The first action is to twist sit-ups. Students are not required to do sit-ups in junior high schools now. It is said that the harm of sit-ups is waist injury, which is a permanent injury to many untrained girls. Of course, some people can do it well. However, for students, this kind of torsional sit-ups may lead to local muscle traction injury due to the large torsion range, so the possibility of injury will be higher.
The second is to bend over and pull hard. This action can also lead to muscle injury. After all, the purpose of exercise is to improve physical fitness and make yourself healthier. However, doing this action may cause damage to the lumbar spine. This is hard to recover. After all, time waits for no one. Your purpose was to keep fit, and you got hurt. It's really not worth the candle, is it?
The third action is to bend down. This action needs a long time of exercise, not at the beginning. If you come directly from the beginning, you will strain your lumbar muscles and may even cause obvious damage to your lumbar spine. Be careful. If you have a waist injury, then your happy life may be far away from you. Do you think it is necessary to exercise like this? I don't think these moves should be tried!
If you want to stay healthy, you need to take your time. Of course, you can do it under the guidance of a coach. If you feel a little tired, take your time. It can't be urgent, can it?