Mastering the double-under in my opinion is all about staying relaxed, focused and letting your wrists do the work. Before you start jumping take a good breath in from your belly (not your chest) and then exhale. Next pick a focal point on the wall and keep your eyes forward. Doing this will help set up good midline stability. Last, concentrate on keeping your elbows in and let your wrists make each revolution on the rope. The farther your arms are from your body the shorter and less tension you have on the rope. This makes it very difficult to maintain good speed. Try these few tips and see if you link together a personal best in your double-under! – Coach Bryan