How to Find Out Your Fitness Age

Your chronological age is easy to calculate.

You simply count the number of years since you were born.

But what about your fitness age?

Fitness age is an attempt to answer a different question:

How does your physical fitness compare with what might be expected for someone your age?

Today, there are several ways to estimate it.

You may have seen fitness age calculated from a smartwatch, fitness tracker, VO₂max estimate, heart rate data, activity levels, or even blood-based biomarkers.

These approaches can provide useful information.

But there is another question worth asking:

What if your fitness age isn’t just about how well your heart and lungs perform?

What if it also includes how well your body moves, stabilizes, balances, produces strength, and performs the physical tasks you need every day?

That’s where PhysioFit Age™ takes a different approach.

How Is Fitness Age Usually Measured?

There isn’t one universal definition or test for “fitness age.”

Different systems use different measurements.

Some focus primarily on cardiorespiratory fitness, often using VO₂max or an estimate of VO₂max.

Others incorporate:

• Resting heart rate
• Heart-rate response to exercise
• Physical activity
• Sleep
• Body composition
• Blood biomarkers
• Metabolic measurements
• Wearable-device data

Modern wearable technology has made this information increasingly accessible.

Research has demonstrated that wearable sensors can estimate cardiorespiratory fitness from real-world activity and heart-rate data, providing estimates that can correlate reasonably well with laboratory VO₂max testing.

And this technology continues to evolve.

A 2026 study, for example, examined a wearable-derived cardiovascular fitness age in 442 adults and found that the estimate changed alongside measures such as estimated VO₂max, resting heart rate, daily steps, and sleep-related measures.

This is exciting technology.

But it raises an important question:

Is cardiorespiratory fitness the whole story?

VO₂max Is Important—but It Doesn’t Tell You Everything

VO₂max is a valuable measure of cardiorespiratory fitness.

It tells us about your body’s ability to take in, transport, and use oxygen during exercise.

Higher cardiorespiratory fitness is associated with better health outcomes, making VO₂max an important measure of fitness.

But imagine two people with the exact same VO₂max.

Person A can run or cycle efficiently but has difficulty getting off the floor, balancing on one leg, or reaching overhead.

Person B has the same VO₂max but can easily squat, climb stairs, balance, carry groceries, get up from the floor, and perform household activities.

Would you consider them equally physically capable?

Probably not.

That’s because fitness is more than cardiovascular fitness.

Your Body Has More Than One Type of Fitness

Your ability to function physically depends on multiple systems working together.

You need:

Cardiorespiratory fitness

to keep moving for longer periods.

Muscular strength

to produce force.

Muscular endurance

to keep producing force repeatedly.

Balance

to maintain control of your body.

Mobility

to move your joints through the ranges you need.

Coordination and motor control

to organize movement effectively.

Stability

to control your body while you move.

These qualities don’t necessarily decline at exactly the same rate.

Research examining physical performance across adulthood found that different aspects of physical function can begin showing age-related changes at different points in life. Balance and chair-stand performance showed changes as early as the fifth decade, while gait speed and aerobic endurance showed changes later.

That is an important insight.

You can be “fit” in one area and have opportunities for improvement in another.

Your Fitness Tracker May Know Your Heart. Does It Know Your Body?

Your wearable may tell you:

• How many steps you took
• How many calories you burned
• Your resting heart rate
• Your estimated VO₂max
• How long you slept
• How active you were today

That’s useful information.

But it may not tell you:

• Whether your right hip is doing more work than your left
• Whether your shoulder has enough stability
• Whether your deep neck muscles are activating effectively
• Whether your lumbar spine has adequate muscular control
• Whether your calves have enough endurance
• Whether you can stabilize your pelvis during a single-leg movement
• Whether you’re compensating for weakness somewhere else

These are different questions.

And they’re questions about physical performance, not simply activity.

There’s a Difference Between Exercising and Performing

Consider this:

You might exercise five days a week.

But can you get up from the floor?

Can you climb stairs comfortably?

Can you carry your groceries?

Can you walk through a large store without needing to sit down?

Can you balance when you step over something?

Can you reach overhead without discomfort?

Can you perform household or yard activities confidently?

Can you strength train consistently?

These are examples of functional fitness.

They describe what your body can actually do.

And that’s an important part of aging well.

