Q: How long can a grizzly run at full speed? How much of a head start would a person need to outlast a bear chasing them? —Tarahumara Man, via email
A: Sigh. It seems like there's always some human who wants to figure out a secret way to best me on foot. Can't you just be happy that you're (sometimes) smarter than me and have access to modern plumbing? It'll have to do, because there's pretty much no chance you'll ever be faster than me.
It's well-known that I can reach speeds of up to 35 mph; some scientists think I can even go faster than that. What's less known is that I also have incredible endurance: On multiple occasions, scientists in Yellowstone have clocked grizzlies running 25-28 mph over a distance of two miles, and according to observers, I wasn't even breaking a sweat. I was moving at a "rolling lope." Another report clocks me running at 30 mph over a quarter mile, and notes that these are speeds clocked on asphalt (I might gain even faster speeds on dirt where I can use my claws).
The fastest clocked human speed is in the neighborhood of 27 mph, and this slow human (Donovan Bailey) couldn't maintain it for much more than a few milliseconds of his sprint. Even the more consistent Usain Bolt tops out at a pokey 23 mph over 100 yards, lasting a paltry 9ish seconds.
So even Usain Bolt and Donovan Bailey (two of the fastest humans ever) can't compete with me. You'd need a head start of over two miles, at which point you couldn't even detect me (but I might detect you). If you're in my zone of awareness and decide to challenge me to a foot race, you can't win.
So stick with what you're good at: Forget your feet and use your head instead.