Is Your Spine Becoming Less Symmetrical as You Age?

New research suggests that differences between the left and right multifidus muscles may be a sign of how the body changes with aging.

When we think about healthy aging, we often focus on things we can easily see.

Are you getting weaker?

Are you walking slower?

Are you having more difficulty getting up from a chair?

Are you losing your balance?

But there are also changes happening inside your body that may occur long before you notice a major change in your everyday abilities.

One of these changes may involve a group of small muscles along your spine called the multifidus.

Recent research has identified an interesting relationship between aging and asymmetry in multifidus muscle size—meaning the multifidus on one side of the spine may become different in size from the muscle on the other side.

The researchers suggest that this asymmetry may even become a signature of aging.

So what does that mean?

What is the multifidus?

The multifidus is a group of small muscles located along the spine.

These muscles don’t get the same attention as the large muscles in your legs, but they play an important role in spinal stability and control.

Think of them as part of your body’s built-in support system.

Every time you stand, walk, reach, bend, turn, or move your body, your spine needs to remain controlled.

The multifidus helps provide that control.

Unlike a large muscle such as the quadriceps, the multifidus is designed to provide precise, segmental control of the spine.

And because it plays such an important role in spinal stability, changes in the multifidus may tell us something about how the spine and surrounding muscles are adapting as we age.

What did the researchers discover?

In their study, researchers looked at the cross-sectional area (CSA) of the multifidus muscles on both sides of the spine.

They found an interesting relationship:

As age increased, asymmetry between the left and right multifidus appeared to increase.

In other words, the two sides of the back did not always change in exactly the same way.

One multifidus muscle could become smaller than the other.

This is called muscle asymmetry.

The researchers suggest that these asymmetrical changes may be associated with the normal adaptations that occur throughout the spine as we get older.

They even proposed that multifidus asymmetry may eventually become a potential imaging biomarker of aging.

That’s an intriguing idea.

But it is important to understand what the study does—and does not—tell us.

The researchers did not prove that multifidus asymmetry causes back problems.

They also did not establish that every person with multifidus asymmetry has a spinal problem.

Instead, they identified a relationship between aging and differences in multifidus muscle size and proposed several possible explanations.

Why might the two sides become different?

There are several possible reasons.

1. We don’t always use our bodies symmetrically

As we age, many people gradually develop changes in the way they stand and move.

Perhaps you shift your weight more onto one leg.

Maybe you rotate your trunk slightly when you stand.

Maybe one hip has become stiffer.

Maybe an old injury has changed the way you move.

Maybe you spend years favoring one side of your body.

These small changes may not seem important.

But repeated thousands of times over years, they can change how forces are distributed throughout the body.

The researchers suggest that these compensatory postural changes may place different amounts of compression and shear forces on different parts of the lumbar spine.

Over time, that may influence how the muscles surrounding the spine work.

2. Posture can influence muscle activity

Your muscles respond to the position of your body.

Change your posture, and you can change the demands placed on your muscles.

If your spine is consistently positioned differently on one side, the muscles responsible for stabilizing it may not have to work in exactly the same way.

The researchers suggest that altered posture may contribute to altered multifidus muscle activity.

Over time, differences in muscle activity could potentially contribute to differences in muscle size.

This is one reason why how you move may be just as important as how strong you are.

3. Changes in the discs may influence the muscles

The discs between the vertebrae naturally undergo changes as we age.

Disc degeneration is a common part of aging and does not automatically mean someone will have pain.

However, changes to the discs can sometimes contribute to changes in the way the spine moves or distributes load.

The researchers suggest that disc changes, including disc bulging, could potentially affect the multifidus differently on one side than the other.

Again, this is a proposed mechanism—not something this study definitively proved.

4. Nerve involvement may play a role

The researchers also discuss the possibility that changes in posture or spinal structures could result in subtle, one-sided nerve compression.

Because nerves help control muscles, changes in nerve input could potentially affect the size or activity of a muscle.

This provides another possible explanation for why one multifidus could become smaller than the other.

But there is still much to learn.

The authors specifically state that future research is needed to determine exactly why these asymmetrical changes occur.

Why does symmetry matter?

Your body isn’t perfectly symmetrical.

In fact, some differences between the right and left sides are completely normal.

The goal isn’t to make every muscle exactly the same size.

Instead, symmetry can provide useful information about how your body is distributing movement and load.

Think about your car.

If the tires aren’t aligned properly, the car may still drive.

But over thousands of miles, the uneven forces can cause certain components to wear differently.

Your body is considerably more complicated than a car, but the general concept is useful:

Repeated asymmetrical movement can change how forces are distributed.

That’s why looking at symmetry can be valuable when evaluating how someone moves and ages.

This is one reason we include the multifidus in the 6 Green Zones™

The 6 Green Zones™ are six areas of the body we believe deserve particular attention when evaluating physical performance and healthy aging.

They include:

• Shoulder – supraspinatus and rotator cuff
• Neck – cervical multifidus
• Thoracic spine – thoracic multifidus
• Lumbar spine – lumbar multifidus
• Hips – gluteus medius and gluteus minimus
• Calves – including the soleus

Notice something about this list.

We’re not simply looking at the biggest muscles in the body.

We’re looking at muscles that contribute to stability, posture, balance, movement control, and physical capacity.

And the multifidus is particularly interesting because it sits at the center of your body’s ability to control the spine.

It’s not just about strength

When people hear “muscle,” they often think about strength.

But strength is only one piece of the puzzle.

A healthy muscle needs to be able to:

Connect with the nervous system.

Control movement.

Work without excessive compensation.

Maintain adequate capacity.

And perform consistently over time.

This is the foundation of our Feel It to Heal It Physio™ approach.

We don’t simply want someone to perform an exercise.

We want them to understand where the movement should be coming from and whether the correct muscles are actually doing the work.

Could multifidus asymmetry be an early warning sign?

Possibly—but we need to be careful with that statement.

The researchers describe multifidus asymmetry as a potential signature of aging and a possible future imaging biomarker.

That does not mean that multifidus asymmetry is currently a diagnostic test for aging or spinal disease.

And it certainly doesn’t mean that asymmetry automatically means something is wrong.

Instead, the finding gives us another reason to pay attention to symmetry and muscle performance as we age.

That is why we ask you “where do you feel the muscle working?”

Because if you only feel the muscle on one side and not the other, that gives us a data point to address and work to improve.

That’s very different from simply asking:

“How much can you lift?”

Your body may compensate before you notice a problem

This may be one of the most important lessons from this research.

Your body is remarkably good at compensating.

If one muscle becomes weaker, another muscle may help.

If one joint becomes stiff, you may move through another joint.

If one side becomes less capable, you may unconsciously shift toward the other side.

And because these adaptations can happen gradually, you may not notice them.

You simply start moving differently.

That’s why evaluating movement before a major problem develops may be valuable.

Start with your 6 Green Zones™

The 6 Green Zones™ provide a way to look at important areas of the body that contribute to your physical foundation.

Rather than waiting until pain, weakness, or loss of balance forces you to pay attention, you can use an assessment to identify areas that may need more focus.

Because healthy aging isn’t just about adding years to your life.

It’s about maintaining your ability to move well, stay strong, remain balanced, and continue doing the things you enjoy.

Your chronological age tells you how long you’ve been alive.

Your physical performance tells you how your body is functioning today.

The 6 Green Zones™ can help you understand the difference.