When Gregory Taylor and Mark Chavez weren’t practicing medicine, they worked on creating fitness balls they hope will make exercise convenient and fun.

The M.D.s developed a patented line of brightly colored weighted devices – one is roughly the size of a volleyball, the other a softball – that weigh between 2 and 11 pounds. The balls feature Velcro handles, extender straps and anchors to adapt to different exercises.

“It’s like the Swiss Army Knife of medicine balls,” said Taylor, medical director of Keck Medicine in downtown Los Angeles.

He and Chavez, a longtime friend who practices family medicine in Pasadena and created the devices in his Long Beach apartment, launched Gravity Ball Fitness in 2011 and enlisted fitness instructor Melissa Vogel to teach classes using the ball at Canyon Fitness Center in Lake Elsinore.

Gravity Ball Fitness plans to embark on a crowdfunding campaign next week to raise $25,000 to mass-produce and market the larger balls. The company wants to manufacture up to 500 with the money, selling them as a package with attachment loops and online videos and guides for about $125. They’ll initially target consumers directly before expanding to include local gyms and teaching a Gravity Ball Fitness instructor certification course.

“We raised about $100,000 in private investment, but that cost a lot of equity,” Taylor explained. “We’re at the stage where we want to do something small and not crowd the pool, to hold on to as much equity as possible and think about expansion.”

– Marni Usheroff