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Genes only tell one part of the story – diet and how much effort individuals put into exercise also play a role.

Michelle Siu/The Globe and Mail

Do we really need a test to tell us whether our genes are sabotaging our efforts to get fit?

A burgeoning industry is being built on the promise that genetic tests can predict how individuals are likely to respond to exercise and at which types of physical activity they may do best, an alluring concept for those who have struggled to get fit for years and never seem to see the same results as others.

As scientists gain a better understanding of genes, companies specializing in exercise-related genetic tests are cropping up. XRGenomics is one of the newest in the field. The company developed a test designed to look at a person's genes to predict whether they can easily improve their VO2 max, or their capacity for aerobic exercise. Simply put, the higher your VO2 max, the longer and harder you can exercise.

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The company says its test, available through its website, is different from many of its competitors, particularly because it is based on clinical research and it looks at a higher number of genes.

The test focuses on genes linked to the body's maximum capacity to carry oxygen to muscles during exercise. It can give people useful, accurate information to help them improve their physical health, says James Timmons, the company's director and a professor of systems biology at Loughborough University in Britain.

The genetic test is suited for everyone, Timmons said, whether physically fit or not. "We see it as potentially a motivation tool for both ends of the spectrum," he said.

Even so, the idea raises numerous questions about how valuable such information is and whether the results are as empowering as proponents claim.

The XRGenomics test is designed to detect genetic patterns that make some individuals "low responders" to exercise. In other words, it can spot individuals who have a difficult time improving their aerobic capacity. About 20 per cent of the population falls into that category, according to Timmons. That means 80 per cent of people don't face any particular challenge if they want to increase their ability to exercise.

Even if people are considered "low responders" under the XRGenomics test, they can still improve their VO2 max levels through working out. They'll finish the race, even if they won't bring home a medal.

And genes only tell one part of the story. While they may be a big component, many other factors are at play that help determine aerobic capacity, such as diet and how much effort individuals put into exercise.

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The entire concept of genetic testing is irrelevant, according to Arya Sharma, professor of medicine and chair of obesity research and management at the University of Alberta, because exercise is good for everyone, regardless of ability or capacity. Physical activity is linked to countless health benefits, including a lowered risk of high blood pressure, heart disease and certain types of cancer.

Unless you're considering a career as an elite athlete, does it matter if a test tells you that your natural ability for aerobic activity is relatively low? And considering only 20 per cent of people fall into that category, how does genetic testing help the rest of the population?

Timmons describes the XRGenomics testing as empowering, allowing people to focus on exercise that is geared to their strengths.

But Timothy Caulfield, Canada Research Chair in health law and policy at the University of Alberta, sees it as an overly simplistic solution to a complex issue. He highlighted the case of the "sprint gene." Researchers have identified a genetic variant that gives some individuals an extra boost to their "fast twitch" muscle fibres, arguably enabling them to excel in activities such as sprinting. But plenty of elite-level sprinters don't have the genetic variant, Caulfield points out.

"I think that there's absolutely no doubt that how we react to exercise has a genetic component to it, just like everything in our lives," he said. "But how they play out … history tells us again and again, [is] much more complicated than initially anticipated."

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