Rob Sulaver, CPT, CSCS, founding trainer at Rumble Boxing in New York City, said to keep in mind the strength it requires to do a one-arm push-up. "We use about two-thirds of our body weight when doing a push-up from our toes," he told POPSUGAR. "So, the real trick to being able to do a one-arm pushup is to be able to single arm press at least 66 percent of your bodyweight."
After you're able to press that much weight, your journey towards being able to do one-arm push-up is that much easier. Sulaver recommends building your upper body strength with bench pressing on an incline and a decline, and flat pressing with a barbell, dumbbells, or a machine. Using cable flies and dumbbell flies will also help, as well as doing push-up variations. "It takes a bit of practice to get the balance right, but with enough strength and a proper set up, a one-arm pushup isn't nearly as intimidating," he said.