What muscles are used in a bowling back swing and how do you exercise them?

[Derek Tran]

I am male, 5'6 and don't have that much muscle on me (slightly overweight at 150lbs). I bowl with a hook and used to use a 12 lb ball (three fingers, finger tip). My form was bad because I had a small back swing and muscled the ball down the lane with a string hook. My elbow was bent throughout the approach and delivery to crank the ball. I recently decided to get a new ball the the pro shop told me I can handle a 14 or 15 and that it would be better. I got a 15 lb virtual gravity. I'm trying to fix my form now and get a good push away, lock my elbows, get a good back swing, and still be able to crank the ball a bit. I mostly need more speed to get it down the lane before the VG breaks (it breaks really early) which tells me I need a bigger back swing. Unfortunately, I can't keep my arm straight and get a high back swing cause the thing is too heavy. My elbow bends/unlocks, my wrist form breaks, and the ball barely goes up. My arm just gives out. In the end my arm is so out of whack, I completely miss my mark and more times than not, the ball hooks mid-lane (not enough speed), or it doesn't hook at all.

So my question is, what are the major muscles involved in this action and how do I exercise them?

I assume my posterior deltoid and anconeus need the most work, as well as my forearm for grip and wrist form, but I have no idea how to exercise these effectively.

Thanks for your help!