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It Actually Takes a Lot Longer Than You'd Think to Lose Muscle From Not Working Out

Photograph: Getty Images; Collage: Gabe Conte

If you love to work out, it can be mentally and physically difficult to take time off. I like to strength train four days a week and incorporate cardio by boxing or running, so when I’m too sedentary, my body gets restless, and my focus goes out the window. If I catch a cold or have a jam-packed vacation planned, I feel guilty for allowing my routine to lag for a week or two. But occasionally, dialing down your fitness can be good for you—and unless you really fall out of practice, you’re not going to lose your hard-earned gains.

Just like building your base takes time, so does losing it. We gain strength and endurance by a principle called progressive overload, which involves adding a little bit of intensity to workouts over time as your body adjusts to the original level. “The beauty of progressive overload is we can go back and forth as needed to accommodate as we get stronger,” says Andy Stern, a personal trainer and co-founder of Rumble Boxing. Every day, you can—and should—tailor your workout to your current needs. Super sore or rehabbing an injury? Just lift a little lighter; no big deal.

So, we shouldn’t look at our fitness in a two-week window: “Training is playing a long game,” says Stern. Think about when you were building your base. It might have taken weeks or months to make substantial progress and sometimes even years to notice any change in your body composition. “When you look at the big picture, missing a week or two due to illness and recovery isn't going to set your progress back if you were lifting consistently for months prior,” he says. But how long does it actually take to lose your strength and endurance?

Strength and aerobic capacity respond differently to detraining (disruptions in your training), but in general, you can maintain strength for longer periods of inactivity. According to a 2020 study, three weeks of detraining did not affect muscle thickness, strength, or sports performance in adolescent athletes. According to Jesse Shaw, D.O., associate professor of sports medicine at the University of Western States, this is typical for the general population, too: It usually takes between three and four weeks to start noticing a decrease in strength performance with a complete cessation of activity. “The good news is that unless you are bed-bound or in a weightless environment, like astronauts, activities of daily living and manual labor can prolong the time to notice any significant deficit,” he explains. Given this, the outlook might be even more optimistic: According to a 2022 review, individuals who previously trained their maximum strength maintained their gains even after a 16- to 24-week detraining period.

Aerobic capacity decreases quicker than strength, though, as it “tends to be much more sensitive to periods of reduced training,” says Shaw. Around two weeks off, cardiopulmonary function starts to decrease. You may notice that running or cycling feels much harder than before, and your heart rate is quick to spike.

Overall, the length of time to lose fitness is different for everyone, but the most important factor is how regularly you train. “The more trained you are, the more resistant you are to detraining,” says Shaw. Age is also a factor: A 2005 study found that older seniors (74 to 86 years old) showed a significant decline after two weeks of detraining strength and balance compared to the younger age group (60 to 73 years old), which did not have significant changes.

If you’re really worried about it, Shaw recommends limiting your break from exercise to two weeks or so, when possible. This timeline would “ensure minimal negative changes” and could also be incorporated as a de-load period in your training cycling, allowing for “super-compensation when you return to training,” he says. (This basically means your body will recover enough to perform more effectively upon return than before your break.)

While you’re taking time off to, say, recover from a cold, you can take a few steps to ensure you bounce back as seamlessly as possible. First, eat nourishing food with plenty of protein, which is important to build and maintain muscle mass, says Stern. Protein can “continue to provide a source for muscle building and attempt to blunt muscle breakdown,” says Shaw.

Consider also sprinkling in light movement or even simplifying your current regimen, depending on how you’re feeling. “The easiest answer is [to continue] activities that can replicate your movement patterns at a lower intensity,” says Shaw.

And remember to temper your expectations when you step foot in the gym again. “Your body is like a car and in order to lift well and move weight, the tank needs to be full and the engine needs to be running,” says Stern. If you’re coming back after a period off, you’re probably low on gas. “Your first day back, you may need to modify, but don’t get discouraged,” he says. “Give yourself a few days to re-fuel, hydrate, and simply move. Over time, you’ll feel stronger and faster. Do what you can to prepare for your workout, and then take it one day at a time.”

Originally Appeared on GQ