Pain on bending on waist is likely due to muscular pain. Pain on movements are due to sprained muscles (strained abdominal and waist muscles). Treatment is as follows;
1) passive stretching of the affected muscle after application of sprayed vapocoolant.
2) physical therapy; simple muscle stretch, augmented muscle stretch, post-isometric relaxation.
3) deep electrotherapy; iontophoresis, phonophoresis, short wave diathermy, electrical stimulation, high voltage galvanic stimulation, biofeedback.
4) local analgesic patch / ointment / spray
5) anti-inflammatory analgesics; Ibuprofen (Motrin / Advil)
6) ischemic compression therapy; pressure on the points
8) steroid shots
Please feel free for your follow up questions.