Rectus abdominis
Musculus rectus abdominis
// Structure & location
The rectus abdominis is a pair of long, flat muscles running on either side of the midline from the pubic bone to the lower rib cage. In the middle they are separated by a pale strip of connective tissue, the linea alba. Transverse tendinous bands divide each muscle into several segments, hence the six-pack pattern. Laterally it is wrapped by the sheet-like tendons of the oblique muscles.
// Function
It flexes the spine forward, the curling motion when sitting up from lying down, and tilts the pelvis backwards. Together with the other abdominal muscles it raises the pressure inside the abdomen, for example when coughing, straining or lifting heavy.
// For training & sport
- Crunches and leg raises train the flexing function.
- Ab wheel and planks challenge it to resist arching the back (anti-extension).
- In squats and deadlifts it works as a stabiliser, but doesn't fully replace direct ab work.
// Good to know
Whether a six-pack is visible depends mainly on the fat layer on top, not on muscle size. How many segments you have is fixed by the number of tendinous bands and can't be trained.