Readers know that we believe that jumping is an excellent and intense cardio-calisthenic for general athleticism. All I can do is singles and running jumps, doubt I will ever be able to do double-unders.
Anyway, my tech-oriented trainer introduced me to this cool thing last week: A rope which miraculously displays the count in the air in front of you with LED, and also sends the count to your smart phone.
Cool exercise toy. It's a heavy rope (as contrasted with light and medium-weight ropes), so it is extremely fatiguing for me. But that's the point - brief with high intensity.