When it comes to fitness, we’ve all heard the saying Use It or Lose It. While it’s true that when you stop exercising you lose fitness, how quickly you lose it depends on several factors, including how fit you are, how long you have been exercising and how long you stop.

Deconditioning in fit athletes doesn’t appear to happen as quickly or drastically as in beginning exercisers. One study looked at well-conditioned athletes who had been training regularly for a year. They then stopped exercise entirely. After three months, researchers found that the athletes lost about half of their aerobic conditioning.

The outcome is much different for new exercisers. Another study followed new exercisers as they began a training program and then stopped exercise. Researchers had sedentary individuals start a bicycle fitness program for two months. During those eight weeks, the exercisers made dramatic cardiovascular improvements and boosted their aerobic capacity substantially. At eight weeks, they quit exercising for the next two months. They were tested again and were found to have lost all of their aerobic gains and returned to their original fitness levels.

Studies have shown that you can maintain your fitness level even if you need to change or cut back on your exercise for several months. In order to do so, you need to exercise at about 70 percent of your VO2 max at least once per week.

If you stop exercise completely for several months it’s difficult to predict exactly how long it will take you to return to your former fitness level. After a three-month break it’s unlikely that any athlete will return to peak condition in a week

The time it takes to regain fitness appears to depend on your original level of fitness and how long you’ve stopped exercise.