6 OCTOBER 2026 · LEE C. STONEHOUSE
VO2max After 40: The Fitness Number That Predicts How Well You Age
THE NUMBER THAT MATTERS
Fitness is not just about appearance
After 40, fitness becomes less about proving what the body can do once and more about preserving what it can continue to do.
That is where VO2max matters.
VO2max measures the maximum amount of oxygen the body can use during intense exercise. It reflects how effectively the lungs take in oxygen, how efficiently the heart delivers it, and how well the muscles use it to produce energy.
It is a practical measure of cardiorespiratory fitness. It is also one of the most useful performance markers for understanding how well the body is coping with aging.
This is not a magic number. It is not a complete biological age test. But it is a powerful signal.
Low fitness can indicate reduced physiological reserve. Higher fitness generally means more capacity for movement, recovery and daily function.
Passive decline is not the only option.
WHAT THE RESEARCH SHOWS
Higher fitness is linked to better survival
A large 2018 study published in JAMA Network Open, led by Mandsager and colleagues, examined exercise treadmill data from 122,007 adults. The study found a graded relationship between cardiorespiratory fitness and mortality: as fitness increased, mortality risk decreased.
The relationship continued across the fitness scale. It was not limited to elite athletes.
The researchers also reported that participants in the highest fitness category had substantially lower mortality than those in the lowest category. The finding matters because it supports a practical message: moving out of poor fitness may be more important than chasing athletic perfection.
Read the study: Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing.
A separate review by Kodama and colleagues, published in JAMA, examined cardiorespiratory fitness and mortality risk. It reported that relatively modest improvements in fitness were associated with meaningful reductions in mortality risk.
These are observational findings. They show association, not a guarantee that improving VO2max alone will prevent disease or extend an individual’s life. Still, the pattern is consistent enough to make VO2max worth measuring.
VO2max is a reserve marker
The body needs reserve.
Reserve is the difference between what the body can do during an ordinary day and what it can do when demand rises. Walking uphill, carrying luggage, recovering from illness, playing with grandchildren and climbing stairs all draw on that reserve.
A higher VO2max generally gives a person more room before effort becomes overwhelming.
That matters for healthspan. A longer life is not enough if the later years are dominated by weakness, breathlessness and dependence. Healthspan means preserving the ability to move, think, participate and contribute.
VO2max cannot measure every part of healthspan. It does not directly assess muscle strength, body composition, sleep, blood glucose, stress or social connection.
It does, however, measure a central part of physical capability.
THE BIOLOGICAL AGE CONNECTION
A useful marker, not a complete diagnosis
A biological age test should use multiple markers rather than relying on one number.
The AGING?F***THAT! method uses a multivariate assessment built around independent laboratory data. VO2max contributes a different type of information: it shows how the integrated cardiovascular and muscular systems perform under demand.
That distinction matters.
A person may have favourable blood markers but poor cardiorespiratory fitness. Another may have a strong VO2max but need to improve sleep, body composition or metabolic health. A credible age-reversal strategy must identify the full pattern before deciding what to change.
VO2max should therefore be treated as one important panel in a larger dashboard.
Lee C. Stonehouse understands this from direct experience. He became a personal trainer at 21 in California after competing as a bodybuilder. He describes having had more wealth than health before he began his own turnaround in 2015.
He wrote The Healthspan Extension Manual and built the 10-Tenet operating system used by AGING?F***THAT!. His own biological age was assessed at 47 against a chronological age of 63: a 16-year divergence. He still trains, still tracks performance and still gets measured.
The principle is straightforward:
Measure. Intervene. Verify. Repeat.
HOW VO2MAX CHANGES AFTER 40
Aging changes the baseline. It does not decide the outcome.
VO2max tends to decline with age when training, movement and recovery are neglected. The rate is not identical for everyone. Training history, body composition, smoking, illness, medication, sleep and genetics all influence the result.
The mistake is treating decline as automatic and untouchable.
A person who has spent years inactive may have considerable room to improve. Someone who already trains may need a more precise programme to maintain performance or make smaller gains.
The target is not necessarily an elite score. The first target may be moving out of the lowest fitness category. The next may be maintaining capacity through the next decade.
That is why a baseline matters. Without a measurement, there is no reliable way to know whether a programme is working.
BUILD THE ENGINE
Aerobic training with a purpose
Improving VO2max usually requires a combination of training intensities.
Steady aerobic work helps build an endurance base. It allows the body to practise using oxygen efficiently for sustained periods.
Higher-intensity intervals place greater demand on the cardiovascular system. They can be effective, but they also require appropriate progression, recovery and individualisation.
The correct starting point depends on current fitness. Someone returning after years away from exercise should not copy the programme of a trained athlete.
A qualified professional can help determine suitable exercise selection, intensity and progression. Anyone with symptoms, a diagnosed condition or concerns about starting vigorous exercise should seek appropriate medical guidance before beginning.
The method should be challenging enough to create adaptation, but controlled enough to repeat.
Consistency beats occasional heroics.
Strength training over 50
Cardiorespiratory fitness is only one side of physical capability.
