What muscles help with lumbar flexion?

Answered by Douglas Hiatt

The muscles that play a significant role in lumbar flexion are the Rectus Abdominis, internal oblique, and external obliques. These muscles work together to flex the lumbar spine, which involves bending the lower back forward.

The Rectus Abdominis is a pair of long, flat muscles that run vertically along the front of the abdomen. It is commonly referred to as the “six-pack” muscle due to its appearance in well-developed individuals. The Rectus Abdominis originates from the pubic bone and inserts into the lower ribs and sternum. When contracted, it pulls the ribcage closer to the pelvis, leading to flexion of the lumbar spine.

The internal oblique muscles are located on the sides of the abdomen, deep to the external obliques. They have a similar fiber orientation to the external obliques but run in the opposite direction. The internal obliques originate from the iliac crest and insert into the lower ribs and linea alba, a connective tissue structure in the midline of the abdomen. Contraction of the internal obliques on one side causes ipsilateral lumbar flexion, while contraction on both sides leads to bilateral lumbar flexion.

The external oblique muscles are the outermost layer of the abdominal muscles. They have a diagonal fiber orientation that runs from the lower ribs towards the midline. The external obliques originate from the lower ribs and insert into the iliac crest and linea alba. When contracted, they assist in lumbar flexion by pulling the ribcage closer to the pelvis.

The nerves that innervate the Rectus Abdominis are the Intercostals (7-11) and Subcostal (T12). These nerves arise from the thoracic region of the spinal cord and provide motor innervation to the abdominal muscles. They also provide sensory information from the skin overlying these muscles.

In my personal experience, strengthening these muscles through exercises such as sit-ups, crunches, and leg raises has been beneficial for improving lumbar flexion. However, it is important to note that lumbar flexion should be performed with caution, especially for individuals with pre-existing back conditions or injuries. Consulting with a healthcare professional or a qualified fitness instructor is advisable to ensure proper technique and prevent any potential harm.

To summarize, the primary muscles involved in lumbar flexion are the Rectus Abdominis, internal oblique, and external obliques. These muscles work together to bend the lower back forward, and their contraction is innervated by the Intercostals (7-11) and Subcostal (T12) nerves. Strengthening these muscles can be beneficial, but it is important to exercise caution and seek professional guidance if needed.