The easiest way to relax during a workout, according to fitness experts

In the middle of a recent run, my instructor told the class to unclench our fists. Suddenly I realized that my hands were both actually balled into hard fists, as if I was ready to pick a fight with the treadmill or jump off and start working on my boxing skills.

Supposedly, having unclenched—aka relaxed—hands takes away some of the stress of a workout, leaving you with more energy to do the hard work. When I consciously unfolded my hands, I did feel a subtle, newfound zest to run even faster. After asking some fitness pros, I learned that there is some biological magic that happens when you let go of stress via your hands in a workout.

“Most long distance elite runners—marathoners or ultra marathoners—want to stay loose in the hands to not expend extra energy,” says Emily Kiberd, DC, chiropractic physician and founder of New York’s Urban Wellness Clinic. “Clenching in the fists works its way up the kinetic chain and creates tension in the arms, shoulders, and neck, which can throw a runner’s gait off. The goal for long distance is to not expend any additional energy that doesn’t need to be expended, like clenching your fists.” But even if you’re not a marathon runner, this tip helps in any run that you may be doing.

The thing about a clenched fist is that that tension works its way up and affects more than just your hands. “When people squeeze their fists, that makes its way up into your elbows and shoulders,” says Lara Heimann, physical therapist and yoga pro. “Then you lose the natural rotation that happens when you run—you have a natural rotation of your ribs. But if your shoulders are bunched up because you’re gripping into your fist, that tension’s all over.” (If someone’s doing this, you’ll notice that they definitely don’t look like they’re having a good time running.)

On the other end of the spectrum, having lax hands isn’t so good, either. “If you’re letting your hand just flop down, you can lose energy if it’s open,” says Heimann. So here’s what you should do with your hands instead: Hold your thumb. “I tell people if they’re really used to clenching their fists, put the thumb on the inside of their fingers—then you can’t really squeeze to the same degree,” says Heimann. “You just lightly hold your thumb, and that gives your wrist a neutral position so that it’s not flopping around, but it’s also not clenching.” This is hands down some great advice to have better runs.

Been a while? Here’s how to get back into running if you’ve lost your mojo. And this is how to stretch your calves properly so that ya don’t get hurt.