Always hold your hands by your ears rather than behind your head so you don't strain your neck or back.

记住一定要把你的双手放在你的耳朵边上，而不是在你的头后，这样就不会拉伤您的脖子或者后背。

youdao

The hot-spot adjustments: Either lean back, resting your hands on the bed behind you, or lean forward with your hands above his head.

热点调整：不管是向后靠，把双手放在身后的床上，或者是前倾把手放在他头上。

youdao

Can you bend your thumb backwards until it touches your wrist? If you join your hands behind your back, can you lift them over your head without letting go?

你是否能将大拇指向后弯曲直至其触碰到手腕部位？你将双手在背后紧握，是否能够将其举过头顶而不松手？

youdao