How Fast is Muscle Lost When Not Training?

The minute you stop training, your body stops building muscles. How rapidly your muscle strength and overall fitness decline depends on a number of factors. One thing is for sure: You'll lose your muscles in a shorter amount of time than it took to build them. Even if you can't maintain your regular training, there are ways to help halt the process.

Close-up of a woman lifting weights. (Image: Paul Burns/Blend Images/Getty Images)

Process

Detraining is the technical term for muscle loss following a stop in training. Your body, which was used to the regular workouts that helped build up muscle, is suddenly left without them. During regular training, your body increased its production of enzymes that help build your muscles and keep them strong. When you stop training, your body no longer produces the extra muscle-maintaining enzymes and your muscles react with atrophy.

Factors

Your overall fitness level and how long you've been working out are two major factors that determine how quickly and severely your muscles will atrophy during detraining. Your muscles will take longer to atrophy if you are in a good shape and have been training for an extended period, such as one year or more. You will also retain a higher fitness level during detraining than you would if you are new to exercise. If you've only worked out for a month or two, Columbia University says, your muscles will atrophy much quicker and your fitness level can drop as low as it was before you began.

Time Frame

In the most drastic scenario, you can lose up to 80 percent of your fitness level in as few as two weeks if you're new to exercise. If you are incredibly fit and have been training for years, you'll hang onto your fitness level for about three months, ACE Fitness says. If you start retraining after a lull, however, your muscles will remember where you left off and build up more rapidly than if you were just starting a new program. The detraining period actually strengthens muscle fibers, which means your retraining can lead to a higher fitness level that you might have been able to achieve had you not taken a break, Columbia University says.

What You Can Do

Just because you have to stop your training doesn't mean you have to stop being active. Even if you can't follow the same workout regimen your body is used to, you can still slow down or even stop the detraining process if you engage in other activities, ACE Fitness says. If you're recovering from an injury that prevents training, you might still be able to work out in a pool, for instance. If you can no longer run, walking at least can help keep your fitness level higher than inactivity would.