You will probably keep your muscle mass if you don’t workout for a week. But there are exceptions. This is what science has to say.
What Happens When You Don’t Workout for a Week
Let's say you've skipped gym sessions for a week, and you notice something startling in the mirror: you look smaller.
Your immediate thought might be, "Am I losing muscle?"
The answer is: No. Taking a gym break for a week can be a good thing.
You look smaller because of water loss
When you miss workouts for a week, a phenomenon known as detraining sets in. During this period, your muscle glycogen stores start to shrink [3]. Glycogen is glucose stored in your muscles. It’s used as an energy source during exercise.
More importantly, glycogen binds to water. And when you lose glycogen, you also lose water. And since your muscles are ~76% water [6], they look smaller [3].
Hence, your apparent size loss isn't due to muscle atrophy. You just lost water [3].
The good news is that the water loss is temporary. You regain muscle glycogen and water when you resume your workouts.
Taking a week off from your workouts is a good thing
Taking a week off from training is known as a rest week or recovery week. It's a common practice in many sports.
A deload or rest week is usually added to the training programs of bodybuilders, powerlifters, and weightlifters [1].
A recovery week has 3 major benefits:
- It resensitizes your muscles to training stimuli.
- The rest you get can do wonders for your recovery.
- It prevents burnout and overtraining.
Think of it as hitting the reset button for your body.
A recovery week is similar to deloading, with one key difference:
- A deload week is a period where you intentionally reduce your training intensity and volume [1].
- A recovery week means a complete break from training.
The article continues below.
How Many Rest Days Do You Need in a Week? A Recovery Guide
Learn how many rest days you need per week. Recovery guidelines for athletes, gym goers, and beginners.
Can You Lose Muscle in a Week?
Under normal circumstances, you won’t lose muscle mass in a week.
By normal circumstances, I mean when you’re on vacation. Or perhaps you’re busy with other things, so you take a week off.
Most studies conclude it takes 3 weeks to lose muscle [4] [5] [7] [8].
But there are some circumstances where you could lose muscle in a week.
It is possible to lose muscle if you’re completely inactive
Complete inactivity is the biggest detriment to muscle mass.
This is what complete inactivity looks like:
- Bed rest
- Limb immobilization (cast or brace)
Bed rest or limb immobilization leads to much quicker muscle loss [2] [9]. If your leg is in a cast or brace, you could lose ~5% of your leg muscle in a week [9].
The graph below shows the data. One dot represents a study. You can clearly see that the longer the leg is immobilized, the more muscle is lost [9].
Solution: If your leg is in a brace, you could train your upper body instead.
Get enough protein and calories during inactivity
If you are ever immobilized, make sure to eat a high protein diet and get enough calories.
Aim for 1.6 to 2.2 grams of protein per kilogram of bodyweight. To find your maintenance calories, just Google “TDEE calculator”.
With that said, complete muscle disuse rarely happens. In most cases, you will be taking a normal training break.
Continue reading to learn how long your muscles last during normal circumstances.
How Long It Takes to Lose Muscle During a Break
How long does it take to lose muscle? It depends on how active or inactive you are. But not all size loss is muscle loss.
It takes 3 weeks to lose muscle mass
Studies say you have 3 weeks until muscles start to atrophy [4] [5] [7] [8]. This assumes that you’re doing everyday activities, and are not immobilized.
Check out the graph below. It’s from a study where participants were divided into two groups: black and white. The white group trained continuously, but the black group took a 3-week break every 6 weeks of training [8].
The black group did lose some muscle size during detraining. But they quickly regained it when they resumed training. After 24 weeks, their muscles had grown just as much as the white group. The only difference was the black group had 25% fewer training sessions [8].
Muscle mass comes back quickly due to muscle memory
Now let’s say you were to lose muscle mass. The good news is that you will regain it quickly when you start training again.
This is due to an effect called “muscle memory” [10] [11] [12].
In short, it means your muscles remember their old size and strength. So you get a boost during retraining.
If you want to know more about this topic, read our article about muscle memory.