You *might* find after doing lots of repeats, that you have some particular weakness like in the arms or shoulders or something and *maybe* some off the bike supplemental exercise *might* help but really it's what's been said...specificity. My take, FWIW, is that's particularly true here. Think about what is entailed. Other than actually doing it on the bike the nearest thing I can think of would be running up stairs on a ship in heavy seas. Maybe lobstermen are great climbers.