What is the primary action of the rectus abdominis muscle?

The primary action of the rectus abdominis muscle is spinal flexion. This muscle runs vertically along the front of the abdomen and is primarily responsible for bending the torso forward. When the rectus abdominis contracts, it pulls the ribcage and the pelvis closer together, resulting in the spinal flexion movement, which is essential in many activities such as sit-ups, crunches, and even movements like bending forward to pick something up.

The rectus abdominis is vital for core stability and plays a key role in maintaining proper posture. It also assists in various functional movements, including forward bending motions and stabilizing the pelvis and spine during dynamic movements. Understanding this muscle's primary action helps in developing effective core strengthening and rehabilitation programs.