Science Friday: Oxidative Stress is Hot Stuff

In last week’s post, I discussed hot weather training and how its benefits persist even in cold weather; since your body has to work harder in the heat, you are forcing it to toughen up. This translates to improvements that last even when the stimulus is gone. (The same way training at altitude pays off at sea level.)

This week, I came across a study that discusses one of the ways this may occur, i.e. one of the ways heat forces lasting improvements. Here, subjects biked for an hour in different temperatures: 45° (cold), 68° (room temperature), or 91° (called “warm,” but this warm-weather wuss would call that “hot”). Afterwards, the subjects were kept in their temperature-controlled rooms for three hours. (It’s unclear what they were doing for those three hours. They were given dry clothes, something to drink, and got to lay down, which sounds like a perfect recipe for a post-workout nap, but they were periodically poked and prodded by the researchers, so maybe not.) Blood samples obtained over the three hours were examined for markers of oxidative stress. When oxygen is broken down by mitochondria to produce energy (as happens normally and to an increased extent during exercise), reactive oxygen species are also produced in the process. Oxidative stress occurs with the overproduction of these species, which are thought to damage DNA and accelerate aging and disease. (This is why people tout antioxidants, which sop up these species.) In the study, the subjects that exercised and recovered in the warm room had the highest levels of oxidative stress.

But oxidative stress is not necessarily a bad thing. Like weight lifting or running, it causes a stress to your muscles that forces them to rebuild stronger. In this case, oxidative stress encourages cells to make their own antioxidants and increase mitochondria, which make all that wonderful energy. This increase in oxidative stress in the heat may be one of the explanations for the benefits discussed last week. Just like heat demands us to deal with less blood pumping to our muscles, it also forces us to deal with reactive oxygen species. The muscles clean up the mess and patch us back up, better than ever.

I wished the experiment had also examined differences between exercising and recovering in the heat. (A way to test this would have involved everyone first exercising in the heat, followed by half the subjects recovering at room temperature and the other half recovering in a hot room.) Recently, there have been warnings against going overboard on recovery aids. In some regards, the soreness, inflammation, and—in this case—oxidative species caused by a run are a good thing. Ice baths, ibuprofen, or perhaps even cooling off in a comfortable room may cut your body too much slack. The researchers didn’t test that here, but it’s an interesting idea.

Antioxidant supplements have come under fire recently for a similar reason. As I described in a post about vitamin C, taking antioxidant supplements (which contain a much higher dose than found naturally in fruits and vegetables) may block our bodies’ adaptations to exercise. (An interesting take on why fruits and vegetables are better than synthesized pills is here.) Again, it’s a case of overdosing on recovery; trying to force your body to bounce back, when the best improvements are made by letting your body recover naturally, with whole foods, time, and perhaps even a post-run nap in a warm spot.

Dream big,
Teal