When you can't walk the foot any farther forward without lifting it off the floor, straighten the knee as much as you can, powerfully reaching the foot forward and out to the left side.

当左脚无法前移时，就尽量伸直左膝，向左前方有力地伸展。

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Stand in a doorway, hold the door frame on each side and walk forward until you feel a stretch in your chest.

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