As Joseph Pilates wrote in ‘Return to Life Through Contrology’, ” If your spine is inflexibly stiff at 30, you’re old; if it is completely flexible at 60, you are young”. He also specifically addresses the vertebra-by-vertebra movement of the spine and claims that this ‘rolling’ and ‘unrolling’ movement gradually restores the spine to its normal at-birth position with its corresponding increased flexibility.
Bridging is one of the basic exercises in Pilates. It is a great exercise to develop articulation in your spine. One benefit of this segmental movement is to eliminate muscle guarding, which leads to lower back pain. When learning how to articulate the spine, the global stabilizers are inhibited and the local stabilizers are firing, abdominals and the TA have a very big role in facilitating efficient spinal articulation.
Starting with the ‘Pelvic Curl’, which not only mobilizes the spine and prepares it for exercise, but also helps recruit the local stabilizers bringing focus to the ‘powerhouse’.
Progressing to the ‘Bridge’ and then the ‘Shoulder Bridge’, articulating the spine from tailbone through the tips of your shoulder blades, increases the strength of the hamstrings and gluteus. Furthermore, once in that bridge position the abdominals and hamstrings work together to stabilize the torso and the pelvic- lumbar region. Take a look at Amy and Rick’s book ‘Pilates and Conditioning for Athletes’ on pages106-109, and practice the exercises. Your back will thank you!
My favorite ‘Bridge’ is on the Pilates Reformer. Once you have mastered the mat work versions, here the challenge is the moving carriage. It is an excellent way to find that articulation of the pelvis and spine in flexion against gravity and with the assistance of gravity. The range of motion is greater because the feet are on the Foot bar of the Reformer, and the hamstrings have to work even harder in order to lift and lower the body. A further progression would be to add the extension of the hips and knees which requires more pelvic-lumbar stabilization.

Single-Leg Bridge
I hope you have a little more understanding of the benefits spinal articulation offers and will have more body awareness of what is happening when executing not only the ‘Bridge’ but the other spinal articulation exercises (to name a few) like ‘Semicircles’ and ‘Short/long spine’ as well.
Farida~