It seems like some people are just born to be good at certain sports. They’re the perfect height or they have the right physique or they’re so much faster than most people. To us, their skills appear to be effortless — or, at the very least, their bodies respond better or faster to training compared to others. It turns out that there’s a kernel of truth to the idea because genetics and athletic performance are related.
Does genetics predict athletic performance? The answer is a firm no. But thanks to a relatively new area of genetic research, scientists are beginning to uncover the connections between DNA and physical traits. DNA can increase or decrease the odds that certain people will excel at various types of athletic activities more than others — so, being “born with it” isn’t a total fantasy.
As DNA testing has evolved to include genomes from healthy people, it is inspiring scores of studies focusing on how DNA influences lung, muscle, and cardiovascular function. Wider data pools, along with technology that’s advanced enough to support larger studies, are allowing us to approach the science behind athleticism in exciting new ways.
One area of interest has revolved around endurance versus strength. Humans have two kinds of muscle tissue: slow twitch and fast twitch. Slow-twitch muscle function relies on oxygen (meaning it’s aerobic), which makes it able to sustain activity longer and leads to greater endurance in people who run marathons, for example.
On the other hand, we have fast-twitch muscles which, like the name suggests, create contractions that are more powerful and can reach peak force in less time than slow-twitch muscles. They activate only when slow-twitch muscle fiber can’t meet the needs of the force required, and these muscles are what weight lifters and sprinters rely on. The downside to this type of muscle fiber is that it uses up energy faster and therefore needs more time to recover.
One of the most widely studied genes associated with athletic performance is ACTN3, also known as the “sprinter’s” or “speed” gene. This particular gene has instructions that produce alpha-actinin-3, a protein that helps fast-twitch muscles contract powerfully at high speeds. People who produce more alpha-actinin-3 are predisposed to be more adapted to sprinting instead of long-distance running. However, if you have a specific variant of this gene, your fast-twitch muscle fibers will behave more like slow-twitch muscle fibers — which explains why this variant is more often found in endurance athletes.
Another significant discovery is the role of genetic variants related to muscle strength. Researchers have discovered 16 different variants that play a role in grip strength. One of the influential genes was TGFA, also known as transforming growth factor alpha. TGFA is known to play a role in cell division and encouraging the growth of new blood vessels. The variant in this gene is associated with about half a pound of increased grip strength. While it might not sound like anything substantial, start adding up the effects for all 16 variants and you start to see that genetics can have a real influence.
Even though DNA testing can reveal certain predispositions, they should not be thought of as predictors of actual athletic ability. Your athletic performance is directly impacted by a host of other factors that you have degrees of control over. Things like environment, diet, training, skill level, work ethic, and enthusiasm can play a huge role in your fitness levels. What your DNA says about you works in tandem with how you approach your fitness regimen — and no one factor is more important than the other.
For example, let’s say you have the ACTN3 R577X variant, which predisposes your muscles to behave like a slow twitch muscle. This doesn’t mean you can’t become a powerlifter. What it does mean is that you may need to work harder, compared to someone without the variant. But if this sort of training is something you enjoy, and you tailor your diet and workout regimen to help you meet your goals, there’s nothing — including your DNA — that says you can’t achieve them. For example, in the 2008 Olympics, an athlete with the ACTN3 variant (the one that suggests you may not be well suited for sprint sports) won a Bronze in the 4 x 400m relay event. Even though he found out he had the endurance variant, he didn’t let his DNA dictate what he could or couldn’t do.
What DNA testing can do is give you insights to help you make more informed decisions on your approach to fitness training. If you struggle as a sprinter, it could be that your body is better suited for an endurance sport and perhaps you could give swimming a try. Or if you’re wanting to try something new, your DNA might be able to suggest something you’ll enjoy. The important point to remember is that it is, ultimately, your choice.
DNA insights can help us make meaningful shifts in how we challenge ourselves, how we eat, and how we approach rest and recuperation. It may also help us avoid injury, as the genomics community studies the links between certain genes and susceptibility to injuries like stress fractures. And though our genes can’t possibly explain everything, they can certainly help us support us in our quest for better health and athletic performance.
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