Question
Sometimes when I am sitting down for periods of time and I arch my back, my chest cracks.  Do you know how this is caused and what I can do to reduce or alleviate this?

Thanks.  

Answer
Stan,

Thanks for the question.  This is usually caused by movement or calcium deposits in the costal cartilage (where the ribs meet the cartilage surrounding the sternum).  In some people, when performing the movement that you describe, calcium deposition in the cartilage itself can make a cracking or popping sound.  This is not harmful or dangerous, but it can cause decreased ribcage expansion.

I hope this helps.

Dr. Boss