#431 The Second Most Important Muscle In Your Body and How to Train It - Marc Hamilton PhD

Marc Hamilton (0:00)

The key features is that we learned how this muscle, the soleus, can use about 300% of the energy level that it would be using if you were exercising on a treadmill, for example, if you were jogging on a treadmill. So it means that this muscle can use much more energy with this specific movement called the soleus push-off than if you were standing or walking or even running on a treadmill.

Siim Land (0:25)

Welcome to the Siim Land Podcast. Our guest today is Dr. Marc Hamilton. Dr. Hamilton is a professor of biology and biochemistry at the University of Houston. He's the creator of the exercise called the soleus push-up. The soleus is a special type of muscle underneath your calf muscles that Marc and his team discovered to have a unique effect on the metabolism. In a 2022 study by Marc and colleagues, they found that stimulating the soleus muscle with the soleus push-up while sitting for several hours was able to lower the blood sugar levels to an oral glucose challenge by 52%. The interesting thing about the soleus muscle is that it's infatigable, which means that you can stimulate it for several hours every day without getting tired. It essentially looks like a seed at calf raise, but there are some nuances to doing it correctly, which we will all discuss in this episode. Marc is very passionate and scientific about this topic, so he likes to explain this very thoroughly. But I promise to you, if you listen to this until the end, you'll have several epiphany moments when it comes to exercise, walking, and a mighty soleus.

Dr. Hamilton, welcome to the show.

Marc Hamilton (1:24)

It's nice to be here. Thank you for inviting me.

Siim Land (1:27)

Yeah, I'm excited to have you on the show. And the reason I wanted to invite you was you published this kind of really exciting and almost like groundbreaking study a few years ago about the soleus muscle and how it has kind of an interesting effect on glucose metabolism and just overall health. So yeah, I'm like really keen to like go into all the details of that muscle. So maybe we can start with you giving like a brief overview of yeah, what did you find in the study and how did you like conduct it?

Marc Hamilton (2:01)

Well, I think that the main point, first of all, is not even what we found in this one specific study. I mean, there's a number of studies that we conduct that deal with this general topic. And I think that the first, the big news was really in being able to understand that the human soleus muscle has inherent properties that if used the correct way, can have some outsize effects on the body. So you think about the fact that the soleus weighs about a kilogram, roughly 1 percent of the body weight is able to have these outsize defects on the rest of the whole body. And that was unexpected.

And frankly, it wasn't even the initial purpose of our research. And so I'll be glad to discuss that with you. But it was, the paper that you've read was downstream of several other lines of research that my lab had been doing, that where we could test this hypothesis, that soleus contractions by themselves could have quite meaningful effects on the body in numerous ways. And you are right, you pointed out that one of those is improving glucose tolerance.

Siim Land (3:20)

Right. And I, as I recall, then the effect was pretty big in those people who were training it.

Marc Hamilton (3:28)

That's right. And so the particular study you're looking at was with the immediate benefits of soleus contractions. So when people think about muscle metabolism, one of the most important principles is something that remarkably is almost never discussed. And it's not a controversial thing.

It's just a simple fact of nature, which is that muscle metabolism at rest is relatively low, meaning that a kilogram of muscle has an imperceptible effect on your whole body, caloric expenditure, or glucose utilization, fat use, and even the entire body's muscle mass, which is, you know, muscle can be the largest tissue in the body. But because each kilogram of muscle has a very low metabolic rate, its contribution to total body metabolism is somewhat attenuated by that. So if you think about muscle, think about it like a machine, and a machine needs fuel. And when the machine is not running, it's not working, it's going to use very little fuel compared to when it's working. And other tissues aren't so much that way. The brain, for example, is always using a lot of energy, even when you're asleep, its process is doing things. The heart's pumping 24-7. The kidneys are always filtering and working. But skeletal muscle is unique in that humans have voluntary control over the metabolic rate of muscle by what you're doing. And what we said was that a fundamental problem currently, and when I say currently, I mean in the last 50 years, in humans is that we sit a lot, and when we sit, our muscles are inactive.