Herm Sprenger Rubber Ball

This ball is as hard as a rock. It is also very heavy. I have always had good luck with Herm Sprenger prong collars, so I assumed this ball on a rope would be something I could incorporate in my puppy's training program. If I tried to swing this around as a reward, it may hit my leg and be painful or break my kneecap. My puppy is over 100 pounds at 9 months old, but I am afraid I will hurt myself with it. I cut the rope off and will use it as a fetch toy. It seems very well made, but not suitable as a training reward.