Is it okay for a ten year old's back to hurt?

Inclined sit-ups. Stretching is easy to learn. But there is a right way and a wrong way to stretch. The right way is a relaxed, sustained stretch with your attention focused on the muscles being stretched. The stretches should be slow and easy, not unlike a long yawn and stretch done upon awakening. The wrong way (unfortunately practiced by many people), is to bounce up and down, or to stretch to the point of pain. These methods can actually do more harm than good. And good luck.

I don't understand what you mean about stretching, but she could have some kidney problems, that is the cause of some back pain.

If she stretches normally, she might have pulled a muscle, it happens to me all the time. Try massaging it.

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