I ve recently gotten back into working out this past week. I went to zumba for an hour monday night and went pretty hard, and these past mornings i ve been getting up and working out (sit ups, push ups, crunches, and side leg lifts) for 20-45 minutes. I just only noticed this a few days ago: my left side of my rib cage is sore up top and seems to be sticking out farther than my right side. It doesn t hurt when i breathe deeply, but i m just nervous. Is this normal? Is this due to my morning workouts? Is this Costochondritis? Thank you for your help.