What happens to stomach muscles if the pelvis doesn't move properly?

The abdominals' role in stabilizing the spine is somewhat dependent upon pelvic orientation. If the pelvis isn't moving well, then the abdominals will not be able to stabilize the spine well. This permits poor movement habits to develop, which then reinforces the original pelvic and abdominal issues because they are not challenged adequately to be restored to their proper length and tension. It is similar to issues seen in the elderly who sit for long periods of time. Their leg muscles then become weaker and hip range of motion decreases, making it more difficult to stand and walk, which then compels them to sit for longer periods of time. Prolonged sitting encourages muscles weakness, and the cycle continues.