Your waist is not a joint.
Bending is a whole body process that generally involves three sets of joints: the ankles, knees and hips. The waist isn\’t one of them. The hip joints are much lower than most people think, about four five inches below the waist. There is a video of this at Tip 58.
More information on your hip joints:
Three Tips on Bending Video & Article
Finding Your Hip Joints Blog Post
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