Throwback Thursday: Build Thee a Capillary! How exercise upgrades your body in ways we can’t even see.

Slightly scary news this week from Every48 world: a very close family relative had a very mild stroke last week, and was slightly miffed because she’s done a whole lot to improve her health in the last few years, including losing 50 pounds.

So, a stroke? What? This was a head-scratcher for her, because she thought she was “healthy” because she was losing weight.

It's really not a head-scratcher. Regular exercise improves your circulatory system. (Image courtesy of David Castillo Dominici at
It’s really not a head-scratcher. Regular exercise improves your circulatory system. (Image courtesy of David Castillo Dominici at

But, ahem, she sits on the couch. All. Day. Long. Every day. Classic sedentary lifestyle. So, guess what her doctors told her?

They simply said that one of the risk factors for blood clots is inactivity. (That’s why you want to get up and walk around on a long airplane flight.) This is news she can use. She’s already promised me she’s going to try walking for 10 minutes at a time, three times a day. Because you know what? That little medical scare freaked the living daylights out of her – and I’m kind of glad it did, because this is important, life-saving stuff.

Yet another reason to have an active lifestyle: Your circulatory system likes it.

[Want more deets? Here’s a solid research paper on the correlation between inactivity and stroke risk, if you’d like to delve more deeply into the subject.]

So in that spirit, for today’s Throwback Thursday, I bring you one of the original Every48 posts that got the ball rolling all the way back in February 2014: “Build Thee a Capillary!” It’s all about how exercise can literally change your circulatory system from the inside out. (In other words, it’s not just about the flat abs.)

Build Thee a Capillary!

[First published on February 11, 2014]

This is your body on exercise - from the inside out. More capillaries equals more circulation equals a better-working body, all around.
This is your body on exercise – from the inside out. More capillaries equals more circulation equals a better-working body, all around.

Here’s some news you can use: exercise doesn’t just keep your weight down or make you look trim or give you sleek muscles. It upgrades your body from the inside out. Every minute of exercise you give your body starts a serious conversation between your muscles, heart, skeletal system and all of the internal systems that make our bodies “go.”

I sort-of knew this from high school biology class but somehow missed the memo in my twenties and early thirties about exercise doing more for us than just creating cosmetic changes that other people could see. As I’ve walked down the path of becoming a chronic exerciser (gosh, I love that term), I’ve begun to appreciate something. Exercise doesn’t just give us a more finely-tuned version of whatever body we got when we got assigned bodies on this planet. It can cause a serious upgrade.

Yes, Ferrari. I want to be just like you.
Yes, Ferrari. I want to be just like you.

In other words, if you think of your body as a car that needs regular maintenance and gas,  and you think got a Toyota Corolla – trusty, not too sexy, but definitely can go the distance as long as you take care of it – then regular exercise that pushes you further and challenges you can turn that body into a Ferrari. Welcome to Science Week, Day 2 at Every48.

Exercise builds new capillaries.

It really does. It builds and strengthens the highways that transport the stuff our bodies need to survive and thrive. Here’s a little more info:

Capillaries are the smallest blood vessels in the body, connecting the smallest arteries to the smallest veins. Capillaries have very thin walls, allowing oxygen and nutrients to pass from the blood into the tissues.

– From

Now, what does exercise do to these here capillaries? Check this out, from the paper “Muscle Adaptations to Aerobic Training” by Ronald L. Terjung, Ph.D. (The bold print is mine, for the big takeaways.)

“Exercise training increases the number of capillaries surrounding individual muscle fibers. In effect, when a fiber is recruited it becomes more effectively ‘bathed’ in the flow of blood delivered to the muscle. Although the increased capillarity is most easily observed in the low-oxidative (type IIb) fiber regions where the capillary density is normally the least, this development of new capillaries can occur in all fiber types (Saltin & Gollnick, 1983; Yang et al., 1994). An increase in the number of capillaries surrounding each fiber should improve the oxygen exchange between capillary and fiber by presenting a greater surface area for the diffusion of oxygen, by shortening the average distance required for oxygen to diffuse into the muscle, and/or by increasing the length of time for diffusion to occur (i.e., the red blood cell spends more time in the capillary). These effects of increased capillarity would contribute to the increased oxygen extraction that occurs in trained muscles of laboratory animals (Bebout et al., 1993; Yang et al., 1994) and human beings (Saltin et al., 1976) and account, in part, for the increase in whole body maximal oxygen consumption that is observed in endurance trained individuals.”

In other words, exercise is really, really good for your capillaries. (By the way, that paper was written 19 years ago. We’ve known this stuff for a while. I’m just sayin’.)

Big Word Alert: Angiogenesis

Whoa, that is a seriously big word. And it's what happens when we exercise. We literally build new stuff inside our bodies.
Whoa, that is a seriously big word. And it’s what happens when we exercise. We literally build new stuff inside our bodies.

I’m going to keep on researching this stuff this week, but here’s a previous of coming attractions. Angiogenesis is “the physiological process through which new blood vessels form from pre-existing vessels.” It happens for various reasons, not all of them good (it’s how cancer tumors grow, for example) – but the relationship between aerobic exercise and angiogenesis is pretty fascinating. If you’d like to read more, check out the paper “What makes vessels grow with exercise training?” in the Journal of Applied Physiology. Really fascinating stuff.

So, the next time you want to sit home and channel-surf, and you don’t feel like getting your workout on, how about some self-talk that goes like this? “Come on, you can do it – you definitely need to work on building some new capillaries.”

And one more thing.

There’s a reason I’m jumping into the science behind this stuff, in a pretty heavy-duty way.

When I realized my health story was not going in a positive direction – mid-thirties, forty pounds overweight, blood pressure teasing the “stage 1 hypertension” range, no energy, and all of the other extra bonus prizes you get for living life that way, like being down on yourself all the time – I needed to know my body could become a predictable entity. A machine, as it were. I could see it as a pile of problems – bad genetics (ha ha), a “slow metabolism” (there’s no such thing – I was just eating too much, and the wrong things) – whatever. I could think I didn’t win the genetic lottery so, woe is me. (That’s why I wrote the post on what to do if you wish you were Russell Wilson, by the way. It’s so, so easy to be envious of people who appear to have something you think you want and you think you will never have. It gets in the way of doing what we have control over to change our own lives.)

So, when we get into the science behind this stuff, we figure out that we’re all pretty much the same on the inside. And that means that taking care of ourselves – regular exercise, good nutrition, regular sleep, work that we love, and people we love around us – is going to affect the machine very, very positively. I consider myself today to be a scientific experiment of one, because I had to take these findings and translate them into things that would work well for me.

And, what was the measurable external result of all of this experimentation, you ask? Tune in tomorrow for the triumphant conclusion to the adventures in capillary construction I experienced in my own life when I really gave exercise a solid shot.

And back to real time – August 28, 2014:

Yesterday’s #Every48 workout: A wonderful TRACK workout with my running tribe. Mostly running this time, a little walking, 5.98 miles total (thank you Garmin GPS for the two-decimal precision). Knee feels great! Here we go.

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