Excerpt from Bowling Fundamentals - Second Edition By Michelle Mullen
Bowling balls range from 6 to 16 pounds in weight. For youths, a general rule of thumb is to use a ball that is about 10 percent of their body weight, give or take a pound of two. That can be a bit vague. When instructors help bowlers decide what weight to use, they watch them bowl, with a house ball if necessary, to determine when their swings look best.
If you are trying to choose a house ball, you have to consider that they are predrilled, not custom fit to your hand. Therefore, you may not find a ball that is the desired weight. When instructors watch bowlers use a house ball to determine the proper weight for a new ball purchase, they have to take into consideration that the new ball will fit so much better and, therefore, that the bowler may be able to go a pound heavier than the house ball. Balls that fit well feel lighter.
If your ball is too light, you will be able to overpower it and it will be hard to have a consistent swing that also stays in alignment. You need a bit of an anchor at the end of your arm to develop the pendulum effect in the swing. However, you do not want a ball that is too heavy. Bowling well does not require choosing the heaviest weight. It takes strength to let a heavy ball swing through a full arc. If you labor at all to let the ball easily swing through a full arc, or if you struggle to do this easily over the course of the number of games you typically bowl, then a lighter ball would be better. Go only as heavy as you can while still being able to stay in form for the duration of the time that you bowl.
I liken this concept to that of being at the gym and wanting to lift heavy weights but not able to do so with proper form or to complete any substantial number of reps with them. It takes strength training to develop the ability to stay in form with more weight.
More weight is not necessarily better! At one time, the cores of bowling balls were a lot weaker, and the hitting power of the balls did depend more on ball weight. Nowadays, cores have gotten so strong that in some cases they account for approximately half the weight of the ball! Bowling balls today hit harder, even in lighter weights. For this reason, many of the male professional bowlers do not throw 16 pounds. If you have to labor to push the ball into the swing or cannot let the ball swing fully into the backswing, or if your ball speed is too slow, consider using a lighter ball.
Just because you throw the ball hard does not necessarily mean that you need a heavier ball. Consider that the top professional bowlers have good speed and strong ball roll. Sometimes, the illusion of throwing it too hard is really a matter of having ball roll that is too weak for your speed. If this is the case because your wrist is in a weak position, more ball weight is not the answer. Rather, a firmer and stronger wrist position is necessary to create a stronger ball roll. This would be harder to achieve with a heavier ball.
In some cases, a wrist guard is warranted to strengthen the wrist position and create stronger roll. Candidates for wrist guards are those with weaker wrists or who firm up the wrist by creating more grip pressure or tightening the muscles during the swing. This is very common. Different muscles are used to strengthen the wrist position than are used to hold or swing the ball. Wrist strength aside, bowlers need to firm up wrist position without increasing grip pressure or tightening the swing. Those who can't should consider a wrist guard.
Mullen, Michelle. Bowling Fundamentals- Second Edition.
Champaign, IL: Human Kinetics, 2014.