>SEPARATING MARATHON FACT FROM FICTION
Is running a marathon bad for you?
“I think maybe the biggest misconception is that it’s unhealthy,” says U of T’s Greg Wells. Endurance exercise “gets people fitter, reduces the risk of depression, obesity, Type 2 diabetes, cancer, everything.”
That’s not to say there is no risk of injury — or even death — during a race. Studies have discovered adverse biological indicators in runners after marathons, such as higher levels of troponin, a protein associated with cardiac injury, or lower kidney filtration rates. But research shows these return to normal in a couple of weeks, and there is scant or no evidence the body is permanently injured. As for deaths, one study that examined mortality in full and half marathons found 28 deaths out of a total of 3,718,336 race participants over a nine-year period. Your odds of choking to death are much worse (1 in 3,375, according to the U.S. National Safety Council).
Of course, some of the most common ways to die in Canada are from heart disease, stroke and diabetes. “Obviously people do get injured training for a marathon,” says Wells. But “do you want a chronic illness, or a small risk of having knee pain? I’ll take the small risk of knee pain every single time.”
Is “runner’s high” a real thing?
Nearly all runners have experienced the mood-altering effects of a great workout. Most are probably aware that exercise triggers the release of endorphins, molecules that — like morphine and other drugs — act on our brain’s opioid receptors, dulling pain. But researchers believe this is not the whole story of “runner’s high,” in part because the endorphins found in runners’ blood postexercise are too large to cross the blood-brain barrier.
Researchers have also examined the role of endocannabinoids, molecules produced in the body after exercise that, like marijuana, act on a different set of brain receptors. Scientists recently published a paper in the journal Proceedings of the National Academy of Sciences in which they had mice run on a treadmill. Afterward, the mice displayed reduced pain sensitivity and signs of anxiety. They were then given a drug to block certain receptors. Blocking endorphins seemed to have no effect on the animals’ stress or pain, but blocking endocannabinoids did, suggesting the latter plays a stronger role in runner’s high — at least in mice.
How dangerous is dehydration?
In recent years, researchers have been raising the alarm about the opposite problem: illness, and even death, caused by over-drinking in endurance sports. The subject, however, is a matter of intense debate in the field — much of it stirred up by the work of Timothy Noakes, a South African sports scientist and author of the book Waterlogged.
Noakes says that while the medical literature contains no evidence that anyone has ever died from dehydration during a marathon or other endurance event, there have been several cases of athletes dying from hyponatremia — having dangerously low levels of sodium in the blood. Researchers say that over-drinking dilutes sodium levels, and the threat is greatest in smaller individuals and slow finishers (who don’t sweat much but have lots of time to drink). Some also believe the sports drink industry has promoted bad science and suppressed the good. But others believe fears of a conspiracy are overblown, and say the evidence still shows that dehydration affects performance and increases the risk of heat stroke.
Is chocolate milk really the best recovery drink?
If you haven’t actually seen a runner chugging chocolate milk, it’s likely you’ve at least read about it: the beverage has got a lot of press as a post-exercise recovery drink. One scientific study had nine cyclists undertake an interval workout.
They then drank chocolate milk, Gatorade, or a third kind of sports drink, rested for four hours, and climbed back on the bike to cycle to exhaustion. Time to exhaustion was greater for those who drank choco- late milk or Gatorade.
The study — besides being very small — was supported in part by the dairy industry, as has other research on milk and exercise. That doesn’t prove the results are wrong, but it does account for the greater publicity surrounding chocolate milk than for other foods or drinks with the same, or perhaps healthier, nutritional profiles. Chocolate milk’s primary claim to recovery fame is that it boasts a roughly 3:1 carb-to-protein ratio, which helps the muscles store glycogen, an important fuel source in endurance exercise. But a blueberry, banana and peanut butter smoothie could do the same, without the added sugar.