Thursday, August 9, 2012

Science of the Olympics: Muscles

So we've seen how humans are able to run, swim, and flip about, but why can we even move our muscles in the first place? That is the subject of my final post in this Science of the Olympics series.

The Science of Muscles

Muscles work through a series of contractions. The source of energy for these contractions is a mix of oxygen, glycogen (a carbohydrate), and fat. Those things come together and react to produce ATP (adenosine triphosphate). ATP powers our muscles. 

In other words, fats and carbohydrates react with oxygen to make a substance that helps energy get into our muscles. 

Not actually all too complicated an explanation at first glance. I won't go into the nitty-gritty details that make it more complicated here. Just know that when you move, you can thank ATP.

Anyhow, there are two main types of muscle fibers: fast twitch and slow twitch. What's the difference? Pretty much as it sounds. Fast twitch contracts faster, slow twitch contracts slower. In addition, slow twitch  contracts for longer periods of time than fast twitch. Interestingly, endurance runners (like marathon runners) have more slow twitch fibers than fast twitch. It's not clear if humans can actually change one type of fiber into another, so it may just be that they're born with more of those fibers, giving them the ability to keep their muscles going for longer periods of time. 

Lucky them!

Now, to let any of these muscles fibers work at all, we've got to get them ATP. And to make ATP, we need oxygen. 

How do we get oxygen to our muscles? Our blood of course!

The human heart pumps, on average, five liters of blood per minute at rest. That number increases during exercise. 

The heart pumps your blood in two ways. On one side, it pumps blood out towards your lungs. That blood rushes around outside your lungs, capturing oxygen from your alveoli (lung air sacs). It then takes that back to the heart. This is where the second pump comes in. This time, your heart pumps the fresh, oxygenated blood out towards the rest of your body, instead of just your lungs.

And that's how it gets to your muscles. Now, during exercise, your body tries to optimize blood flow to your muscles. That means it dilates the blood vessels in your muscles (for more blood and oxygen), increases your breathing rate and depth, and diverts blood away from places that don't need it as much (like your digestive track). Olympian bodies are doing this constantly. 

They're also pumping blood out of their hearts much faster than the average person does, and squeezing their hearts harder, too. This gets lots of oxygen to the body, but also means that the lungs have to deal with much bigger "blasts" of blood heading their way each beat. Physically fit people have lungs with blood vessels that can dilate well enough to handle the increase in blood flow safely. People who aren't as fit and try to do something active, resulting in this type of extra-blood-pumping situation, won't have vessels that can handle it. That's what causes high blood pressure.

Finally, physically fit people can take in more oxygen during each breath. Such people have more alveoli available in their lungs, thanks to (safe amounts) of increased blood pressure. That means more places to gather oxygen! More oxygen means more ATP which means more muscle energy. More energy can result in amazing things, like all the broken world records we've already seen at the 2012 Olympics.

So that's the short version of how our muscles work. It's pretty neat to think about all the wacky things that happen in our bodies every instant that we're entirely unaware of, isn't it? Especially when we realize how these little things add up to give us the ability to run, jump, and win gold medals. 

Thanks for following along with me over the past two weeks as we've explored the Science Behind the Olympics! Perhaps there will be a blog series revival in 2014 with Sochi. After all, we've barely skimmed the surface of the science involved in these great games.

No comments:

Post a Comment