Sweat It Forward is a rolling challenge, between New York City's top fitness studios, which kicked off in March 2015.

In April 2015, the challenge went NATIONAL, and readers can now challenge their friends and colleagues — either to complete a physical challenge, or donate $35 to Stand Up to Cancer. Either way, they Sweat It Forward to the next person! Are you up for the challenge? See the rules and details below...

Sweat It Forward is sponsored by ReebokEssentia Water, and benefiting Stand Up To Cancer.