Great question. I was thinking the same thing. If you live in the city, where would you get one? The junkyard, maybe? And how would you get it home or where you train? My apartment's too small I think.

We used to do a modified version of this on the mat flipping the heaviest bag we have end over end. I'm pretty much stuck on the tire thing too though.
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There are no PERFECT techniques, only perfect execution for the situation at hand. ~Corwin