Part 1 of a three-part series exploring muscle, metabolism, and what happens to blood sugar after it enters the bloodstream.
Long before I began having the conversations about wellness that I have today, I spent ten years working with the human body in a very different way.I was a massage therapist, but probably not in the way most people picture massage therapy. Relaxation massage was never really my thing.
I studied with a Rolfer and became deeply interested in structural integration — how muscles, fascia, posture, movement patterns, and compensation affect one another. Much of my work involved soft-tissue problems and chronic issues that hadn't necessarily responded to the usual approaches.
I also had the opportunity to work with professional athletes, as well as plenty of people who would never describe themselves as athletes but were dealing with pain or limitations that interfered with everyday life.
That work taught me something about the human body that has stayed with me ever since:
Where you feel the problem isn't necessarily where the problem begins.
A painful knee may have you looking at the hip. A shoulder problem may lead you somewhere entirely different. One structure compensates for another, movement changes, tension develops, and eventually the body tells you about it — sometimes a long way from where the story started.
It taught me to look beyond the obvious. So when I recently came across research involving a muscle buried deep in the calf, it immediately caught my attention.
Not because researchers had discovered some new muscle.
We've known about the soleus for a very long time.
It sits underneath the larger gastrocnemius — the prominent calf muscle most of us can see and feel. Anyone who studies anatomy learns what the soleus does mechanically. It helps point the foot downward, contributes to standing and walking, and plays an important role in posture and stability.
But researchers have been asking a different question about it.
What is this muscle doing metabolically?
And that's where the story becomes much more interesting.
Because the soleus may be doing considerably more than helping us stand and move our ankles.
A Muscle Built for a Different Kind of Work
Not all muscle fibers are designed to do the same thing.
Some are particularly good at producing short bursts of power. Others are designed to keep working for long periods without becoming easily fatigued.
The soleus contains a large proportion of those endurance-oriented, slow-twitch muscle fibers.
That makes perfect sense when you consider its job.
The soleus helps keep us upright. When we're standing and moving throughout the day, it can quietly work in the background for hours.
But researchers at the University of Houston became interested in something else.
They wanted to know what happened metabolically when they activated the soleus in a very specific way while a person remained seated.
What they found was surprising enough to change the conversation about this little muscle.
Muscle Doesn't Just Move Us
We tend to think about muscle in terms of strength.
Can you lift something?
Can you climb the stairs?
Can you get up from a chair?
Those things become increasingly important as we age.
But muscle is also metabolically active tissue.
When a muscle contracts, it requires energy. And where that energy comes from matters.
Many muscles rely substantially on glycogen — glucose that has already been stored inside the muscle.
The soleus can behave differently.
Researchers found that when they kept the soleus working through a carefully developed seated movement, the muscle maintained a remarkably high rate of oxidative metabolism while relying relatively little on its own glycogen stores.
Instead, it was able to make considerable use of fuels circulating in the bloodstream.
Think about what that means for a moment.
There is fuel circulating through the body.
And here is a muscle capable of helping use it — when that muscle receives the signal to work.
The Signal Changes What Happens Next
The researchers developed a movement they called the soleus push-up.
Despite the name, there are no push-ups involved.
The person remains seated with the foot on the floor. The heel rises while the front of the foot remains planted, activating the soleus in a particular pattern. The movement is then repeated for an extended period.
When researchers studied what happened after participants consumed glucose, something remarkable happened.
Post-meal glucose excursions were substantially reduced.
So was the amount of insulin required to manage that glucose.
More recently, researchers tested the technique in a small group of people with prediabetes and again found improved glucose handling while the soleus was being activated.
But here's the part I find most interesting.
The researchers didn't change what those people had consumed.
They changed what the body was doing with it.
That's a very different way of looking at blood sugar.
We Usually Look at What Comes In
When glucose begins creeping upward, most of the conversation naturally focuses on food.
How much sugar are you eating?
How many carbohydrates?
Should you eat less fruit?
Should you stop eating bread?
Those can certainly be relevant questions.
But glucose levels aren't determined only by what enters the bloodstream.
They're also influenced by what happens after it gets there.
Is that glucose being needed?
Are tissues responding appropriately to insulin?
Are muscles actively using fuel?
Or are we spending hour after hour sitting relatively motionless while energy continues to circulate?
Suddenly, the conversation becomes larger than food.
And this is one of the reasons I find this research so interesting. It doesn't suggest that nutrition suddenly doesn't matter. Of course it does.
It simply reminds us that metabolism is not a one-way street.
What comes into the body matters.
But so does what the body is being asked to do with it.
What If Inactivity Is Also the Absence of a Signal?
We often hear that sitting too much isn't good for us.
Usually that gets translated into:
You need more exercise.
Perhaps there's another layer to consider.
What if part of the problem isn't simply that we're failing to burn enough calories?
What if we're also failing to provide certain tissues with the repeated signals they were designed to receive?
Think about how human beings lived for most of our history.
We stood.
We walked.
We squatted.
We carried things.
We shifted our weight.
Our lower legs were constantly making tiny adjustments that we probably never noticed.
Then we created a world in which many of us can sit for hours with our feet planted on the floor and barely move them.
The soleus didn't suddenly lose its metabolic capability.
We changed the environment in which we're asking it to function.
That distinction matters. Because perhaps inactivity isn't simply the absence of exercise.
Perhaps it's also the absence of information.
A muscle that isn't contracting isn't asking for much fuel.
A muscle that begins contracting sends a very different message.
I need energy. And the body responds.
This Isn't About Finding Another Exercise
I don't think the lesson here is that everyone needs to add "soleus push-ups" to an ever-growing list of things we're supposed to do every day.
And I certainly wouldn't interpret this research to mean that a few heel raises somehow erase the effects of a poor diet or replace walking, strength training, or other movement.
The research is still developing, and the dramatic metabolic results came from sustained, specifically performed soleus activity — not simply doing a few random calf raises and expecting blood sugar to plummet.
The larger lesson may be much more useful.
Our muscles aren't merely pieces of machinery that move our skeleton.
They participate in metabolism.
And contraction itself is information.
It tells the body:
I need energy.
That signal changes what happens to the fuel available to us.
Which raises an interesting question.
If our modern lives remove many of the signals the human body once received naturally, how many things we now consider "problems" are at least partly the body's response to a world it wasn't designed to sit still in?
That takes me right back to something I learned years ago with my hands on people's bodies.
The place where we notice a problem doesn't always tell us the whole story.
Sometimes we have to look elsewhere.
Sometimes we have to ask what changed.
And sometimes we have to ask whether something the body expects to happen simply isn't happening anymore.
Maybe the answer isn't always to force the body to behave differently.
Sometimes it may begin with restoring a signal that's gone missing.
Next Week: Blood Sugar Isn't Only About What You Eat
We're going to take this one step further.
Because when we talk about blood sugar, we spend an enormous amount of time talking about how glucose gets into the bloodstream.
There's another side of that equation that deserves just as much attention:
Where is that glucose supposed to go once it gets there?
And what happens when one of its biggest potential users — our muscle tissue — isn't being given much reason to use it?
That's where we'll go next.
Because sometimes understanding what's happening beneath the surface changes the question we need to ask.
Research Behind This Conversation
Hamilton MT, Hamilton DG, Zderic TW. A potent physiological method to magnify and sustain soleus oxidative metabolism improves glucose and lipid regulation. iScience. 2022;25(9):104869.
Gurley K, et al. Soleus push-up exercise and postprandial glucose control in adults with prediabetes. 2025. This small pilot study examined whether the metabolic effect could be reproduced in people with prediabetes outside the highly controlled conditions used in the original research.
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