Fitness, by the Genes

Many people notice that they dutifully take the same gym class as a friend or run the same number of miles as a spouse, yet end up with drastically different results. That gut feeling is being increasingly backed up by the newest research by exercise scientists who agree that athletic potential is at least partially hardwired into our bodies through inborn traits like aerobic capacity and a tendency to excel at either power or endurance activities. It turns out an individual’s variable response to training may be partially determined by genetics.

And that’s also why a growing number of direct-to-consumer fitness DNA tests are being used by serious athletes and casual exercisers alike. For instance, saliva tests that offer a purported customized exercise profile. Tests like these can pinpoint a personalized fitness plan, one that delivers results like lower disease risks or superior training gains. The manufacturers claim these tests can benefit clients in maximizing athletic potential or simply getting healthier.

But experts disagree on how much an individual’s fitness potential is truly pre-determined and the research into these DNA markers is still emerging. Dr. Robert Otto, professor of exercise science and health studies at Adelphi University, is somewhat skeptical about the trend. “I think the testing should go through an intermediary, an expert like a doctor or a trainer who can interpret the information,” Otto said. Like him, many in the medical field worry laypeople may not know how to apply the results. Otto said the technology is promising, and is likely the future of exercise science, but he’s not convinced the current research can offer helpful information beyond what can be found through trial and error or existing muscle fiber testing.

The Tests
DNAFit is a UK-based company whose slogan “Train Smarter, Not Harder” could serve as a good catchphrase for the entire genetic fitness testing industry. Most people will try to do the least amount of exercise necessary to meet their goals, whether that’s disease prevention or weight loss, but access to sophisticated training plans or coaches is often lacking. Keith Grimaldi, the company’s chief scientific officer, learned his ideal training routine the old-fashioned way—through years of trial and error as a long distance runner. He said DNAFit would have circumvented that long process.

The basic fitness test (about $200) looks at 20 genes to determine power and endurance potential, post-exercise recovery speed, injury risk profile and recovery nutrition needs. A premium exam (about $250) adds on aerobic (VO2 max) potential, a full genotype report and breakdown and a DNA benchmark against a roster of British Olympic track-and-field athletes.

The mail-order kit contains cheek swabs that users mail back. Two weeks later a report comes via email listing results for each gene tested, any propensity for overtraining injuries, potential recovery times and training recommendations. The data in that report comes from 12 years of DNA testing of elite athletes, but Grimaldi is certain that it can also yield valuable results for recreational gym-goers. For instance, knowing one’s susceptibility to soft tissue injury would go a long way in determining the ideal frequency and intensity of a weekly workout plan.

Even seasoned athletes have been surprised by some of their genetic results. Grimaldi recalled how a professional soccer player discovered he had more of a power profile rather than endurance and adjusted his training to maximize genetic strengths like sprinting and explosive moves. There are over a dozen genes associated with either talent in power sports (sprinting, weightlifting) or endurance (long distance running). By examining the international literature and sifting through research done on athletic populations, DNAFit was able to create a test that can identify the most productive categories. “The most important part of the results is how to personalize a training program,” Grimaldi said. “Adding the genetic information gives trainers more information and takes some of the guesswork out of it.”

The research on DNA markers is ongoing and more specific indicators are being mapped out. Grimaldi cautioned that there is not currently enough evidence for any kind of sports eugenics (that would predict future talent). His best guess for how much the inherited markers affect real world performance is anywhere between 30 to 70 percent. For VO2 max, which measures the maximum uptake of oxygen that determines aerobic output, it’s considered to be about 50 percent.

Harder to study factors like cultural, familial, personality and economic differences make up the other pieces of the pie. But one of the more practical applications of the test is it keeps exercisers exercising, Grimaldi said. People are more likely to stick to what works. If someone is predisposed for power and carries DNA markers for a tendency to get inflammation and tendonitis with heavy training, yet they keep trying to run a faster marathon, they can use the results to prevent working against the genetic tide.

The outcome of the DNAFit test for Charles Wallace, a fitness writer for The Financial Times, was in line with his experience as a lifelong runner. But the results of the exam’s diet portion were surprising. Wallace learned he has a genetic variation associated with bone loss from excessive caffeine intake, which confirmed his suspicion that he was sensitive to carbohydrates. Wallace switched to decaf and found it to be useful.

“The nutritional information was enlightening,” he said, though the fitness results didn’t offer him any actionable news. His strength versus endurance testing showed he was equally predisposed to both, but since he already divides his time between strength and endurance training, those results didn’t spur him to change his routine.

While DNAFit provides data about one’s ideal types and amounts of exercise, UK-based XRGenomics offers a test that looks at a person’s likely response to exercise in general. The company, and its approximately $250 XRPredict+ kit, was launched after its lead scientist participated in a BBC documentary on the research behind individual response to exercise.

Results showed that there are three broad categories of people: Low, medium and high responders. If all three groups performed the exact same training, the results differed wildly. Dr. Jamie Timmons is a biology professor and XRGenomics’ co-founder and chief researcher. He said after the documentary aired he was bombarded with hundreds of people asking him for personalized advice. He tried to answer individual emails for months before starting XRGenomics and deciding to make a publicly available test. With each kit comes a detailed questionnaire for the user to return, along with samples swabbed from a cheek. About a month later, XRGenomics produces an 18-page personalized training plan.

The method, he said, was a novel approach produced in their laboratory, which involved seven years of tracking down genes related to fitness response. Timmons thinks that for the vast majority of adults who are interested in an overall healthy lifestyle, finding out the best parameters to measure fitness gains is crucial. Not everyone will see improvements in performance with aerobic exercise and so the test advises them to focus on different goals, like achieving a lower resting heart rate or correcting cholesterol levels. Even if a client finds s/he is in the low responder category, there is still benefit in making smarter health choices that don’t include aerobic exercise. In fact, there is even a small percentage of the low responder group—2 to 4 percent—who actually demonstrates a negative training response to average amounts of exercise. But low responders can adjust goals and measurements to help with motivation. “If you don’t think you’re improving, you will be less likely to continue,” he said.

Timmons thinks this is just the beginning and predicts the information will become more specific and sophisticated over the next few years. And it’s not just exercise that is affected by genetic blueprint. Domestically, Inherent Health offers nutrition and weight loss genetic information. Their Weight Management test ($170), screens for DNA markers for fat loss and fat stores. The company claims that finding out one’s genotype can help with a personalized nutrition plan—some people react better and lose more weight on a low carbohydrate diet than a low fat one, for instance.

Pathway Genomics is a San Diego-based company that also focuses on the nutrition and weight management gene component, along with some of the same fitness measurements covered by the DNAFit test. Their Pathway Fit test, available through health-care providers, determines risks of obesity, weight loss and gain, eating behaviors, feelings of satiety and associations with food intolerances and deficiencies.

While genetics may not be destiny, information is always power. And in the case of finding out a personalized, best exercise blueprint, sending some cheek cells through the mail might mean a crack in the case for the healthiest you.

Jacqueline Sweet

Jacqueline Sweet

Jacqueline Sweet is a freelance journalist and writer who covers local news and writes features for local and regional publications. She has published work in national magazines like Salute magazine, Family (military) magazine, Triathlete magazine, regional publications like Long Island Pulse and Long Island Parenting, and reported local news for online outlets like and She has been covering health, wellness, fitness beauty, spa and travel for Long Island Pulse for several years.