^But bad for the knees...I definitely don't recommend using them while jumproping, I felt the instant pain in my knees and I never had knee problems. Just do step-ups, like use only one leg and step up on a chair but don't use the other leg, come down and repeat alternating legs. Great on quads. And do lunges with dumbbells in your hands, great on hamstrings. For calves, use them doing ankle lifts on stairs.