The hanging leg raise is a demanding bodyweight exercise often performed to develop the abdominal muscles. Many people believe it specifically targets the “lower abs,” an idea that persists in the fitness world. This exercise is effective for challenging the entire core, but the technique used dictates which muscles perform the majority of the work. Understanding the anatomy and mechanics of leg lifting is essential to maximizing its effectiveness.
Understanding the Rectus Abdominis
The rectus abdominis is the long, flat muscle that runs vertically from the lower rib cage and sternum down to the pubic bone. Despite its common appearance as a “six-pack” or “eight-pack,” created by horizontal bands of connective tissue called tendinous intersections, it is a single sheet of muscle. This muscle’s primary function is to flex the trunk, such as when performing a crunch, bringing the rib cage closer to the pelvis or vice versa.
The concept of isolating an upper or lower section of the rectus abdominis is anatomically inaccurate. A muscle contracts as a single unit, meaning the entire muscle is engaged when activated. However, the feeling of a lower abdominal workout is often generated because the muscle’s insertion point is on the pelvis. When the rectus abdominis contracts to move the pelvis towards the rib cage during a leg raise, tension is naturally felt most strongly near that lower attachment point.
The muscle’s role in a hanging leg raise is to create spinal flexion, which is the curling of the lower spine and the posterior rotation of the pelvis. If the movement is performed without this curling action, the rectus abdominis acts primarily as an isometric stabilizer rather than a dynamic mover. Core engagement depends entirely on the extent of this pelvic and spinal movement.
The Role of Hip Flexors in Leg Raising
In a standard hanging leg raise, the mechanical action of lifting the legs is primarily driven by the hip flexor group. The main hip flexors are the iliopsoas, a combined group of the psoas major and the iliacus muscles. These muscles originate on the lumbar spine and pelvis and insert onto the femur, making them responsible for drawing the legs upward toward the torso.
If the hanging leg raise is performed by simply lifting the legs without curling the spine, the iliopsoas and other hip flexors are the prime movers. In this scenario, the abdominal muscles contract statically to prevent the torso from swinging or the lower back from excessively arching. This is why many individuals new to the exercise report feeling a burning sensation in their hips rather than their abdominal muscles.
The psoas muscle connects directly to the lumbar vertebrae and is heavily recruited during hip flexion. When the legs are lifted past a certain point, the hip flexors naturally try to pull the pelvis forward into an anterior tilt. The abdominal muscles must fight against this pull to maintain a neutral spine or, ideally, to curl the spine, which is the key to activating the core.
Technique Adjustments for Core Engagement
To ensure the hanging leg raise effectively targets the rectus abdominis rather than becoming a hip flexor exercise, the technique must emphasize spinal flexion. The movement should be initiated by a posterior pelvic tilt, which means tilting the tailbone slightly forward and curling the lower back. This action forcefully engages the abdominal muscles to bring the pelvis up toward the rib cage.
Instead of thinking about lifting the feet, the focus should be on curling the hips off the vertical line and bringing the knees toward the chest or shoulders. This deliberate rounding of the lower back ensures the abdominal muscles are the primary drivers of the movement. Maintaining a slow, controlled pace is necessary, particularly on the descent, to avoid using momentum.
Beginners can start with a bent-knee variation, often called a hanging knee raise, because the shorter lever arm decreases the resistance and demand on the hip flexors. As strength increases, the legs can be straightened, which significantly increases the leverage and challenge for the abdominal muscles. The most effective core engagement occurs when the legs are lifted high enough to create a distinct and visible rounding of the lumbar spine.