Have you ever wondered how quickly you lose your fitness level if you stop exercising? This occurred to me recently when I was on safari in Africa for 17 days, and the most exercise I got was standing up in the jeep. Here’s what the science says about maintaining fitness when we take a break from exercise and some tips on what to do about it.

Aerobic Fitness Is The First To Go

Aerobic fitness begins to diminish relatively quickly after we stop exercising. The timeline for this decrease can vary depending on several factors, including our baseline fitness level, the intensity and duration of our previous training, and our overall health.

Within a few days to a week, there is a drop in our blood plasma volume.
After two weeks with no aerobic activity, there is a noticeable decline in VO2 max (the maximum amount of oxygen your body can use during intense exercise, which is a good measure of cardiovascular fitness).
After a month, there is a significant reduction in VO2 max, possibly by as much as 10-15%, and after two months, this loss can be 20-25%

Per Dr. Abbi Lane, an assistant professor of Applied Exercise Science at the University of Michigan School of Kinesiology, “With aerobic fitness, if you don’t train for months, you lose it, and it is like starting over almost every time.”

Muscle Mass Declines, But Not As Fast

Muscle mass declines more slowly, based on your previous training level, diet, age, and overall activity levels.

Within a week, there is no noticeable decline in muscle mass
Within 2-3 weeks, there are initial signs of muscle atrophy (shrinking of muscle fibers).
After a month, there is a noticeable decrease in muscle mass and strength and a reduction in neuromuscular efficiency (your nervous system's ability to activate muscles).

Wait, There is Some Good News!

The good news is this: maintaining any activity level will help counteract these declines. You don’t need to attend a formal exercise class. Going upstairs, doing yard work, and taking your dog for a walk all count. The key is to use your muscles in a way that works for you. This can be more challenging if you have an injury or just had surgery. In this case, ask your doctor to recommend a physical therapist who can get you started on the right path, which typically includes some type of movement, even if is not the same or as intense as what you used to do.