The lying leg raise is a challenging yet highly effective bodyweight exercise performed while lying face-up on the floor. This movement strengthens the lower abdominal wall and improves hip joint mobility. When executed with proper form, the exercise creates a long lever arm with the legs, demanding substantial control from the trunk muscles. This difficulty makes it a powerful tool for developing core strength and stability.
Primary Muscle Groups in Action
The lifting of the legs is primarily driven by the hip flexors, a powerful group of muscles located deep within the pelvis and upper thigh. The iliopsoas, formed by the psoas major and the iliacus, is the main engine responsible for hip flexion. It pulls the femur toward the torso, raising the legs from the floor. The rectus femoris, one of the quadriceps muscles, also crosses the hip joint and contributes to this lifting motion.
Although the movement is initiated by the hip flexors, the core muscles manage the forces created by the long lever of the legs. The rectus abdominis, commonly known as the “six-pack,” works to flex the spine and prevent the pelvis from tilting forward. This forward tilt, called an anterior pelvic tilt, is a natural response to the hip flexors pulling on the spine. The rectus abdominis must contract to keep the torso and pelvis stable against the upward motion.
The Critical Role of Stabilizing Muscles
The deeper, stabilizing muscles of the trunk must engage to protect the lower back. The transverse abdominis (TVA) is a deep muscle that acts like a natural corset, creating intra-abdominal pressure. Bracing the core with the TVA is necessary to maintain a neutral or slightly posteriorly tilted pelvis against the strong forces exerted by the hip flexors.
Without sufficient TVA activation, the lower back arches excessively, placing strain on the lumbar vertebrae. The internal and external obliques, located on the sides of the torso, also function as stabilizers. They assist the rectus abdominis in preventing unwanted rotation or side-to-side movement, ensuring the core remains rigid throughout the range of motion.
Executing the Lying Leg Raise Safely
To begin, lie on the floor with the legs extended and the arms placed at the sides, palms down for support. Gently press the lower back flat against the floor, achieving a slight posterior pelvic tilt before any movement starts.
With the core braced, slowly lift the legs toward the ceiling in a controlled manner, maintaining straight knees. The movement should be smooth and deliberate, originating from the hips rather than swinging the legs. The greatest challenge comes during the descent, where gravity works against the core. Lower the legs slowly back toward the floor, stopping just before the lower back begins to lift or arch off the ground.
Adjusting Difficulty and Avoiding Lower Back Strain
Lower back discomfort is common and indicates that the hip flexors are overpowering the core stabilizers. The long lever created by straight legs puts immense pressure on the core to maintain spinal position. If the stabilizing muscles are not strong enough, the pelvis tilts forward, causing the lower back to arch.
Several modifications can be used to adjust difficulty and build strength safely:
- Perform the bent-knee variation, which significantly shortens the lever arm and reduces the load on the core.
- Reduce the range of motion by only lowering the legs halfway down before immediately raising them again.
- Focus on the lowering phase only, known as a negative repetition.
- Use the hands to help lift the legs up, then slowly control the descent only to the point where the lower back remains pressed to the floor.