So, after some of my church league softball games, a few of us hang around and try to strike each other out. It's a lot of fun but we had better be wearing our helmets when we step in. I get on the mound with my awesome 4 pitch repertoire: 4-seam FB, 2-seam FB, curve and changeup. All got markedly better (well, 65mph FB became a 68mph FB) after reading JimR’s tutorial and I started each by reaching way back at the start of my delivery. Except, something funny happens with the curve. If I short-arm the curve, it maintains a decent downward bite. If I “long-arm” the curve, it flattens out to a more sweeping break from like 2-to-7 and, more importantly, pops something in my upper back. Three times in the last 3 months and it hurts to move my neck for a couple of days. Right side (I’m right handed) between my spine and edge of the shoulder blade. What am I doing wrong?