Look at the diameter though.
How fast you have to go before your legs get blown backwards and ripped off? I hope there's some velcro.
I also wonder if he has considered a good dose of Preparation H before the run, to prevent inflating and exploding at top speed.. thhhhllllllLLLLLLLLLLPPPPPPPPPPPPPPPT BOOM!

Maybe a streamlined plug would be smart.