Lying leg raises, often called “leg ups,” are a foundational core exercise designed to build strength and stability throughout the midsection. This bodyweight movement specifically targets the rectus abdominis, the long muscle running vertically along the front of the abdomen. Executing the movement with precision, rather than speed, maximizes the benefit and avoids potential strain. This guide covers proper form, muscle engagement, common errors, and scaling the exercise.
Executing the Basic Movement
To begin the lying leg raise, position yourself flat on your back on a mat, extending both legs straight out. Place your arms alongside your body with palms pressed firmly into the floor for a stable base. Engage your abdominal muscles by gently pulling your navel toward your spine to ensure your lower back remains flat against the floor.
The lifting phase starts by slowly raising both legs simultaneously, keeping them as straight as possible throughout the movement. Exhale steadily as your legs travel upward, aiming for a 90-degree angle where your heels are directly above your hips. The lift must be controlled solely by the core muscles, avoiding swinging or using momentum.
The lowering phase is the most demanding part, maximizing the time the muscles spend under tension. Inhale slowly while lowering your legs back toward the starting position with deliberate control. Resist dropping the legs quickly, instead taking at least two to three seconds for the descent. Stop just before your heels touch the floor, maintaining abdominal tension before initiating the next repetition.
Primary Muscle Engagement
The leg raise relies on a synergistic effort between the abdominal muscles and the hip flexors to perform the complex movement. The rectus abdominis acts to prevent the pelvis from tilting forward as the weight of the legs increases the load on the core. This anti-extension function provides the intense contraction often felt in the lower abdominal region during the lift.
The primary movers responsible for bringing the legs upward are the hip flexors, particularly the iliopsoas group. These deep muscles connect the lumbar spine and pelvis to the femur, facilitating hip joint flexion. The transverse abdominis also plays a stabilization role, acting like a natural corset to brace the spine and maintain a flat lumbar curve against the floor.
The quality of the repetition depends on the balance of these muscle groups. The hip flexors lift the legs, while the deep core muscles stabilize the torso. Without adequate core strength, the hip flexors can dominate, leading to a loss of form and subsequent lower back strain.
Common Form Errors and Corrections
One frequent error is allowing the lower back to arch off the floor as the legs are lowered. This lumbar hyperextension shifts the load away from the core and places unnecessary, and potentially harmful, stress on the lumbar spine and its discs. To correct this, actively press your lower back into the floor before starting the set. Only lower your legs as far as you can maintain this flat back position.
Another common fault is relying on momentum, or “swinging,” to initiate the lift. This turns the exercise into a hip-driven movement instead of controlled core engagement. If you rock your body to lift your legs, the weight is likely too heavy for your current core strength. Slow the entire repetition down, especially the descent, to ensure the muscles dictate the pace.
Tension in the neck and shoulders can occur when straining to compensate for a lack of abdominal strength. Ensure your hands press into the floor and your chin is slightly tucked to keep the neck neutral and aligned with the spine. If maintaining a neutral neck is difficult, a small, rolled-up towel can be placed under the head for support.
Progression and Variation
If the straight-leg version is too challenging, regressing the movement is the best path to building foundational strength without compromising form. The Bent-Knee Leg Raise is an excellent modification. The knees are kept bent at a 90-degree angle, significantly shortening the lever arm and reducing the load on the core. Placing hands flat under the glutes can also offer slight pelvic support, helping prevent the lower back from arching.
Once the basic straight-leg lift can be performed with control for multiple repetitions, progression can be introduced. Increasing the time under tension by taking four or five seconds for the lowering phase is an effective way to add intensity. Introducing a light weight, such as a small dumbbell held between the feet, further increases the resistance the core must stabilize.
For a more advanced challenge, the exercise can be moved into a Hanging Leg Raise, where the body is suspended from a pull-up bar. This variation requires greater grip strength and challenges the core to stabilize the entire body against gravity. The most difficult progression is the Toe-to-Bar, which demands that the straight legs be raised high enough to touch the bar, requiring maximum abdominal contraction.