When it comes to mixing up his exercise routine, celebrity trainer Reggie Chambers, who's worked with stars such as Christina Ricci, and Alison Williams of HBO's Girls, loves the jump rope. "It's one of the most effective cardio 'machines' one can use," he told me in an interview. "First of all, it could be done almost anywhere because it's small and portable!"

Turns out jumping rope is also super effective. In fact, Chambers explains that just 20 minutes of jump rope is equivalent to about 45 minutes of less intense cardio. Plus, it can be pretty fun. "Once you become good it, you can do a variety of jumps to make it more effective and not boring," Chambers said.

Mohamed Elzomor, head trainer at NYC's Core Club, is also a big fan of the jump rope. "This is a quick way to burn calories and challenge your endurance, and your hand-eye coordination at the same time," he told me.