GENERAL INFORMATION
The abdomen is a region of the body located between the thorax (chest) as well as the pelvis. It contains various organs, including the stomach, liver, intestines, kidneys, as well as reproductive organs. Additionally, the abdomen is surrounded by several layers of muscles, including rectus abdominis.
RECTUS ABDOMINIS
The rectus abdominis is a long, paired muscle that extends vertically along the front of the abdominal wall. Commonly referred to as the “six-pack” muscle, it features visible tendinous intersections that create distinct segments.
ORIGIN
The rectus abdominis originates from the following structures:
- Pubic symphysis: A cartilaginous joint between the pubic bones
- Pubic crest: A ridge of bone located on the front side of the pubic bone
INSERTION POINT
The muscle inserts into the following structures:
- Xiphoid process: A small cartilaginous extension at the lower end of the sternum (breastbone)
- Costal cartilages: Connective tissues that attach the ribs to the sternum (except for the floating ribs)
MAJOR ARTERIES
The rectus abdominis receives its blood supply from branches of the following arteries:
- Superior epigastric artery
- Inferior epigastric artery
NEURAL INNERVATION
The muscle is innervated by the lower intercostal nerves (T7-T12) as well as the first lumbar nerve (L1).
TRIGGER POINT
The rectus abdominis can develop trigger points, which are localised areas of muscle tightness as well as tenderness. These trigger points may refer to pain in the abdominal region, lower back, as well as groin area.
CONCENTRIC FUNCTION
The concentric function of this muscle involves the contraction of the muscle fibres, resulting in flexion of the trunk. When both sides contract simultaneously, it contributes to trunk flexion or forward bending.
ECCENTRIC FUNCTION
The eccentric function of this refers to the controlled lengthening of the muscle fibres. This assists in trunk extension and controls the speed of trunk flexion during movements like sit-ups or lowering the torso back down.
ISOMETRIC FUNCTION
The isometric function of the rectus abdominis involves maintaining a static contraction without any change in muscle length. Thus, it helps stabilise the trunk and maintain posture.
RELATED MUSCLES (SCIENTIFIC NAMES)
- Transversus abdominis: The deepest abdominal muscle, essential for core stability and compressing the abdominal contents.
- Internal oblique: Assists in trunk rotation and lateral flexion, providing deeper support for the abdomen.
- External oblique: Located on the sides and front of the abdomen, crucial for trunk rotation and lateral flexion.
ANTAGONIST MUSCLES
- Erector spinae muscles (iliocostalis, longissimus, spinalis): Extend and rotate the spine, opposing the flexion action of the rectus abdominis.
- Gluteus maximus: Extends and externally rotates the hip, working against the rectus abdominis in trunk flexion.
- Hamstrings (biceps femoris, semitendinosus, semimembranosus): Flex the knee and extend the hip, counteracting the rectus abdominis during hip flexion.
COMMON INJURIES
- Rectus abdominis strain or tear: Caused by overstretching or excessive force, leading to pain and limited movement.
- Diastasis recti: A separation of the rectus abdominis muscles, often occurring during pregnancy or due to excessive abdominal pressure.
- Hernias: A protrusion of abdominal organs through a weakened area in the abdominal wall, causing pain and discomfort.
EXERCISES
- Crunches or sit-ups: Lie on your back and lift your upper body towards your knees, targeting the rectus abdominis. This exercise enhances core strength.
- Leg raises: Lie on your back and lift your legs to engage the lower rectus abdominis. This movement strengthens the lower abdominal muscles.
- Russian twists: Sit on the floor, lean back slightly, and rotate the torso side to side, engaging the rectus abdominis and obliques. Improves rotational strength.
- Bicycle crunches: Lie on your back and alternate elbow-to-knee touches, targeting the entire core. Enhances overall abdominal strength and coordination.
- Plank variations (e.g., plank with knee tucks): Hold a plank position and bring your knees towards your chest, engaging the rectus abdominis—which boosts core stability and endurance.
STRETCHES
- Cobra stretch: Lie on your stomach and lift your upper body with your hands, stretching the rectus abdominis. This stretch opens up the front of the body.
- Upward-facing dog pose: Similar to the cobra stretch, this yoga pose involves lifting the upper body and stretching the abdominal muscles.
- Child’s pose: Sit back on your heels with arms extended forward, stretching the entire back and abdominal region. Promotes relaxation and flexibility.
- Seated spinal twist: Sit with legs extended, cross one leg over the other, and twist the torso to stretch the rectus abdominis and obliques. Enhances spinal mobility.
- Standing backbend: Stand upright, place your hands on your lower back, and gently lean backward to stretch the abdominal muscles.