The rubber band can only bend so far before it swings back.

橡胶棒只能弯曲这么多，接下来就会反弹。

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Keep back straight and bend knees.

背要直，只弯两膝。

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If you can bend back your thumb to touch your lower arm, the ligaments in your feet are probably stretchy, too, Dr. Gastwirth said.

Gast wirth博士说，如果你能扳回拇指弯曲并触摸到下臂，那么你脚下的韧带也可能很有弹性。

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He asks me to help him into a back-bend by using my ankles for support.

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Then, at the same place, bend it back to form a right-angle in the opposite direction.

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