So, there’s many different ways you can do crunches on a bosu ball, in fact I think one of the purposes of a bosu ball when it first started was for crunches just like you could do them on a regular stability ball. So what you wanna do when you’re doing a crunch, is you wanna make sure that the small part of your back, the lower back right here fits right in, so it’s kinda like a nook so make sure that your, there’s no space at any point between the ball and your back so it’s all covered for. Then you wanna put your hands behind your head and you wanna just lift up and lower. So, now there’s different ways to do this, so if you stay close to where I am, you’re kind of higher up on the ball so you’re lifting and it’s just a small little lift right here and you’re working more just the middle and upper abs. Now if you push yourself back a little bit and hang off of it a little bit more, then you wanna go back all the way and you just come up to about flat and you’re gonna feel it a lot more in your entire a so the lower and everything, so everything kicks in you’ll probably start shaking. Now some people have lower back issues when they’re using a bosu ball that’s why it’s really key to make sure there’s no space in between your back and the bosu ball and you’re pressing down on your stomach, which presses down on your back, which presses down in the ball and that’s how you lift. If you’re not pressing down and you’re just lifting with your neck or whatever your back is probably gonna start to hurt and just keep in mind as well you wanna make sure if your back does start to hurt you’re not ready for this that you maybe move on to something else, like floor crunches before you come on to this, because it is a little bit more straineous. For more advanced people you might wanna take a dumbbell and you can bring it behind your head and then you just lift the same way. Again you’re pushing your stomach into your back, your back into the ball and that’s why you lift, not because you’re pulling on your neck.