How fast do you lose VO2 max when you stop?
Fast at first. Trained people lost 7 percent in three weeks and 16 percent by eight, then held, still above people who had never trained. Three weeks in bed at 20 cost five young men more than 30 years of aging did.
A week off for a cold or a trip feels like it might undo months of work, and a long break feels like starting over. Neither is quite right. The first few weeks of doing nothing cost a lot, the loss then levels off, and a trained body keeps some of what it built even after months.
We’d keep some cardio going through a busy month or an injury, even short walks or a bike, because the steepest loss comes in the first three weeks of doing nothing at all.
The curve
In 1984, researchers followed seven endurance-trained people who stopped training completely, and tested them at 12, 21, 56 and 84 days.
| Days off | VO2 max |
|---|---|
| 21 | 7 percent lower |
| 56 | 16 percent lower, where it settled |
| 84 | Still higher than in people who had never trained (50.8 against 43.3) |
The early drop came from the heart pumping less blood per beat. The later drop came from the muscles pulling less oxygen out of the blood. Even after 84 days, their muscles still had 50 percent more tiny blood vessels than the untrained group’s.
For a man in his 40s at 46.5, about the 82nd percentile, a 16 percent loss means about 39, or the 64th percentile. That’s a real drop, and he’d still be above the middle for his age.
Three weeks in bed against 30 birthdays
In 1966, five healthy 20-year-old men in Dallas spent three weeks in bed for a study of bed rest and training. Thirty years later, the same five came back to be tested again at 50.
Over those 30 years, their VO2 max had fallen only 11 percent in liters of oxygen a minute, from 3.30 to 2.90. The researchers wrote that the three weeks of bed rest at 20 had a more profound effect on their physical work capacity than three decades of aging. Six months of training at 50 then brought them back to 3.3 liters a minute, where they’d started at 20.
How to tell what you lost
A watch can’t tell you much in the first couple of weeks back. A 2022 review of 14 wearable studies put a meaningful change at 1.75 to 3.5 points, smaller than a single watch’s error. Retest with the same field test you used before the break, about 8 weeks after you restart (see how can I test my VO2 max at home?).
If the number fell and you didn’t take time off, the cause is more likely the watch than your heart. See why did my VO2 max drop?
5 sources
- Coyle EF and others, Time course of loss of adaptations after stopping prolonged intense endurance training, Journal of Applied Physiology, 1984europepmc.org
- McGuire DK and others, A 30-year follow-up of the Dallas Bedrest and Training Study: I. Effect of age on the cardiovascular response to exercise, Circulation, 2001europepmc.org
- McGuire DK and others, A 30-year follow-up of the Dallas Bedrest and Training Study: II. Effect of age on cardiovascular adaptation to exercise training, Circulation, 2001europepmc.org
- Kaminsky LA and others, Updated reference standards for cardiorespiratory fitness measured with cardiopulmonary exercise testing (FRIEND), Mayo Clinic Proceedings, 2022mayoclinicproceedings.org
- Molina-Garcia P and others, Validity of estimating the maximal oxygen consumption by consumer wearables: a systematic review with meta-analysis and expert statement of the INTERLIVE network, Sports Medicine, 2022pmc.ncbi.nlm.nih.gov
