Which Comes First, Cardio or Weights_ - Alex Hutchinson [10]
Translating the definition of “moderate” exercise from mice to humans is a challenge. Certainly, those following standard exercise guidelines (for example, half an hour of moderate to vigourous exercise five times a week) are bolstering their defences against infection. In fact, in a study of 2,300 runners training for the Los Angeles Marathon, only those training more than 60 miles per week had an elevated risk of catching a cold. “If I’m swimming in the morning then running at night, or doing a marathon, that’s where you’re going to see a dip in immune function,” Timmons says.
Interestingly, the immune-boosting benefits of exercise seem to show up almost instantly. Another mouse study by researchers at Iowa State University, published in 2009, compared the effects of a 14-week moderate exercise program with the effects of a single 45-minute treadmill run done just 15 minutes before being infected with the flu virus. As expected, the habitual exercisers fared best over the following 10 days, showing the greatest reduction in symptoms and virus load. But surprisingly, the mice that had done just one run still fared significantly better than the sedentary controls, although the benefits faded after a few days. This is worth bearing in mind next time you’re headed for a high-infection-risk zone like an airplane: working out the day before or even the morning of the flight could help you ward off bugs.
Human studies have found similar results. For example, a year-long University of South Carolina study of 547 adults found that those who exercised moderately caught 20 percent fewer upper respiratory tract infections, with the biggest benefit at the start of cold and flu season in the fall. Other epidemiological studies have made similar observations. So if you’re hoping to stay healthy over the winter, the evidence suggests that you’ll get more benefit from hitting the gym than from stocking up on orange juice.
Is motivation to exercise genetic?
When Colorado-based Atlas Sports Genetics started offering its “SportsGene” test in 2008, zealous parents rushed to uncover their children’s athletic destiny. “The results have helped us immensely,” one Texas mom wrote in a testimonial. “We have changed his extracurricular activities to be more in line with the test results.” Atlas offers a $169 test of the ACTN3 gene, which, according to an Australian study from 2003, can indicate whether you’re best suited to endurance sports, sprint and power sports, or a mix of the two. Whether or not the test imparts useful information—which is still very much up for debate—you probably shouldn’t choose how your two-year-old spends his or her playtime based on dreams of future athletic glory. But it’s impossible to deny that your genes do play a role in your athletic destiny.
According to a 2006 study of over 85,000 twins in seven countries, about 62 percent of the variation in exercise participation seems to be inherited. This could be because of personality traits that run in families—people who are self-disciplined tend to exercise more, while those who are anxious or depressed exercise less—or physiological differences such as the production of feel-good dopamine after vigorous exercise. The genetic tendency to lose weight or gain muscle could also make some people more likely to exercise than others.
All of this suggests a certain inevitability: either you were born to exercise or you weren’t. But in the years since that study, something interesting has happened: the search for the “exercise gene” has run aground. Several studies have analyzed the DNA of thousands of people, looking for the sequences that predict exercise behavior—and they’ve found not one but many. A 2009 study of 2,600 Dutch and American adults found 37 different DNA regions that were linked to exercise, and these regions were entirely different from the dozens of regions identified in previous studies. In other words, there isn’t an exercise gene—there are hundreds of different genes that combine to influence every aspect of