Minimum 2.7 meters, no upper limit. When the gym is renovated, floor-to-ceiling windows can be installed indoors to ensure sufficient air circulation and sufficient light source in the gym. When decorating the gym, you can put some potted plants or vines in the gym appropriately to make the space green. It's best to hang some full-length mirrors when the gym is renovated. It is not that people who like sports also pay attention to their physical changes and let people observe the effect of sports.