The big ball that you mentioned looks like a toy. It can be called a fitness ball. This rubber fitness ball can withstand up to 400 kilograms of pressure. Fitness ball is a novel, interesting and special sport. Nowadays, fitness ball is especially favored by urban women because of its interesting, soothing, safe and obvious effect. Fitness balls can exercise the muscles of the chest, abdomen, back, buttocks and legs, which play an important role in maintaining body balance, improving body posture and preventing sports injuries.