The only evidence you need for this one working is a glimpse at a beach volleyball pro. They are some of the fittest humans on earth. “In beach volleyball, you’re sprinting, diving, jumping, and dodging, all of which increase your heart rate and adrenaline, like interval training,” says Rappoport. And since sand is an unstable surface, you’ll have to use your stabilizing muscles to stay upright. You’ll also need more force to push off the ground when you spike. The result is a full-body workout that will leave you sore for days. A half-hour game burns about 330 calories.