There is a region in the Philippines where they eat corn instead of rice as a staple. In fact, many of the successful boxers come from that region and they attribute their strength to corn. I don't know if there are riders shifting to corn for the touted strength and stamina but I have read of some upcoming boxers eating corn during the training period. If corn is really effective for stamina, I think that would be a great plus cyclists particularly those joining national competition.
Aside from cooking corn like how they cook rice, corn is also good to be eaten when boiled. But broiled corn is not that effective. So that means popcorn is not that effective either.
Aside from cooking corn like how they cook rice, corn is also good to be eaten when boiled. But broiled corn is not that effective. So that means popcorn is not that effective either.