Strength training over 50 helps preserve the muscle, stability and force production needed to use aerobic capacity in real life. A strong heart and lungs are valuable. They become more useful when the legs, hips, back and upper body can translate that capacity into movement.
Resistance training can support:
- Muscle retention.
- Balance and control.
- Bone-loading activity.
- Everyday lifting and carrying.
- Confidence during movement.
- Independence later in life.
The strongest longevity strategy is not cardio versus weights. It is an operating system that includes both.
VO2max supports endurance. Strength supports function. Mobility supports access to movement. Recovery allows adaptation.
TEST, TRACK, IMPROVE
How to measure VO2max
There are three common approaches.
1. Laboratory testing
A direct VO2max test uses a treadmill or cycle ergometer, a face mask and breath-by-breath analysis. It can provide a detailed assessment of oxygen uptake, heart-rate response and exercise performance.
2. Submaximal testing
A submaximal protocol estimates VO2max from exercise performance and heart-rate response without requiring maximal effort. It can be useful for tracking change, although it is less direct than laboratory testing.
3. Wearable estimates
Some watches and fitness devices estimate VO2max from pace, heart rate and training data. These estimates can help identify trends, but they should not be treated as equivalent to a properly controlled laboratory assessment.
Whichever method is used, the key is consistency. Repeating a comparable test under similar conditions makes the trend more useful.
A single score is a snapshot. A sequence of scores shows direction.
FROM DATA TO ACTION
A practical four-step framework
1. Establish the baseline.
Measure VO2max alongside relevant health, lifestyle and body-composition data. Record current training, recovery and constraints.
2. Identify the limiting factor.
The issue may be low aerobic capacity, poor recovery, excess body fat, weak lower-body strength or inconsistent training. Guessing wastes time.
3. Apply the intervention.
Build an appropriate combination of aerobic conditioning, resistance training, nutrition, sleep and stress control.
4. Verify the result.
Repeat the relevant assessments. If performance has not improved, change the plan rather than defending it.
This is the difference between having fitness information and using fitness information.
The AGING?F***THAT! approach connects these decisions through its 10-Tenet operating system. Exercise does not operate in isolation. Nutrition, sleep, stress control, consistency and body composition all affect the result.
For the full framework, explore the AGING?F***THAT! age reversal programme.
THE BIGGER PURPOSE
Stay capable for the people who matter
VO2max is a number. Capability is the outcome.
The objective is to remain able to travel, work, train, play, carry, climb, contribute and participate. It is to remain present for family without becoming defined by avoidable decline.
That requires more than motivation. It requires measurement and repetition.
Lee C. Stonehouse built his method around the belief that aging should be challenged with evidence, not simply accepted as an identity. His own continuing assessments reinforce the point: the system must be practised, tested and refined.
The next step is not to chase a perfect score.
It is to find the current starting point, improve what can be improved and protect the capacity that makes the second half of life worth living.
DEEP DIVE: CREDIBLE SOURCES
- Mandsager et al., JAMA Network Open: Cardiorespiratory Fitness and Long-term Mortality
- Kodama et al., JAMA: Cardiorespiratory Fitness as a Quantitative Predictor of All-Cause Mortality
- Ross et al., Journal of the American College of Cardiology: Importance of Assessing Cardiorespiratory Fitness in Clinical Practice
- European Association of Preventive Cardiology: Cardiorespiratory Fitness and Health Outcomes
- World Health Organization: Physical Activity Guidelines
FAQ
What is a good VO2max after 40?
There is no single score that defines “good” for every person. Results should be interpreted against age, sex, training history and test method. The first practical objective is to move out of a low fitness category, then improve or preserve the result through progressive aerobic training and consistent recovery.
Can VO2max increase after 50?
Yes, VO2max can improve after 50 when training is appropriate and repeated consistently. The potential change depends on starting fitness, health, body composition, exercise history and recovery. Progress should be gradual. A controlled baseline test and repeat assessment can show whether the programme is producing measurable adaptation.
Is VO2max the same as biological age?
No. VO2max is one marker of cardiorespiratory fitness, not a complete biological age assessment. A broader biological age test should consider multiple laboratory and functional measures. VO2max can contribute valuable information because it reflects integrated performance under exercise stress, but it should be interpreted alongside other health data.
Is strength training important for healthspan after 50?
Yes. Strength training supports muscle retention, balance, force production and everyday function. It complements aerobic conditioning rather than replacing it. A healthspan-focused programme generally needs both cardiorespiratory fitness and strength, alongside nutrition, sleep, stress control and body-composition management.
How often should VO2max be tested?
The appropriate testing interval depends on the purpose, programme and test method. Testing too frequently may not allow enough time for meaningful adaptation. A professional may use a baseline assessment and repeat it after a structured training period, while wearable estimates can be used more regularly to observe trends.
READY TO MEASURE?
For readers within a 10 mile radius of Brighton & Hove city centre, the next step is a direct conversation about measurement, training and healthspan.
Contact Lee exclusively on WhatsApp by voice note, text message or voice call.
Is it time to stop guessing and measure the fitness that will support the years ahead?