It’s a hazy, summer evening. I’ve got my running duds on and I’ve been pacing the parking lot for the better part of twenty minutes.
Bang! I’m off with the crowd, which quickly drops me behind. After a mile or two, I find my rhythm and start to pass other runners. By the second half of the race, I’m passing more and more people and even seeing a few who have slowed to a walk. I’m the tortoise in a field of hares.
I finish my first half marathon strong, completing my lap on the local high school track and cross the finish line with relief. My time is very, very average, but I feel great. I probably could have run further. Or faster.
And immediately, I want to sign up for another race.
My father looks me up and down and asks, “Are you sure you’re my kid?”
Yep, I’m sure. I’ve got his goofy narrow feet with arches like the one in St. Louis and his tricky left ankle that I’ve sprained by just walking down the street.
So, I start to wonder, what do genes have to do with exercise? Have I somehow overcome my genes to become a person who craves endurance sports? Or did I inherit a trait that my parents don’t have?
Of course this all ties into the nature versus nurture debate as well. Most scientists agree that physical ability is determined by both.
With so many factors at play, how can we know what is responsible for what? Let’s take a look at some fascinating research and what it could mean for your health.
The Basics – Physical Traits
How tall are you? Do you tend to have large muscles, or barely-there muscles (like yours truly)?
Here’s a breakdown of how much your physical traits depend upon your genes — versus other factors such as training and environment. Read the full article here.
- Aerobic fitness: approximately 40-50% heritable
- Strength and muscle mass: approximately 50-60% heritable
- Slow and fast twitch muscle fibers (Think marathon versus 60-yard-dash.): approximately 45% heritable
- Height: approximately 80% heritable
- Competition in sports: 66% heritable
OK, so you’ve got scrawny little muscles or big brawny muscles which you can partially thank your ancestors for. But what else affects how our muscles work?
A transcription factor (a molecule inside the cell that controls our genes) called TFEB was the subject of a notable study at Baylor published last year. When scientists removed the TFEB gene in mice, they had a hard time maintaining exercise. As it turns out, TFEB is involved in how our cells use energy. So with no command station in the mice cells, they couldn’t turn out enough energy to keep running on their little treadmills.
As scientists continue to study TFEB and similar genes, they may be able to identify new drugs to help treat conditions such as diabetes and obesity.
Researchers are also looking at how muscle function may be compromised and what role TFEB might play in regulating our cells and muscles when we are food-deprived.
Run and Done or Go the Distance?
I mentioned earlier that I’m a tortoise; I’m slow and steady, but I can go and go. And go. I’ve entered some shorter races and learned that speed is definitely not my thing.
So, I’m likely missing a particular version of a gene known as ACTN3. Basically, certain variations of this gene protect against damage to muscles and result in more fast-twitch muscle fibers.
If your “sprint” pace is closer to a preschooler putting his shoes on, you probably have a specific combination of genes known as ACE and another gene related to fat-burning – PPARA. What the heck are those?
Specific variations of PPARA result in the ability to switch fuel from carbs to fat during an endurance run, meaning you don’t run out of fuel as quickly.
Even if you happen to be made up of genes that make exercise as easy as making toast in the pouring rain, don’t despair! Sixty-six percent of your athletic ability comes from your genes, which leaves forty-four percent up to you!
Factors like training, motivation, and enjoyment can boost whatever Mother Nature gave you.
Do you come from a family of sprinters, sloths, or somewhere in between? Have you overcome your genes to accomplish great athletic feats? Or benefited from great genes?
Let me know in the comments!
The Sports Gene by David Epstein offers some fascinating answers to these questions. (I tore through this tome in about two days.)