NEW YORK (Reuters) - Paddle boarding, an ancient form of surfing, is gaining popularity as a high-intensity, low-impact platform for group fitness classes from calisthenics to yoga. Experts say it may feel like walking on water because paddle boarding works on the flat water of a lake or pond and doesn't involve waves. "Paddle boarding is a form of surfing. A paddle board is basically a surfboard that's thicker, more buoyant, so it can hold you standing up in flat water," said Scott Bumbalough, founder of Maui B's Stand Up Paddle Boarding, which is based in Florida. ... read more..