What is the primary function of the rectus abdominus during flexion?

The primary function of the rectus abdominus during flexion is to perform forward bending movements. This muscle, which runs vertically along the front of the abdomen, is primarily responsible for flexing the lumbar spine. When the rectus abdominus contracts, it pulls the ribcage closer to the pelvis, thereby facilitating movements such as bending forward or performing sit-ups. This action is crucial during activities that require the torso to fold at the hips, enabling efficient movement and functional performance.

While stabilizing the spine is an important function of various core muscles, the rectus abdominus is specifically engaged in flexion actions, making it a key player in forward bending movements.