Detraining calculator - How much you lose when you stop training
Strength training
By Jesús Narváez Tamés ·
Enter your weeks off, your level and your numbers, and see how much strength, muscle and endurance you lose according to the research, how long it takes to regain and how to come back week by week.
How much you lose when you stop training
Holidays, exams, an injury or a month of long hours at work: everyone takes breaks. The usual answer to "how much will I lose?" is "it depends". This calculator gives you the number. It uses the curves from detraining studies: strength and muscle hold for about 3 weeks with no measurable change and then drop slowly, while endurance (VO2max) starts falling in the first week and is 10–13% lower after 2 months in trained people.
With your 1RM and your 5K time it tells you where you are now, how many weeks it will take to get back to your level (regaining is faster than gaining it the first time) and a 1 to 4-week return plan with loads, sets and mileage. It is an average estimate: everyone responds differently, and with an injury your physio has the final say.
Squat, bench press, deadlift… whichever lift you like.
Training normally, you get back your strength in 1 week and your endurance in about 4 weeks. Regaining is faster than gaining it the first time.
If you look "flat" in the first week, that is glycogen and water, not muscle: it comes back after a few days of eating and training.
2-week return plan
Percentages are of your current 1RM, the one after the break, and volume is relative to what you did before. Leave the reps in reserve (RIR) shown.
- Week 1
Main lift: 3×8 · 72.5 % (160 lb) · RIR 3 · 60 % of your sets
Running: 60 % of your mileage, all easy
- Week 2
Main lift: 4×5 · 80 % (175 lb) · RIR 2 · 80 % of your sets
Running: 85 % of your mileage, easy + strides
Easy runs: 10:21–11:13 min/mi.
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Frequently asked questions
How much muscle do you lose in a month off?
Hardly any. Muscle mass does not drop measurably until about 3 weeks in, so after a month the loss is around 1%. What you notice earlier is that muscles look flatter because they store less glycogen and water, and that comes back within days.
How long does it take to lose strength?
Maximal strength holds for about 3 weeks. After that it drops slowly: around 4–7% by 8 weeks and 6–11% by 12 weeks, depending on your level. Advanced lifters lose a bit more because they are further from where they started.
What about endurance?
It is the first to go. VO2max drops 5–7% in 3 weeks and 10–13% in 8 weeks in trained runners, then levels off. That is why after a break your 5K pace suffers before your 1RM does.
Is muscle memory real?
Yes. The nuclei muscle fibres gain through training stay during a break, and regaining what you lost takes far less than building it the first time. As a rule, strength comes back in less than half the time you were off.
How should I return to training after a break?
Start with 50–60% of your previous sets, loads around 65–75% of your current 1RM and 3–4 reps in reserve. Build up each week to your normal volume over 2–4 weeks, depending on how long the break was. For running, keep the first week all easy at half your mileage.