The fastest man in the pool isn't Michael Phelps. It's Brazil's Cesar Cielo, who is psyching himself up to claim another gold in the 50-metre freestyle swim on Thursday.
It's how he psyches himself up that might make you cringe.
The 25-year-old world record holder thumps his chest so hard you can see the imprint of his hands. He says it motivates him and wakes up his body.
His record in the event, set in Rome in 2009 and in Shanghai last year at the World Championships, is 20.91 seconds.