Consider this your permission to skip the gym today: Exercising too much without giving your body a break might make you sick, according to new research published in the journal Frontiers of Physiology. Researchers at Catholic University of Brasilia observed people who do CrossFit on a regular basis to see how the high-intensity exercise affected their muscles and immune system. After two consecutive days of the rigorous workout, people showed reduced levels of anti-inflammatory cytokines—proteins that white blood cells produce to help lower inflammation. In effect, the back-to-back workouts with no rest were hampering their immune function.

That study looked at CrossFitters specifically, but they’re not the only ones who need a little R&R. Taking some time off from the gym is essential, no matter what kind of workout you tend to do—whether it’s weight-lifting or running or something low-impact like a barre class. “Rest days are important regardless of intensity level because you’re placing the body and mind under some form of stress,” says Marlon Briscoe, a certified personal trainer and owner of BodyByBriscoe Studios in New York City. “Imagine going to school or work 365 days a year with no break—how would you feel?”

Keep reading for his tips about how to make the most of your days off.

1. TAKE OFF AT LEAST ONE DAY A WEEK.

If you’ve been exercising regularly for a while and are fairly advanced, you can probably get away with working out three or four consecutive days without any time off, says Briscoe; but even so, make sure to take off at least one full day each week. If you’re a newbie, you might want to ease into a routine and give yourself another day or two off (spread them out throughout the week).

“When you have a day or two off between workouts, your body will be able to come back at full force,” says Briscoe. Plus, he says, your mind will be rested, “so you’ll also be more encouraged to continue your program.”

2. ON WORKOUT DAYS, MIX IT UP.

If you do work out a few days in a row, make sure to target different muscles—for instance, do arms one day and legs the next, or alternate running days with cross-training. “Muscles break down during exercise and repair when you’re at rest,” says Briscoe. So if you keep working the same muscles over and over, they don’t get the chance to build themselves back up. “You’ll compromise your results if you work out the same body parts on consecutive days,” he says.

Another reason to change up the routine: You’ll lower your chances of injury. If your muscles are tight or sore and you try to work through the pain, you have a great chance of harming yourself, says Briscoe.

3. ON YOUR OFF DAYS, BE LAZY.

Don’t be tempted to go for an easy bike ride, jog, or yoga class on your day off—because you won’t really be giving your body the break it needs. “A rest day should be just that: rest,” says Briscoe.

If you want to do something a little active, he advises sticking to easy stretching (holding each stretch for at least 30 seconds) or foam rolling. Those will help keep your muscles loose without putting too much added strain on them.

4. PAY ATTENTION TO THE P.M.

Getting enough Zs is another key component to your recovery post-workout, says Briscoe. He also recommends eating something with casein protein before you head to bed to help your muscles further recover while you sleep. Science has shown this is a good strategy; in fact, downing a beverage with casein protein half an hour before bedtime improved exercisers’ protein synthesis rates (which helps repair muscles) by 22 percent in a 2012 study published in Medicine & Science in Sports & Exercise. So feel free to enjoy a protein shake as a midnight snack.