Hi sakerwalla,

Your last post did it for me...it sounds like a thorax dysfunction causing myofascial referred pain.

The 'pop' doesn't sound that serious.

She was nearly finished in the race - she only had 5 more miles to go so was 80% through the race - fatigue is likely and she probably went into a habitual motor pattern and likely overused her obliques to help her breathing or stability (i don't think her core stability is that good if the belt helps her BTW )

The thorax experts are definitely LJ and Diane Lee, LJ esp in the rehab side of things.

Good luck with her - the Wikipedia reference-linkSIJ is likely to be secondary to the thorax giving way.

BTW, thanks for the good posts sharileedahl!