When people learn that I run 100-mile races, they sometimes say, “Whoa, extreme.”

It’s not that extreme, really. Yes, I lose toenails from time to time, and I once lost my ability to taste food (pizza, chocolate cake, even Coke all tasted as bland as sand). But that’s the weirdest side-effect I’ve experienced.

It’s not like I race down the side of a mountain on a bike:

This eye-popping urban bike race takes place on the ancient streets of Valparaiso, Chile. Riders have to deal with brain-melting jumps, flights of stairs, and even, as you’ll notice at the 37 second mark, stray dogs.

I’ve been watching tons of these videos lately, since I’m writing a novel about a kid who spends all his spare time mountain biking.

But recently I’ve been thinking about changing the plot of the book – thanks to this video I saw about wingsuit jumping. Did you know that there are people who jump off mountainsides wearing plastic wing-suits? They look a bit like flying squirrels. Except they fly at 125 mph.

For every foot they travel down, they also travel one foot out. A typical flight lasts 10 seconds, and ends with a parachute being deployed.

Now that’s extreme.