Forget your age, your weight, even your step count.
There is one metric above all others, according to ISSA-certified personal trainer Connor Darnbrough, that determines how well you are likely to age.
"Your VO2 max, the maximum amount of oxygen your body can use during exercise, is the single strongest predictor of longevity," he tells Fit&Well.
It's more important, he says, than blood pressure, cholesterol and body mass index (BMI).
VO2 max is considered one of the most accurate ways of measuring cardiovascular fitness—indicating how efficiently your heart, lungs, and muscles can convert oxygen into energy.
One major 2018 study found participants with the highest—or elite—cardiorespiratory fitness had around five times lower mortality risk than those in the lowest fitness group.
Yet even moving from low fitness to average or above average was associated with a significant reduction in risk.
"The good news is that VO2 max is highly trainable at any age, including for complete beginners," says Darnbrough.
And the approach for older adults is more accessible than most people expect.
Darnbrough, who is co-founder of Smart Fit Method, says that to improve your VO2 max you should start by building your cardiovascular foundations with consistent training in the second of five heart rate zones, popularly known as zone 2 training.
"Zone 2 is any sustained aerobic activity where you can hold a full conversation, not gasping, not completely comfortable, but able to speak in complete sentences," he explains.
Walking briskly, light jogging, cycling at a moderate pace, or swimming steadily all qualify.
"At this intensity, your body builds the mitochondrial density and fat-burning efficiency that underlie all aerobic fitness," says Darnbrough.
Here is a beginner VO2 max workout you can use to build your aerobic capacity.
How to do the workout
Darnbrough recommends starting out with 20-30 minutes of brisk walking, light jogging, cycling or swimming at a zone 2 intensity three times per week.
"For beginners, this is the entire prescription to start," he says.
"No intervals. No intensity. Just consistency at a conversational pace. Most people see measurable improvements in how they feel and recover within four to six weeks."
Your target heart rate for zone 2 training is approximately 60-70% of your maximum.
If you don't have a suitable wearable device to read your pulse, Darnbrough says you can use the talk test.
"You should be able to speak a full sentence without pausing for breath," he says.
If that's easy, speed up slightly. If you need to take a breath mid-sentence, throttle down your pace to bring your heart rate back in check.
How to progress this VO2 max workout
Consistent zone 2 training for six to eight weeks should have built your base, says Darnbrough.
"Next, short high-intensity intervals layered on top will produce the largest VO2 max gains."
For older adults, he recommends this structure as an accessible way to introduce intervals safely:
- Warm-up at a light zone 2 intensity for five minutes.
- Alternate 30 seconds of harder effort with 90 seconds of easy recovery.
- Repeat this pattern for four to six intervals.
- Finish with a five-minute cool-down.
"The key is that the hard portions feel genuinely hard," he adds. "Not all-out, but uncomfortable enough that conversation is not possible."
This elevated intensity triggers the cardiovascular adaptations that raise VO2 max most effectively, he says.
For the best results, Darnbrough recommends pairing these cardiovascular workouts with strength training to helps build and preserve muscle mass.
"Muscle mass is metabolically active tissue," he explains.
"The more muscle mass you carry, the greater your body's capacity to absorb and use oxygen."
So in addition to protecting your joints and strengthening your muscles and bones, resistance training can raise your aerobic ceiling over time.