The 6 Green Zones™: Looking at How Your Body Performs

This is where the 6 Green Zones™ approach comes in.

Rather than looking at physical fitness through one measurement, the 6 Green Zones™ examine six key regions of the body that contribute to movement, strength, stability, and physical control.

1. Shoulder

The shoulder Green Zone™ focuses on the rotator cuff, including the supraspinatus.

Your shoulders allow you to reach, lift, carry, push, pull, and interact with your environment.

Shoulder strength and control can become especially important for everyday activities such as reaching into cabinets, putting on clothing, and lifting objects.

2. Neck

The neck Green Zone™ focuses on the cervical multifidi.

These deep muscles contribute to cervical stability and control.

Your neck also interacts with your visual and balance systems, making head and neck control an important part of how you orient yourself in your environment.

3. Thoracic Spine

The thoracic spine Green Zone™ focuses on the thoracic multifidi.

Your mid-back contributes to trunk stability, posture, and the ability to move your upper body effectively.

It provides an important connection between the upper and lower portions of your body.

4. Lumbar Spine

The lumbar spine Green Zone™ focuses on the lumbar multifidi.

Your low back needs to provide enough stability and control to allow your arms and legs to move efficiently.

Walking, bending, lifting, carrying, and transitioning between positions all require coordinated trunk control.

5. Hips

The hip Green Zone™ focuses on the gluteus medius and gluteus minimus.

Your hip muscles play an important role in pelvic stability and single-leg control.

Walking, climbing stairs, stepping over obstacles, and maintaining balance all require your hips to help control your body.

6. Calves

The calf Green Zone™ focuses particularly on the soleus and the muscles responsible for ankle and lower-leg function.

Your calves contribute to walking, push-off, standing, and postural control.

They are an important part of the foundation that supports your movement.

Why These Six Areas?

The 6 Green Zones™ aren’t intended to represent every muscle or every factor that contributes to physical fitness.

Instead, they provide a focused framework for evaluating important components of physical performance.

We look at areas such as:

Strength

Muscle activation

Stability

Symmetry

Endurance

Control

This creates a different picture than simply asking how many steps you took today or what your estimated VO₂max happens to be.

Strength Doesn’t Always Mean Performance

Here’s another important distinction.

A muscle can have the ability to produce force without necessarily performing optimally during movement.

Your nervous system needs to activate the appropriate muscles at the appropriate time.

Your muscles need to coordinate with one another.

Your body needs to control the force it produces.

And you need to be able to repeat that performance when you’re tired.

Research on physical performance in older adults has found relationships between muscle strength and functional measures such as balance, walking, and other physical tasks.

This is why functional fitness is about more than isolated strength.

It’s about how your strength translates into movement.

What If Your Fitness Age and Physical Performance Don’t Match?

Imagine someone has an excellent cardiovascular fitness age but struggles with balance.

Or someone has a high daily step count but has significant weakness in one hip.

Or someone exercises regularly but has difficulty getting up from the floor.

These aren’t contradictions.

They simply show that fitness has multiple dimensions.

A person can have excellent cardiovascular capacity and still have an area of musculoskeletal weakness or poor motor control.

That’s not a failure.

It’s useful information.

Because once you know where the opportunity is, you can create a strategy.

PhysioFit Age™ Goes Beyond Simply Measuring How Much You Exercise

This is the key difference.

PhysioFit Age™ goes beyond simply measuring how much you exercise. It looks at how your body performs.

Rather than focusing only on how active you are, the goal is to understand how your body is functioning.

Can your muscles activate?

Can you produce and control force?

Can you maintain stability?

Can you move symmetrically?

Can you maintain endurance?

Can you control your body during movement?

These are important questions when the goal isn’t simply to exercise more—but to maintain physical capacity as you age.

Your PhysioFit Age™ Is a Snapshot, Not a Prediction

It’s important to understand what a fitness age or PhysioFit Age™ can and cannot tell you.

It isn’t a crystal ball.

It doesn’t tell you exactly how long you’ll live.

It doesn’t diagnose disease.

And it shouldn’t replace appropriate medical evaluation.

Instead, PhysioFit Age™ is intended as a snapshot of physical performance relative to chronological age.

Think of it as a way to answer:

“How is my body performing right now?”

And perhaps even more importantly:

“Where do I have an opportunity to improve?”

