How Much Does Genetics Really Affect Your Fitness?
If you don’t see results in the gym, there are many things you can tweak: your diet, exercise schedule, the types of workouts you do, just to name a few. But genetics is also an important factor. We all had this thought on bad days: Maybe I just wasn’t made to do it.
There are genes for aerobic fitness and muscle strength, the ability to adapt to exercise, and the size and shape of your body. To understand how your DNA affects your fitness, we spoke to someone who has thoroughly researched this exact question: Stephen Roth , professor in the Department of Kinesiology at the University of Maryland . The bottom line is this: each of us draws something of our own in the genetic lottery, but we can always improve what we have.
Where genetics plays a role
Don’t worry about whether the trait is determined by “nature or nurture.” Roth says that for any athletic quality, the answer will be both. Scientists look at it differently: what’s the difference between you and other people because of your genes? This is the idea behind a concept called heritability .
Estimates of heritability are always approximate because they depend on the population studied by the researchers. If you only study aerobic fitness in sedentary people, you will find that the difference between the two is mostly related to their DNA. In this case, heritability will be high, close to 100%. But if you include athletes, you see that the big difference between the fittest and the least fit person is training-related, leaving a much smaller percentage – about 50% – that you can blame on genes.
This is why you shouldn’t get too upset about traits with high heritability: something may be extremely heritable, but still subject to change. Obesity, for example, is 70% inherited , which means genes play a big role, but we also know that you can change that through diet and exercise .
Here are some rough estimates of the inheritance of athletic qualities. The higher the heritability, the more you can blame genes, not training, for the difference between a bum and a star athlete.
- Aerobic fitness: about 40-50% is inherited
- Strength and Muscle Mass: About50-60% are inherited.
- Your mix of “slow” and “fast twitch” muscle fibers (mostly whether your muscles are better at endurance or running): about 45% is inherited
- Height: about80% inherited
- Competition in sports: 66% are inherited .
Learning itself alsohas a genetic factor . If you and your partner follow the same program, starting at the same fitness level, one of you may be stronger than the other.
Here’s another complicating but reassuring factor: athletic talent has many components. You may not be able to run as fast as one of your soccer teammates, but you have a better view of where the ball is going and a more powerful shot when you are there. Or maybe you have low cardio endurance, but you have long legs and an effective running stride. So don’t give up, even if you are sure you have multiple unfortunate genes.
How important are genes
Most of us don’t try to compete with world-class athletes, so genetics means less to us than to them.
In a sense, it is easier for us than for the elite, because our bar is lower. Most of us are not trying to win a marathon, but trying to finish – almost anyone can train for this. Or we want our team to beat a rival softball (or hockey, or Quidditch) team where no one has the time or money to train as their regular job. For weekend athletes, improvements can be easily achieved by adding cross-training, attending more training sessions to gain experience and team cohesion, and improving strategy.
The genetic advantage of one elite over another may be tiny, but at the highest level, that tiny advantage could mean the difference between a gold medalist and watching games from home because you finished fifth in the Olympic trials. Elites also benefit from their genetics through exercise, and in that we have something in common. “For amateur athletes, it’s much more likely that training, experience and practice will be the main drivers of performance,” says Roth.
Why is there no simple genetic test
Genetics is difficult. Roth notes that out of 20,000 human genes, only hundreds have been studied and only dozens have been carefully studied for their role in exercise. Just because we know that a gene exists does not mean that we understand how it works or what turns it on.
The main thing we know is that the role of genetics is complex. Take height, for example. In 2009, a study published in the European Journal of Human Genetics showed that you can better predict a person’s height by measuring their parents than by testing and counting 54 genes that are known to affect height.
Thus, even though there are genetic tests for genes associated with fitness, they are not very helpful. One of these genes is called ACE , and some versions of it are associated with aerobic fitness in endurance athletes. The other is ACTN3 , which is related to muscle strength and sprint. There is conflicting evidence as to whether the result of one of these tests matters, Roth said. “This can represent 1–2% of the total productivity,” he says. Based on the results, companies will recommend certain sports as appropriate for you, but “there is simply no science to support this.”
He also discourages doing this testing for children. Since the test results tell very little about what sport a child will be good at, it is unfair to direct them to a particular sport or to push them to compete at a higher level based on a few nucleotides. “If you’re an adult, do it just for fun, have a good time,” he says, “but don’t change your training habits, because the genetic test told you so.
How to determine what you are suitable for
Since the tests won’t tell you much, the best way to determine where your talents lie is by looking at your family and your past experiences.
For example, an adorable baby appears on my Instagram all the time. I’ve never seen him run, but I bet he’ll be super fast when he grows up: his dad is Olympic runner Adam Gusher and his mom is Olympic champion Kara Gusher , who accidentally won a half marathon last week and marathon last month . Kara Gusher’s teammate at the London Olympics, Shalein Flanagan , is the daughter of two elite runners; her mother was once the world record holder for the women’s marathon. You get the idea.
You can also get a great clue about your genetics by trusting your experience. For example, I have struggled with long distance running for years. I showed a fairly average time in races of 5 km (three miles), but was terribly slow over longer distances. I always had a good time for speed work , so I removed marathons from my schedule and focused on short distances. It turns out that I do it better . When I ran the 2K (just over a mile) race, I won a medal as the fastest woman in my age group.
Training programs take weeks to months to show results, so pretty soon you should feel how well this approach works for you. However, do not rush to blame genetics for all your difficulties. Sometimes you need to work harder, but Roth points out that ambitious athletes also tend to overtrain when you struggle because you’re exhausting yourself.
Whatever your genetics, training is never hopeless. For almost all of us, Roth said, productivity “can always be improved.”
Stephen Roth is a professor in the Department of Kinesiology at the University of Maryland, where his research focuses on the interactions between genes and exercise . He is the author of The Genetics Textbook for Exercise Science and Health .
Illustration by Tara Jacoby.
Vitals is a new blog from Lifehacker dedicated to health and fitness. Follow us on Twitter here .