Sometimes when I see my chiropractor, she manipulates my back with me lying down and sometimes sitting up. Why is that?
There are different types of manipulation procedures that can be done on the spine. Some techniques can be done in more than one position. The location of the problem and the patient's individual anatomic variations may direct some of the chiropractor's decision about the techniques (and positions) used.
For some patients, it may be possible to get better leverage by using a supine (on your back) position. The force of the patient's body along with the downward thrust of the manipulation may be needed to make the necessary correction of spinal alignment.
Sometimes the chiropractor's size (compared with the patient's size) figures in on the equation. The more specific the manipulative treatment can be, the better the results. These are just some general thoughts on your experience. You will have to ask in order to know for sure why your chiropractor uses different positions and techniques.