Thanks for writing to us.
The tightening of the abdominal muscles every now and then may be related to the pinched nerves at the level of spinal cord
due to the protruded discs. You need to get yourself examined by a neurologist
to know the exact cause. Taking muscle relaxants may be helpful.
I hope this information has been both informative and helpful for you. You can consult me again directly through my profile URL http://bit.ly/Dr-Praveen-Tayal
Dr. Praveen Tayal