Abdominal muscles are an important part of human connective tissue, including rectus abdominis, oblique abdominis, oblique abdominis and transverse abdominis. When they contract, they can bend and rotate the trunk to prevent the pelvis from leaning forward. Abdominal muscles also play an important role in the activity and stability of lumbar spine, and can also control the activity of pelvis and spine. Abdominal muscle weakness may lead to pelvic forward tilt and increase the physiological curvature of lumbar spine, increasing the chance of low back pain.