How fitness age is calculated
First the tool gets your VO2max: either a number you measured, or an estimate from your maximum and resting heart rate with the heart rate ratio method 2. Then it finds the age at which the FRIEND registry median for your sex equals your VO2max, reading between the decade medians from the 20s to the 70s 1.
So a fitness age of 35 means your VO2max matches the median of people around 35 in FRIEND, a registry of treadmill tests in healthy adults aged 20–79 1. Values outside that span are shown as under 25 or over 75.
How to read your fitness age
A fitness age below your real age means your aerobic fitness is above the median for your age group. Higher cardiorespiratory fitness is associated with lower long-term mortality 3, so this is a useful number to watch over time.
It is not a biological age and says nothing about other parts of your health. Training moves it: interval and continuous training both raise VO2max 4. Retest after a few months of consistent work.
| Age | 25th | 50th (median) | 75th | 95th |
|---|---|---|---|---|
| 20–29 | 30.5 | 37.6 | 44.7 | 56.0 |
| 30–39 | 25.3 | 30.2 | 36.1 | 45.8 |
| 40–49 | 22.1 | 26.7 | 32.4 | 41.7 |
| 50–59 | 19.9 | 23.4 | 27.6 | 35.9 |
| 60–69 | 17.2 | 20.0 | 23.8 | 29.4 |
| 70–79 | 15.6 | 18.3 | 20.8 | 24.1 |
| Age | 25th | 50th (median) | 75th | 95th |
|---|---|---|---|---|
| 20–29 | 40.1 | 48.0 | 55.2 | 66.3 |
| 30–39 | 35.9 | 42.4 | 49.2 | 59.8 |
| 40–49 | 31.9 | 37.8 | 45.0 | 55.6 |
| 50–59 | 27.1 | 32.6 | 39.7 | 50.7 |
| 60–69 | 23.7 | 28.2 | 34.5 | 43.0 |
| 70–79 | 20.4 | 24.4 | 30.4 | 39.7 |
Questions people ask
What is fitness age?
Here it means the age at which your VO2max equals the median for your sex in the FRIEND reference data 1. It is a way of expressing aerobic fitness in years.
Can I lower my fitness age?
Yes, by raising your VO2max. A meta-analysis found large gains from both interval and continuous endurance training 4.
How accurate is it?
As accurate as the VO2max you put in. A lab-measured VO2max gives the best answer; a heart-rate estimate is rough, especially outside the well-trained men the method was developed in 2.
Is fitness age the same as biological age?
No. It only compares your aerobic fitness with reference medians 1. It does not measure ageing in your cells or organs.
Sources
- Kaminsky LA, Arena R, Myers J. Reference standards for cardiorespiratory fitness measured with cardiopulmonary exercise testing: data from the Fitness Registry and the Importance of Exercise National Database. Mayo Clin Proc. 2015;90(11):1515–1523.
- Uth N, Sørensen H, Overgaard K, Pedersen PK. Estimation of VO2max from the ratio between HRmax and HRrest: the Heart Rate Ratio Method. Eur J Appl Physiol. 2004;91(1):111–115.
- Mandsager K, Harb S, Cremer P, Phelan D, Nissen SE, Jaber W. Association of cardiorespiratory fitness with long-term mortality among adults undergoing exercise treadmill testing. JAMA Netw Open. 2018;1(6):e183605.
- Milanović Z, Sporiš G, Weston M. Effectiveness of high-intensity interval training (HIT) and continuous endurance training for VO2max improvements: a systematic review and meta-analysis of controlled trials. Sports Med. 2015;45(10):1469–1481.