How Fast Do You Lose Muscle Definition?

Whether you exercise to lose weight, build muscle, or improve your overall health, strength training probably comes into play at some point. Strength training is a type of exercise focused on increasing the strength and size of your skeletal muscles as well as anaerobic endurance through increasing resistance to muscular contractions (via Better Health). Put more simply, it's any exercise where you try to contract your muscles (say by bending your arm in a curl) while a weight attempts to resist the contraction (for example, a hand weight).

Unfortunately, this hard-earned result isn't permanent. In a very real sense, strength training provides "use it or lose it" results. As Dr. Alyssa Olenick told Shape, "losing muscle" means losing both muscle size as well as some of your muscular strength. Dr. Olenick went on to explain that losing muscle can also mean losing some connectivity in your neuromuscular system, which is defined by Healthdirect Australia as the system of nerves that connects the thoughts in your brain to the movement in your muscles.

Each of these attributes goes into what most people think of simply as their strength. And, as "use it or lose it" implies, these benefits diminish if you take too much time off from training. But just how much time is too much?

During her Shape interview, Dr. Olenick gave a fairly specific timeline for muscle loss. She stated that you can entirely skip a week of training — maybe even two — before you see any real muscle loss. You will see some, she cautioned, but the difference will be minute. Even then, Dr. Olenick explains that the loss isn't actually muscle. It's a reduction of fluid and carbohydrates in the muscle tissue.

You may be tempted to measure your muscles before you jump back into training to determine how much you've lost. A better measurement of muscle loss, Olenick says, is to repeat part of your usual workout to determine if it feels more challenging than it used to. If you can't feel a difference then the loss isn't a problem. But if the exercise feels more challenging, then you've lost a notable amount of your strength.

That's no reason to avoid your weight training, however. As a 2018 study published in Scientific Reports found, your body has an epigenetic memory of the fitness gains you've achieved in the past. This means that your body will react more quickly to your workout routine when you dive back into it, bringing you back to your former strength in a shorter time frame than it took you to initially achieve it.