch. When they performed the test again a month later, the participants’ muscles were an average of 8 percent stronger. How did that happen?

Kay told host Michael Mosley that because the volunteers were thinking so intently about the muscle movement, when it came time to try the exercises again, “they got better at recruiting the muscles in an orderly fashion so they could activate a larger percentage of the muscle. That produced more force and so they became stronger.” Kay also recommended this visualization strategy for folks who are injured and working toward getting their strength back.

Related: Want to Inspire Your Employees? Get Some Sleep.

And this isn’t the only evidence of the brain’s role in developing strength. A 2014 study published in the Journal of Neurophysiology found that mental imagery training helped those with weakened wrist muscles gain back more of their strength compared to those who did not use the technique.

It seems that you shouldn’t underestimate the mind-body connection.