Why do the runners look flushed only 20 minutes into the race?

The runners likely look flushed just 20 minutes into the race due to increased blood flow to the skin, which helps regulate body temperature as they exert themselves. This physiological response, combined with elevated heart rates and physical exertion, can cause visible signs of flushing. Additionally, factors like hydration levels, ambient temperature, and individual fitness levels may also contribute to their flushed appearance.