I ve been working out my back at the gym for two of the past four days, and today I went to a trampoline park to work gymnastics into my schedule - within the first 10 minutes, I started feeling pain in my mid-to-upper back every time I landed. The pain grew exponentially throughout the next hour or so, until it started severely disturbing my breathing, which became shallow and labored. Now, after the workout, even during a simple jogging motion, I feel pain in my back on every landed step, and the breathing is still in the same condition. A bruised rib seems off the table since no trauma preceded the start of the pain.