The surprising reason you need to take a rest day

Researchers from Brock University in Canada analyzed blood samples from 15 elite female heavyweight rowers during their most intense training weeks of the pre-Olympic season. Then, they compared those blood samples to ones taken during recovery weeks, which included rest days.

They found that the rowers had significantly lower levels of osteoprotegerin (OPG)—a protein that protects against bone loss—and higher levels of sclerostin (SOST)—a protein that hinders new bone formation—during high volume, high intensity training weeks (an average of 18 hours a week) compared to lower volume training periods.

That’s because training really hard leads to higher levels of inflammation in your body, which may increase your SOST levels, says study coauthor Panagiota Klentrou, Ph.D., professor and associate dean in the department of kinesiology at Brock University.

While there was no difference in the bone mineral density at the end of the study, prolonged high-intensity training may cause damage to your bones over time, Klentrou explains. More research needs to be done to know for sure.

And even though the study looked at female rowers specifically, the findings may be applicable to men as well, says study author Nigel Kurgan, a graduate student in the Centre for Bone and Muscle Health at Brock University.

But Is Your Lifting Wrecking Your Bones?

So while the findings may apply to men too, they really don’t apply to the average gym-goer. In fact, exercise in general is one of the best ways to keep your bones strong, says Klentrou.

But if you’re lifting heavy nearly every day (say, prepping for a powerlifting competition) you might be doing damage to your bones without realizing it.

And that can set you up for trouble down the line: Messing with your bones while you’re young can increase your risk for osteoporosis, making you more susceptible to fractures later on in life.

So Why Should You Take a Rest Day?

Still, even if your training isn’t Olympic-level intense, taking a recovery day comes with its benefits.

If you want your muscles to grow bigger and stronger, giving your body time to bounce back is crucial, says Tony Gentilcore, C.S.C.S., owner of CORE in Brookline, Massachusetts. That’s because when you lift weights, you cause micro tears in your muscle tissues. Taking a rest day gives your muscles time to repair any damage you’ve done.

“Many guys get into the trap that every workout has to be hard, and that’s just not that case,” he explains.

Try alternating the amount of reps you do each week between high, medium, and low volume—keeping the weight the same over each 4-week block of training—so you’re not constantly pushing your body to its limits, says Gentilcore.

You should have at least one day of complete rest a week—or you can shoot for “active recovery,” like going for a walk or doing this quick circuit, which can keep you moving while giving your muscles a break.

How to Deload Properly

And schedule yourself a “deload” week every 4 to 8 weeks to give your body a break so you can come back stronger.

Most people deload naturally—it’s called life, says Gentilcore. Taking vacation, getting sick, or unexpected family events can prevent you from hitting the gym on schedule.

A deload week can be complete rest. But if you can’t stay out of the gym that long, you can deload by cutting your normal volume in half, he says. Consider taking a hiatus that week from the big, compound movements, like deadlifts and squats, since those tend to be most taxing.