I was doing rear delt flies yesterday and all hell broke loose. One isolated abdominal muscle was super tense, poking out about .5", with the rest at rest. The pain was fairly agonizing. It was initially sore, and still doesn't feel right, but its not painful. Any ideas on what it is? I should probably stay out of the gym for a few days right...even though that would make me a pussy who lacks stongminded?