Detraining Fitness Decay
Calculator
Results
- Final VO2max
- 37.125 vo2max
- Total lost
- 14.875 vo2max
- Share of peak retained
- 71.39423%
- Effective half-life
- 8 wk
Projected path over the weeks
- VO2max
- Baseline VO2max
Week-by-week schedule
| 1 | 50.59 | 1.41 | 97.29 | 50.59 |
| 2 | 49.30 | 2.70 | 94.80 | 49.30 |
| 3 | 48.11 | 3.89 | 92.52 | 48.11 |
| 4 | 47.02 | 4.98 | 90.42 | 47.02 |
| 5 | 46.02 | 5.98 | 88.51 | 46.02 |
| 6 | 45.11 | 6.89 | 86.75 | 45.11 |
| 7 | 44.27 | 7.73 | 85.13 | 44.27 |
| 8 | 43.50 | 8.50 | 83.65 | 43.50 |
| 9 | 42.79 | 9.21 | 82.30 | 42.79 |
| 10 | 42.15 | 9.85 | 81.05 | 42.15 |
| 11 | 41.55 | 10.45 | 79.91 | 41.55 |
| 12 | 41.01 | 10.99 | 78.87 | 41.01 |
| 13 | 40.51 | 11.49 | 77.91 | 40.51 |
| 14 | 40.05 | 11.95 | 77.03 | 40.05 |
| 15 | 39.63 | 12.37 | 76.22 | 39.63 |
| 16 | 39.25 | 12.75 | 75.48 | 39.25 |
| 17 | 38.90 | 13.10 | 74.80 | 38.90 |
| 18 | 38.57 | 13.43 | 74.18 | 38.57 |
| 19 | 38.28 | 13.72 | 73.61 | 38.28 |
| 20 | 38.01 | 13.99 | 73.09 | 38.01 |
| 21 | 37.76 | 14.24 | 72.61 | 37.76 |
| 22 | 37.53 | 14.47 | 72.17 | 37.53 |
| 23 | 37.32 | 14.68 | 71.76 | 37.32 |
| 24 | 37.13 | 14.88 | 71.39 | 37.13 |
Comparison
| Scenario | Final VO2max | Total lost |
|---|---|---|
| Doing nothing | 37.13 | 14.88 |
| Your plan | 37.13 | 14.88 |
Formula
V(t) = floor + (V₀ − floor) × 2^(−t/h), h′ = h ÷ (1 − maintained share)= 37.13
Note
These are deliberately simplified models. They assume a constant rate and ignore metabolic adaptation, water weight, hormones, illness, medication, sleep and stress, so individual results vary widely — two people following the same plan can land far apart. The 7700 kcal per kilogram of body fat figure is a population average, not a personal constant. A large deficit, a fast mileage or load ramp, or a very low target body fat can be harmful; treat any flagged rate as a reason to slow down. This is NOT medical, dietetic or coaching advice — consult a qualified doctor, registered dietitian or accredited coach before acting on any projection here, and especially if you are pregnant, under 18, or managing any medical condition.
More in Health progress
See all →Frequently asked questions
How quickly does fitness decline after I stop training?+
Cardiovascular fitness (VO2 max) typically begins measurably declining within about 2 weeks of inactivity and continues at a faster relative rate than strength, which is generally better preserved over short breaks.
Does strength decline as fast as cardio fitness during a break?+
No — strength is usually more resilient to short layoffs than aerobic capacity, with noticeable strength loss typically taking longer to appear, especially if the break is under a few weeks, though it does eventually decline with extended inactivity.
Is detraining the same as losing all my previous gains?+
No — there's a well-documented 'muscle memory' effect where previously trained muscle regains size and strength faster upon returning to training than it took to build originally, so a break doesn't erase progress as completely as the raw fitness numbers might suggest.
Does age affect how fast fitness is lost during detraining?+
Yes, generally — older individuals tend to lose conditioning somewhat faster and regain it more slowly than younger people, which is a factor worth accounting for when planning how much of a break is manageable.
How should I resume training after a break to avoid injury?+
Ease back in at a noticeably lower intensity and volume than where you left off, since connective tissue and neuromuscular coordination lag behind the return of general fitness — jumping back to your previous training load risks injury even if you feel capable.