Swimming sensation Michael Phelps spent countless hours in the pool training to become the most decorated Olympian in history.
He also spent countless hours in bed, sleeping.
Phelps says training and sleeping were equally critical when it came to acquiring his stack of 28 Olympic medals.
"At a very young age I learned how important sleep was," says Phelps, who spoke to CNBC about his training habits from the New York City showroom of direct-to-consumer mattress brand Leesa. The Olympian has recently entered into a four-year brand partnership with the company.