Mid back pain after jumping is related to the curvature of the spine and the back and the body’s center of gravity at landing and on impact.
When the body descends, the center of gravity of the body must be centered, the body must be balanced, and the spinal cord and back should be straight. The upper body must not be tilted forwards or backwards.
If the back is curved or if the spinal cord is not straight at time of landing and on impact, the landing impact will be a concussive impact that will compress the spinal discs. This compression of the spinal discs will misalign the discs and cause disc herniation. This herniation is the cause of pain in the mid back.
Again, do stretching exercises to alleviate the mid back pain. Check to see if there is any spinal disc herniation by running the hand over the spinal cord to see if there is any indentation or protrusion of the spinal cord.
There are exceptions to this. If one watches Olympic gymnastics, one will often see the gymnasts dismount from the uneven parallel bars or from the “horse” and land on their feet with straight legs but with upper torso bent and arms spread like wings to the sides. The arm spread and the torso bend are for balance immediately following the landing impact. This landing posture comes from the fact that while in the air, the gymnast’s body is curled up in order to bring the legs and feet either forwards or backwards for a solid landing. The landing posture is the result of unfurling the body.