Video: Floyd Mayweather Jr holds stack of cash while training in gym

Pound-for-pound boxing king Floyd Mayweather Jr decided to hold a stack of cash while training this week ahead of his fight against Andre Berto.

The 38-year-old American, who will face Berto in September, regularly boasts about his wealth on social media.

This time, a video posted on the mayweatherunlimited Instagram page shows the sportsman grabbing a wad of money and using it as "motivation" while firing punches with his left hand.

Mayweather is unbeaten in 48 fights and has vowed to hang up his gloves after his 49th win.

A video posted by @mayweatherunlimited on Aug 25, 2015 at 10:52am PDT