The Goal Isn’t to Have the Youngest Fitness Age

You don’t need your body to perform like a 25-year-old forever.

The goal is to maintain the physical abilities that allow you to live the life you want.

You want to be able to:

• Walk comfortably
• Climb stairs
• Get up from a chair
• Get on and off the floor
• Carry groceries
• Work around your house
• Enjoy your hobbies
• Travel
• Exercise
• Maintain your independence

That’s what makes physical performance meaningful.

Your Fitness Age Should Help You Do Something With the Information

A number by itself isn’t necessarily helpful.

Knowing that your estimated cardiovascular fitness age is 5 years younger than your chronological age might feel good.

But what do you do with that information?

The real value comes when measurement leads to action.

Measure.

Understand.

Improve.

Re-test.

That’s the philosophy behind the 6 Green Zones™ approach.

Find the Areas That May Be Missing

You may already have excellent cardiovascular fitness.

You may walk thousands of steps every day.

You may have a great workout routine.

But there may still be areas of your physical performance that deserve attention.

Maybe your hip stability needs work.

Maybe your calf endurance has declined.

Maybe your shoulder doesn’t have the control it once did.

Maybe your trunk stability could improve.

Maybe your neck control isn’t where you want it to be.

The goal isn’t to find problems.

It’s to find opportunities.

Once you know where those opportunities are, you can create a more targeted strategy.

From Measurement to Healthspan

This is ultimately why measuring physical performance matters.

Longevity is about how long you live.

Healthspan is about how well you can live during those years.

Being able to walk, exercise, travel, get up from the floor, work around the house, play with your grandchildren, and participate in the activities you enjoy requires physical capacity.

That capacity doesn’t come from one number.

It comes from multiple systems working together.

Your heart and lungs matter.

Your muscles matter.

Your balance matters.

Your mobility matters.

Your nervous system matters.

And your ability to coordinate all of them matters.

So, How Do You Find Out Your Fitness Age?

There isn’t just one answer.

You can learn about your cardiovascular fitness through measures such as VO₂max.

Wearables can provide useful information about activity and cardiorespiratory fitness.

Blood-based and other biological measures may provide additional information about aging and health.

But if you want to understand how your body actually performs, you need to look beyond cardiovascular fitness alone.

That’s where the 6 Green Zones™ can provide another perspective.

And that’s where PhysioFit Age™ comes in.

PhysioFit Age™ goes beyond simply measuring how much you exercise. It looks at how your body performs.

Your chronological age tells you how many years you’ve lived.

Your PhysioFit Age™ provides a snapshot of your physical performance relative to that age.

The goal isn’t simply to get a younger number.

The goal is to understand your body, identify opportunities to improve, and build the physical capacity to keep doing the things that matter to you.

Discover Your 6 Green Zones™

Your fitness tracker can tell you how much you moved.

Your VO₂max can tell you something about your cardiovascular fitness.

Your blood work can provide information about what’s happening inside your body.

The 6 Green Zones™ ask a different question:

How is your body performing?

Discover your 6 Green Zones™, learn your PhysioFit Age™, and identify the areas where you may have an opportunity to improve your physical performance—and ultimately support a longer, more capable healthspan.

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Scientific References

Physical Performance Across the Adult Life Span: Correlates With Age and Physical Activity. This study examined adults from age 30 through 90+ and found that physical performance—including mobility, strength, endurance, and balance—changes across the lifespan, with different components showing age-related changes at different times.

Longitudinal cardio-respiratory fitness prediction through wearables in free-living environments. This study demonstrated that wearable sensor data can be used to estimate cardiorespiratory fitness in real-world settings, with wearable-derived estimates correlating with laboratory measures of VO₂max.

Wearable-derived cardiovascular fitness age and its lifestyle correlates in 442 adults. Published in 2026, this study examined a wearable-derived cardiovascular fitness age and its relationship with measures including daily steps, sleep, resting heart rate, and estimated VO₂max.

Muscle Mass and Muscle Strength Relationships to Balance: The Role of Age and Physical Activity. This study found positive relationships between muscle strength and balance in older adults, with the relationships particularly evident among less active and older participants.

Functionality, muscular strength and cardiorespiratory capacity in the elderly. This research demonstrated relationships between strength, cardiorespiratory capacity, and functional measures such as the Timed Up and Go, gait speed, chair-stand performance, and overall physical performance.