This has had me puzzled for a while..
I love cracking my thumbs, and I can do it almost continuously. When I first started, I only had one method for effectively getting the topmost joint of the thumb to crack, which was to fully bend the thumb. Then I started cracking it by simply bending the topmost joint of the thumb and leaving the rest of it straight. A few weeks ago I developed a third method: same as the second, but bracing the tip of the thumb against a hard surface (my jawbone works well) and pushing against it as I bend the joint.
So, with three ways to get my kicks, all was well and good. If one method failed, then I could just try another, and then a third if necessary. Here is where my confusion comes in, however. I can crack my thumb, using all three methods, three times in quick succession. It feels like I am cracking the same joint, but how is this possible? I know, at least for me, each joint has a sort of "refractory period" where it can't be cracked again, no matter what I do, for a certain length of time. I can crack the thumbs a lot each day, but not constantly. I'm just wondering how I can do this to get three successive pops in the same joint just by flexing in different ways? And does anyone else experience this?
Each method also produces a rather different feel to the cracks as well. First method makes a deep, satisfying crack or snap, but can't be done as often. The second method produces a sharp sound, and is harder to achieve than the first, while the last method is low, soft, and the least satisfying of the three, but it can be achieved very easily.
This also made me wonder if the mobility or usage of a certain joint affects the rate at which you can pop it. My fingers, toes, and back crack most often, which makes sense considering how much those joints move and work during the day, especially the fingers.