Bowling requires the upper and lower body to work independently from each other. The finish position exemplifies this with your shoulders going in one direction and your hips going in another.
A good exercise to train your lower body to work independently from your upper body is the lower body roll. This exercise is done with your back on the floor utilizing your lower body to move your entire body by rolling with just your legs. Keep your upper body as still as possible; making it heavy for your lower body to move.
Lie on the floor with your arms extended over your head.
Next, you’ll roll from the backside of your body to the front side of your body using just your legs. Start your roll by lifting your leg into the air and drop it across your body. As your leg drops to the floor, the rotation momentum will bring the upper body along with. Repeat the process as you lie face down using the same leg to get you back to your starting position.
When you’ve completed the exercise with your first leg, move on to the second leg doing the same amount of reps to avoid imbalances. This exercise makes it easier for the upper body and lower body to do two different things at once. Add it into your workout routine and you’ll feel the difference at the foul line the next time you bowl.