The scissor kick is a dynamic core exercise performed while lying on the back, involving the controlled, alternating up-and-down or criss-cross movement of the legs. Scissor kicks are effective for building core endurance and stability when performed correctly. However, the mechanics are often misunderstood, leading to form errors that minimize abdominal engagement. The exercise relies entirely on the core’s ability to stabilize the spine against the leverage created by the moving legs.
The Primary Muscles Engaged
Scissor kicks primarily recruit the core muscles for stabilization. This includes the rectus abdominis, which is the long muscle that forms the “six-pack” and is responsible for flexing the trunk, and the deep-lying transverse abdominis, which stabilizes the spine. Both muscles are engaged to prevent the lower back from arching away from the floor.
The actual movement of the legs is powered mainly by the hip flexors, including the iliopsoas, which connects the leg to the lower spine and pelvis. The scissor motion emphasizes the hip flexors because the extended legs create a long lever arm. The core muscles must work intensely to counteract the pull these prime movers exert on the lumbar spine.
Proper Scissor Kick Technique
To maximize abdominal engagement, begin by lying supine with the lower back pressed into the mat to ensure a neutral spine position. Hands should be placed flat alongside the body or tucked palms-down underneath the glutes for increased support.
Both legs are lifted slightly off the floor, typically to an angle of about 45 degrees. From this starting position, the legs alternate in a controlled, rhythmic scissoring motion, moving up and down or side to side. The movement should be slow and deliberate, focusing on maintaining a tight core to keep the lower back anchored to the floor throughout the set. Breathing should be continuous, avoiding the tendency to hold the breath.
Preventing Lower Back Discomfort
A common risk with scissor kicks is lumbar hyperextension, or arching of the lower back. This arching occurs when the core muscles are not strong enough to stabilize the spine against the downward pull exerted by the hip flexors and the weight of the extended legs. The inability to maintain a posterior pelvic tilt—a slight tucking of the pelvis—shifts the workload from the abdominals to the vulnerable lumbar spine.
To prevent this, consciously press the lower back into the floor for the entire duration of the exercise. Beginners should reduce the range of motion by keeping the legs higher, perhaps at a 60-degree angle, or by making the scissoring movement smaller. Bending the knees slightly also shortens the lever arm of the legs, making it easier for the core to maintain spinal neutrality until strength improves.
Integrating Scissor Kicks Into a Core Routine
Scissor kicks are categorized as a dynamic anti-extension exercise, where the core’s primary function is to prevent the trunk from extending, or arching, under the load of the moving limbs. This distinguishes them from static exercises like planks, which are isometric holds, or flexion exercises like crunches, which involve spinal movement. They are effective for improving muscular endurance because the core is held under continuous tension for the duration of the set.
For optimal integration, scissor kicks should typically be placed later in a core training session, after compound movements and basic stabilization exercises. A standard recommendation is to perform them for a set duration, such as 30 to 60 seconds, or for a high number of repetitions, completing two to three sets per session. This focus on time-under-tension and endurance helps improve overall stability and posture.