Running in the Heat: A Look at Cytokine Levels and Body Temperature

Ever wondered what happens to your body when you run a 7-mile race in warm weather? Seventy-seven recreational runners found out the hard way during a recent race where the temperature ranged from 25. 0 to 26. 7°C and the humidity was between 56. 7% to 79. 0%. Before and after the race, their blood was checked for inflammatory cytokines, and their core body temperature was monitored using a special thermometer they swallowed. Guess what? Their core temperature shot up from an average of 36. 9°C before the race to a toasty 39. 5°C after. That's a big jump! And it's not just their temperature that increased. The levels of three key cytokines—IL-6, IL-8, and IL-10—also went up. For instance, IL-6 levels jumped from 28. 4 pg/mL before the race to 48. 0 pg/mL after. But here's where it gets interesting. The bigger your increase in core temperature, the faster you likely finished the race, and the more you lost in body mass. Also, higher levels of IL-6 were linked to bigger increases in core temperature. There was even a small connection between IL-8 levels and core temperature after the race. So, in simple terms, running in the heat can really heat you up and boost certain chemicals in your blood. And if you finish fast and lose a lot of weight (which isn't good, by the way), your body gets even hotter.