Anyone who trains regularly knows that the results of physical activity are very difficult to build and very easy to lose. Whether you’re too busy, injured, or your plans have changed, you’ve probably wondered more than once whether—and how quickly—you’ll lose the strength, speed, or endurance you worked so hard to develop.
Let’s start from the end: The answer to this question is, of course, complex and depends on several factors—the length of the break, what you do during that time, your age, your current fitness level, and yes, genetics as well. But recent studies provide a fairly clear picture of what happens to the body when it doesn’t get its regular workouts—from a few days to long months of rest.
After a few days: No problem at all
First, some good news: When examining improvement in cardiovascular endurance and muscle strength, a few days off don’t really affect the results, whether you’re on vacation abroad, dealing with an illness, or recovering from an injury. Moreover, studies show that a rest period of three or four days can actually be beneficial, as it gives the body time to recover and strengthen following the last workout—especially if it was more challenging than usual.
After two weeks: Endurance starts to decline
As your break extends, it will likely affect endurance first, before showing in physical strength or muscle mass. Most of this effect will appear in the VO2 max—the amount of oxygen your body can absorb during physical activity. As this number drops, activities like running and cycling will start to feel more challenging and tiring.
A 2024 meta-analysis found that in trained athletes, VO2 max is expected to decrease by about 7 percent after a 12-day break from training. During a two-week break, you’re unlikely to see any drop in muscle mass, although you may feel some stiffness or muscle soreness when you resume training.
After a month: Endurance continues to drop, but muscles hold up
The same 2024 meta-analysis found that even after five weeks, VO2 max is expected to drop by another 10 percent. This decrease continues as more time passes—13 percent after six weeks and 20 percent after about two months. The lowest point occurs at week 12, after which no further decline is expected and the value stabilizes. During this time, it’s still unlikely you’ll notice a significant loss of physical strength or muscle mass, though complete inactivity may cause joint stiffness.
After a few months: The body “remembers” the workouts
From the second month onward, a gradual decrease in strength and muscle mass is expected—but again, there’s good news. A 2024 study found that if you trained consistently for a long time, you’re much more likely to regain your strength and muscle mass faster after a break from exercise.
In the study, men and women with limited strength-training experience participated in a ten-week resistance training program, took a ten-week break, and then returned to the original program for another ten weeks. Findings showed that participants regained their physical strength and muscle mass quickly during the final phase—certainly compared to their first round of training. The researchers noted that if you previously trained consistently, you don’t need to “worry too much about short-term breaks.”
A 2022 meta-analysis reviewing multiple studies on the subject reached a similar conclusion, determining that for people who train regularly, improvements in strength and muscle mass do not completely disappear after periods without training—and often remain higher than before starting workouts.
Common mistakes that harm you during breaks
It might seem logical, even necessary, to change your diet when you stop training, since you’re not burning as many calories—but a calorie deficit can actually worsen muscle loss and make it harder to bounce back when you resume exercise. To avoid this, it’s best to maintain your usual protein intake from your training period even during your break.
And when you do return to working out, don’t go all in at once. Workouts that once felt easy may now feel more demanding and leave you sore, stiff, and fatigued. Give yourself time to ease back in—spend more time on warm-ups and progress slowly, using lighter weights than you were used to before.