I dont think its worth the risk at all... If your weight shifts under you, you could blow your elbow or tear a pec or tricep.
I think the point is that chest presses on a ball aren't for heavy weights. Its an exercise to be done to improve stabiliser muscle strength using instability as a tool. If done properly, there is minimal or no risk.
Instability exercises are pretty popular at the moment. I was prescribed wobble cushion and balance ball weighted squats and lunges when I was recovering from my ACL. My physio wouldn't let me do them unsupervised until she was confident I understood how to do them properly though.
I think the point is that chest presses on a ball aren't for heavy weights. Its an exercise to be done to improve stabiliser muscle strength using instability as a tool. If done properly, there is minimal or no risk.
Instability exercises are pretty popular at the moment. I was prescribed wobble cushion and balance ball weighted squats and lunges when I was recovering from my ACL. My physio wouldn't let me do them unsupervised until she was confident I understood how to do them properly though.