Keep in mind this exercise can be modified by completing the push-up on the knees.
The most important function of this move is strengthening deep muscles of the abdominals and spine that make-up the "core." Focusing on pulling the belly button in toward the spine, while maintaining even breathing, and keeping the spine in-line is essential to protect yourself from creating pain issues or re-experiencing old pain issues.
Anyone with (unmonitored) high blood pressure, shoulder, or joint pain should check with their doctor prior to giving this exercise a go!