Over a month ago, I was on Instagram when I saw a video of a scientist who said, “They put the blood of people exercising on cancer cells, and the cancer cells died.”

By now, we already know that exercise is crucial for optimal health, but this angle, that the blood of people who exercise may be able to kill cancer cells, will definitely be strange to most of us.

Exercise-conditioned serum refers to blood serum collected from an individual immediately after a bout of physical exercise.

When a person exercises, their muscles, organs, and immune system secrete bioactive molecules into the bloodstream. Blood taken immediately after acute, moderate-to-high-intensity exercise is rich in these mobilised molecules.

In research settings, scientists separate the serum from this post-exercise blood and use it to culture cells in a laboratory (an in vitro environment).