Here’s How Long It Takes Before Your Muscles Decondition, According to a Sports Medicine Physician

When it comes to your fitness, the use it or lose it principle applies, according to a 2021 review of research published in Frontiers in Sports and Active Living. “With inactivity, people do start to lose measurable muscle strength and [experience] cardiovascular changes within a few days,” says Shane Davis, MD, a Non-Operative Sports Medicine Physician at Tufts Medical Center. But he explains that muscle maintenance and deconditioning are not as black and white as you might think.

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How long does it take to lose muscle?

Most research studying muscle loss and inactivity involves people who are fully immobilized, such as in an intensive care unit (ICU) bed. These studies suggest that people lose three to 10% of their strength per day when on strict bed rest, Dr. Davis says.

He points to one study where doctors fully restrict the leg of an otherwise young, healthy person. “After five days of immobilization, [the patient] lost about three-and-a-half percent of [their quadricep muscle area] and about nine percent of their strength,” he says. “So even with a few days or weeks of strict immobilization, you lose a decent amount of strength.”

This is an extreme example: Most of us aren’t bed-bound in an ICU when we’ve fallen out of our workout routine. Dr. Davis emphasizes that the effect of inactivity on your muscles varies widely based on what this inactivity looks like: Are you sick in bed at home, have your feet up on vacation, just hitting the gym less than usual or have you slipped into a sedentary lifestyle in general? Other factors also play a role, such as your nutrition, sleeping habits, general health, and age.

But ultimately, any substantial decrease in normal activity will result in muscle deconditioning, “and it’ll still show up in those early stages—a few days to a few weeks.”

What are the early signs of deconditioning?

Dr. Davis says muscle deconditioning isn’t going to be particularly noticeable on a day-to-day basis for the average person. This is because even if you’ve missed a few HIIT classes, your body is experiencing a certain level of conditioning just by actively moving around throughout the day.

Dr. Davis points to our hands as an example. “Even if people are sedentary, they still use their hands often.” So, while someone is glued to their couch or desk for a few weeks, they might notice weakness in other body parts. By keeping their hands active while playing on their phone or typing on a computer, they won’t notice much change in those muscles.

Still, while daily movement through activities like cooking and chores can help keep your muscles from losing significant strength, you may start to notice that those groceries feel a bit heavier or you’re losing your breath when going upstairs.

“And when you get back to exercising—or doing what you were doing before—that’s where you’ll most likely notice you aren’t quite as strong as you were before,” Dr. Davis says. It’ll feel harder to do your normal reps, you’ll feel out of breath a little quicker, or your running time might be down. “And that’s normal, expected.”

Can muscle grow back after atrophy?

“You certainly can regain those losses,” Dr. Davis says. But it does take more time for muscle to grow than it does to atrophy. In one study, he says, young, healthy people on strict bed rest lost about three percent of their lean body mass in one week—and it took them 12 weeks to regain it.

Other factors play a role, too. “We lose quite a bit of muscle just as we age, regardless,” so muscle loss due to inactivity can be more drastic the older we get. “Your prior fitness level and general health will matter,” he adds. “More fit, previously well-trained people will maintain better and be able to recover losses quicker than someone who hasn’t previously exercised as much.”

Dr. Davis says that eating a balanced, whole-foods-focused diet also makes a difference in terms of what you might lose—as well as your ability to gain muscle back and make progress in general. In fact, research published in Nutrients says that increased protein intake could be a countermeasure for preserving muscle mass during inactivity.

But whether you’re active or not, you can’t go long without eating enough protein. The current recommended daily allowance (RDA) is a minimum of 0.8 grams per kilogram of body weight just to maintain muscle—and the Nutrients research suggests that eating less than this can have negative effects, including on muscle health.

How to not lose muscle

If you take two weeks off activity entirely, you will lose muscle. But even if you’re going to the gym three times a week, “there are however many hours in the rest of the week—and what you’re doing in that time is arguably more important than the time you put in at the gym, lifting a specific weight.”

That’s why incorporating activity into your daily routine creates a lifestyle that is more resistant to muscle loss for periods when you’re off schedule. “Your legs are already trained, right?” So use them to take the stairs, do some air squats during a quick work break or walk further in the parking lot, Dr. Davis advises. “You’ll still probably have some changes when you’re back at the gym doing weighted squats, but [the muscle loss] will be less so, and quicker to get back into it.”

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