If you're serious about fitness, you know the importance of training your muscles and your brain. Without the right prep, you won't have the physical or mental endurance to finish, whether it's a five-k or an Ironman. But it turns out that it may be just as important to train your gut—or suffer inflammatory consequences. So says a study in the International Journal of Sports Medicine. [Gill SK et al, The Impact of a 24-h Ultra-Marathon on Circulatory Endotoxin and Cytokine Profile]

Researchers sampled the blood of 17 runners before and after a 24-hour ultramarathon—where runners covered anywhere from 75 to 130 miles on foot. During the race, their guts got leaky—due to a lack of blood flow to the intestines, and the physical trauma from so many jarring miles. Gut bacteria escaped into the blood, where some released toxins. The runners' bodies then responded by launching an immune response, and inflammation set in.

Some runners actually had blood profiles identical to those of patients admitted to the hospital with blood poisoning, or sepsis.

But the most well-trained competitors avoided the problem. Their bodies launched a counterattack, unleashing anti-inflammatory compounds to tamp down their bodies' immune overreaction.

The authors say just four hours of activity is extreme enough to kick off this chain of inflammation. Suggesting it's key to gradually build up to new personal bests, even if they're not ultraworthy. As has long been said: slow and steady wins the race.

—Christopher Intagliata

[The above text is a transcript of this podcast.]