Most people would do everything possible to avoid getting zapped by an electric eel. But lately, Kenneth Catania, a biologist at Vanderbilt University, has been willingly tempting one of these creatures to strike him.

Catania is not crazy, nor is he filming some newfangled reality TV show. In fact, he’s been offering up his own arm to the eels in the name of solving a math equation.

You see, last year Catania showed that eels can leap from the water to deliver their strike to a would-be predator. In that experiment, he relied on a fake human hand to endure the electrical attacks. But Catania wanted to measure the actual power of an eel’s zap, and a prosthetic wouldn’t do.