Basic crunch on a stability ball comes after you've mastered it on the floor so, now we've taken out center of gravity here. We've added in a cushion of air for you to maintain balance with. It's also going to support your low back, but don't forget to maintain neutral pelvic posture by holding a soft contraction, not to impair your breathing, but just enough to support your lumbar spine. So you're going to come back and you're going to put that ball right into the low back, right where your back tends to curve, support it there and, the further out you bring your feet, the easier it'll actually be. The closer they come in, the more you've got to control that momentum as you crunch. So, starting with your fists right underneath your chin and you're going to gaze as you crunch, exhale, through your knees, towards your abs, but not arched. And hold, and release to a point where you feel your hip flexors kind of relax. So you're going to have to control, you're going to have tight hamstrings, active gluts, feet in line with the hips, inhale and crunch and release. Now, just like if you were working with the floor for a surface, you don't want to come all the way back on your release because that's going to take you out of neutral cervical posture. So, inhale and crunch and release. And I guarantee, especially if it's your first time, on about that first ten you're going to feel all that tremor too with all that shaking going on, it's just the muscles asking for oxygen. So, take a moment to stretch, breathe, work your way up to the ten and then add on from there.