It's a bit difficult at this age, because it's a bit tight not to pull all the time, but as long as you are willing to work hard and stick to it, you can definitely pull it open.
3' is the simplest and most practical, and other methods are not very practical and convenient.
Four-foot bounce? Ever heard of sandbags tied to your feet? A pair, 5 kg per pair, can be conveniently tied to the feet and carried when walking and jumping every day. The price is about 100 yuan.
Ps: We must persist in everything.