You might think that to benefit from exercise you need to build endurance—to be able to run farther and faster, etc. No doubt, if you put enough effort into it, eventually you could do it, but the question is what are you trying to accomplish? Do you want to win foot races, or are you looking for the metabolic benefits of exercise—losing weight, shrinking your belly and preventing diabetes and heart disease? Running can do this but not because it builds endurance but rather because it restores your muscles’ responsiveness to insulin. When your muscles respond to insulin you need a fraction of the amount you otherwise would to control your blood sugar. Less insulin means less fuel being pushed into your fat cells, particularly in your abdomen.
It’s true that running a couple miles will help keep your insulin levels down. The problem is that most folks don’t have the motivation to do it. Let’s face it, it’s hard. Running makes you tired and short of breath. But here’s the good news: you don’t need to run to restore your muscles’ responsiveness to insulin, lose belly fat and prevent diabetes. You can get the same benefit by walking. Studies repeatedly show that when it comes to losing weight and preventing diabetes and heart disease, walking a couple miles is as good as running the same distance. Here’s why.
Your muscles burn glucose and fat for energy. They also store some to have available for immediate use. If you work your muscles continuously, say 20 minutes, you start tapping into your muscles’ fuel stores. Your muscle cells respond by unlocking the gates on their surface membranes that let in glucose. Insulin is then able to open those gates, and your muscles start responding to insulin.
To get your muscles to start responding to insulin the object of exercise is to deplete their glucose stores. The good news is that you can do that–without making yourself tired and short of breath–by working your muscles but not depriving them of oxygen.
Muscles need fuel and oxygen to do their work. Fuel is not a problem; they can get all they need from the blood. However, if you work your muscles intensely enough they outstrip their oxygen supply. This is when your muscles get tired and you get short of breath.
Here’s how to restore your muscles’ responsiveness to insulin without a lot of huffing and puffing: Exercise your muscles long enough to deplete their fuel stores but not so intensely that they exceed their oxygen supply. You can do that by walking about 25 minutes. You don’t need to run. That’s why the Surgeon General says to walk 30 minutes five days a week.
What Are You Building When You Build Endurance?
Your muscles get oxygen from the blood. Your ability to run farther faster has nothing to do with muscle strength or lung capacity. It’s a matter of how much blood your heart can pump to your muscles–your “cardiac output.” This is determined by a) how fast your heart can beat and b) how much blood it can pump with each beat.
How fast your heart can beat is purely a matter of age. The older you are, the slower it beats at maximal exertion. It doesn’t matter how good of shape you’re in; you can’t change this. What changes when you build endurance is how much blood your heart can pump with each beat. The more blood it can pump with each beat, the better your endurance.
The amount of blood your heart can pump with each beat is actually not a matter of how strong your heart muscle is. Rather, it depends on how well it relaxes between beats. Your heart has to open up between beats to let blood flow into it. At maximal exertion it has only about one sixth of a second to do that. Ironically, when you build endurance you don’t build strength; you promote relaxation–of your heart.
Bottom line: You don’t need to run, i.e., build endurance, to eliminate hyperinsulinemia. All you need to do is walk. It’s a lot easier. Some might even call it pleasant.
