1️⃣ It normally takes 3 weeks to lose muscle mass.
2️⃣ You could lose muscle quicker in some circumstances.
3️⃣ You will lose water and glycogen which makes you look smaller.
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 . Glycogen is glucose stored in your muscles. It’s used as an energy source during exercise.
Hence, your apparent size loss isn't due to muscle atrophy. You just lost water .
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 .
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 .
- A recovery week means a complete break from training.
The article continues below.
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.
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)
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 .
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.
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How Fast Do You Lose Muscle?
Muscle loss is relatively slow if you’re physically active.
Even if you’re not in the gym, everyday activities slow down muscle atrophy:
- Carrying or moving things
- Physical labor
The article continues below.
It takes 3 weeks to lose muscle mass
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 .
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 .
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.
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.
 Bell L, Nolan D, Immonen V, Helms E, Dallamore J, Wolf M, Androulakis Korakakis P. "You can't shoot another bullet until you've reloaded the gun": Coaches' perceptions, practices and experiences of deloading in strength and physique sports. Front Sports Act Living. 2022 Dec 21;4:1073223. doi: 10.3389/fspor.2022.1073223. PMID: 36619355; PMCID: PMC9811819.
 Dirks ML, Wall BT, van de Valk B, Holloway TM, Holloway GP, Chabowski A, Goossens GH, van Loon LJ. One Week of Bed Rest Leads to Substantial Muscle Atrophy and Induces Whole-Body Insulin Resistance in the Absence of Skeletal Muscle Lipid Accumulation. Diabetes. 2016 Oct;65(10):2862-75. doi: 10.2337/db15-1661. Epub 2016 Jun 29. PMID: 27358494.
 Encarnação IGA, Viana RB, Soares SRS, Freitas EDS, de Lira CAB, Ferreira-Junior JB. Effects of Detraining on Muscle Strength and Hypertrophy Induced by Resistance Training: A Systematic Review. Muscles. 2022; 1(1):1-15. doi: 10.3390/muscles1010001
 Gavanda S, Geisler S, Quitmann OJ, Bauhaus H, Schiffer T. Three Weeks of Detraining Does Not Decrease Muscle Thickness, Strength or Sport Performance in Adolescent Athletes. Int J Exerc Sci. 2020 May 1;13(6):633-644. PMID: 32509134; PMCID: PMC7241623.
 Lorenzo I, Serra-Prat M, Yébenes JC. The Role of Water Homeostasis in Muscle Function and Frailty: A Review. Nutrients. 2019 Aug 9;11(8):1857. doi: 10.3390/nu11081857. PMID: 31405072; PMCID: PMC6723611.
 Ogasawara R, Yasuda T, Sakamaki M, Ozaki H, Abe T. Effects of periodic and continued resistance training on muscle CSA and strength in previously untrained men. Clin Physiol Funct Imaging. 2011 Sep;31(5):399-404. doi: 10.1111/j.1475-097X.2011.01031.x. Epub 2011 May 31. PMID: 21771261.
 Ogasawara R, Yasuda T, Ishii N, Abe T. Comparison of muscle hypertrophy following 6-month of continuous and periodic strength training. Eur J Appl Physiol. 2013 Apr;113(4):975-85. doi: 10.1007/s00421-012-2511-9. Epub 2012 Oct 6. PMID: 23053130.
 Preobrazenski N, Seigel J, Halliday S, Janssen I, McGlory C. Single-leg disuse decreases skeletal muscle strength, size, and power in uninjured adults: A systematic review and meta-analysis. J Cachexia Sarcopenia Muscle. 2023 Apr;14(2):684-696. doi: 10.1002/jcsm.13201. Epub 2023 Mar 7. PMID: 36883219; PMCID: PMC10067508.
 Rahmati M, McCarthy JJ, Malakoutinia F. Myonuclear permanence in skeletal muscle memory: a systematic review and meta-analysis of human and animal studies. J Cachexia Sarcopenia Muscle. 2022 Oct;13(5):2276-2297. doi: 10.1002/jcsm.13043. Epub 2022 Aug 12. PMID: 35961635; PMCID: PMC9530508.
 Snijders T, Aussieker T, Holwerda A, Parise G, van Loon LJC, Verdijk LB. The concept of skeletal muscle memory: Evidence from animal and human studies. Acta Physiol (Oxf). 2020 Jul;229(3):e13465. doi: 10.1111/apha.13465. Epub 2020 Apr 3. PMID: 32175681; PMCID: PMC7317456.