Ride 20 miles in under an hour on flat ground.
I can't........at least not now and maybe never. Last summer I managed to sustain about 18mph for a few miles but that was significantly down wind with a rabbit in front of me to chase. 20 minutes of that and I was ready to die.
I was reading about a race coming up near here and the 50+ crowd is targeted for 40 laps on a 1/2 mile stock car track. Time alloted for the race 1hr. How many here could even contemplate such a thing.