Back when I used to race mountain bikes I would find that on long, grinding, full effort climbs I would sing the "C is for Cookie" song from Sesame Street. I have no idea why, but it came into my head repeatedly and it somehow helped me keep my cadence and focus. I didn't think I actually sung it out loud, I thought it was more of mental thing. Then on one multi-lap race I passed a guy going up a brutal hill for the third time and I heard him singing the same song. When we got to the top and both caught our breath I said "Dude, that's weird, I sing that same song when climbing." He said "I know, I heard you on the last lap and now it's stuck in my head you #*@!"

Edit: I hadn't thought about this in years and now the song is stuck in my head again. Dang!