Popping exercise ball

So vague now, I remembered more earlier but it faded quick. I was in a massive sports complex, looked like a big indoor swimming pool with mega high ceilings. There was a woman there, my age, who I think was teaching some kind of fitness lesson. She looked like Steph C from high school. I think I was either learning or just watching what she was doing. She had a giant yellow exercise ball, as tall as her, and I don’t remember what exactly she was doing with it but she was demonstrating something. It popped right in her face and she fell backwards, stunned. I jogged over to her and she was fine but dazed and complaining that she’d be deaf for a few minutes. It was loud. And I remember immediately glancing at the other balls and wondering when their time would come. I figured they’ll all pop eventually and it was just this one’s time.