Occasional pain under right ribs when i sit up too fast or sit down with force only lasts 30 seconds. how to tell if muscle spasm or something else.

Muscle spasms: When you sit up rapidly & have pain immediately is probably from a spasm in the diaphragm radiating from your right side of your back. It may also be from your gallbladder having some sludge or stones present but I think that is doubtful. If it gets worse or persists beyond 3 or 4 days.Go see your Dr or go to the E/R for evaluation.

If muscle: then it is likely reproducible by twisting, touching, moving and breathing. If severe pain and persistent , constant and unable to take shallow breaths you'll need to be evaluated at an urgent care or emergency room. Good luck