How Quickly Do You Lose Muscle if You Stop Lifting Weights?

Is an upcoming vacation sparking anxiety about your focus on building muscle? You'll be happy to learn that although your muscles may shrink a bit, your strength will likely stay consistent — and your body should bounce back quickly when you return to your fitness routine.

You can start to lose muscle quickly after quitting the gym, but the good news is you can also build it back — and fast. (Image: Getty Images/Westend61)

Here's what you need to know about building and losing muscle to enjoy your vacation with confidence.

Why Your Body Builds Muscle

There are two types of muscles in the human body: slow-twitch (or type 1) and fast-twitch (or type 2), according to the National Academy of Sports Medicine (NASM). While fast-twitch muscles are responsible for producing greater force, they fatigue quickly. On the other hand, slow-twitch muscles don't produce as much power but are able to maintain longer-term contractions. Working both types results in gains in size and strength.

Hypertrophy, according to the NASM, is the growth of muscle fibers in response to high volumes of tension, and that tension occurs when you lift weights. Over time, as you add more resistance or weight to your exercises, your body meets you halfway, increasing muscular strength and size. This is why gradually progressing at the gym results in muscle gain.

Atrophy, on the other hand, is the loss of muscle, according to the U.S. National Library of Medicine. Typically, this is caused by lack of use over time. When atrophy occurs, according to the NASM, your muscles shrink in size and your strength decreases.

Losing Muscle Doesn't Always Mean Losing Strength

There's no hard and fast timeline when it comes to muscle loss. The rate of muscular atrophy depends on your starting point, according to the NASM. If you're an experienced weight lifter or athlete, it will take longer for your body to lose muscle. However, strength and muscle mass aren't the same thing. While visible size can decrease quickly, the body can retain strength for much longer.

The average person starts to lose muscle mass after a week of inactivity, according to an October 2016 study conducted by the American Diabetes Association. However, this may be due to a reduction of energy stores (glycogen) in the muscle caused by skipping your workouts. (After you exercise, your body increases glycogen synthesis in order to replenish tired muscles, according to Harvard Health Publishing, which also gives the appearance of larger muscles.)

Muscular strength, however, has a different timeline of deterioration. According to a 2018 study published in Frontiers in Physiology, a six-week hiatus after 11 weeks of consistent training resulted in decreases in thigh circumference and muscle thickness. However, this period of rest did not affect a measure of muscular strength called maximum voluntary contraction torque. In other words, while the subjects' muscles visibly shrunk, their strength did not.

Strategically Reigning In Your Training

Back to that vacation that's on your mind: The good news is you won't need to spend much time in the gym. Just one session per week is sufficient to maintain initial strength over eight weeks, according to a March 2017 study published in the European Journal of Sport Science. The study also measured the size of participants' quads and found they were able to maintain the size of their muscles over the study period with as little as one training session per week, too.

Keep in mind that all bodies are different. Genetics also play a roll in muscle growth, not to mention the body's ability to maintain that development. You might find you need two training sessions a week to maintain your muscle size and strength, for example.

Bouncing Back After Time Off

Your muscles have their own way of storing information, much like your memory. Even after you've stopped working out, your body is capable of "remembering" prior hypertrophy, and you'll regain muscle mass more quickly after it's lost, according to a January 2016 review published in the Journal of Experimental Biology.

If you're going back to the gym after a long break, start slowly, Harvard Health Publishing recommends. In this re-introductory period, ease into exercise and listen to your body, adjusting your resistance accordingly. Stick to low-intensity workouts and build up gradually, taking appropriate time to recover between gym sessions.

Alongside a gradual reintroduction of exercise, up your protein intake to combat muscle atrophy. According to a 2018 study published in the American Journal of Clinical Nutrition, consuming roughly 1.5 grams of protein per kilogram of body weight should be sufficient to fight off deterioration.

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