1 Treadmill: At present, there is basically no treadmill driven by human power, so don't stand on the running belt to drive the treadmill. Just turn on the power and set the speed. It should also be noted that when the treadmill starts, don't stand on the running belt first, but stand on both sides of the running belt and wait for the running belt to run for a while before running on the treadmill.
2 chest expander and other fitness equipment: nothing to pay attention to. Anyway, you should master the strength yourself, don't use too much force, and take it slowly to prevent the heavy objects on the equipment from suddenly falling down and breaking the equipment.
Dumbbell: Do what you can, not recommended by teenagers. This will have an impact on growth. Don't be too fierce, or you will fall and hit your foot.