The side plank is a foundational bodyweight exercise designed to enhance core stabilization and strength. Unlike crunches, which focus on forward bending, the side plank challenges the body’s ability to resist lateral flexion (side-bending) and rotation. This isometric hold requires numerous muscle groups to work simultaneously to maintain a straight, rigid line from head to heels. The exercise is effective because it targets the lateral abdominal wall, which is often neglected in traditional core training. By setting the body against gravity in a side-lying position, the side plank provides a clear way to improve trunk stability and endurance.
Primary Muscles Targeted
The main muscles working to prevent the hips from collapsing toward the floor are the internal and external oblique muscles. These muscles form the body’s natural corset, running diagonally along the sides of the abdomen. The obliques on the side closest to the floor, known as the supporting side, engage intensely to create the necessary tension for the hold.
The external obliques are the superficial layer, while the internal obliques lie beneath them. In the side plank, these two layers on the supporting side contract strongly to prevent the trunk from dropping into a side-bend. This deep, sustained contraction is what makes the side plank a powerful anti-lateral flexion exercise. The rectus abdominis also works with the obliques to maintain a straight torso and prevent sagging of the lower back.
Deep Stabilizers and Secondary Support
Beyond the primary movers, the side plank relies heavily on several deep and smaller muscle groups for comprehensive stability.
Core and Hip Stabilizers
The Quadratus Lumborum (QL), a deep muscle in the lower back, plays a significant role by acting as a stabilizer to prevent excessive lateral tilt of the pelvis and spine. It runs from the top of the pelvis to the lower ribs and lumbar vertebrae, working alongside the obliques to maintain the straight body line. The Transverse Abdominis (TVA), the deepest layer of the abdominal wall, wraps around the midsection like a belt and isometrically contracts to provide circumferential stability to the trunk.
The Gluteus Medius, a muscle on the side of the hip, is also highly active, particularly on the bottom leg, to stabilize the pelvis and prevent the hips from rotating or dropping. This hip engagement is important for improving unilateral stability.
Shoulder Support
The supporting shoulder requires stability from the Deltoids and the Serratus Anterior. The Serratus Anterior presses the shoulder blade firmly against the rib cage, which prevents the shoulder joint from collapsing or shrugging toward the ear.
Proper Form to Engage the Core
To maximize muscle engagement in the side plank, proper setup is essential.
Setup
Begin by lying on your side with your elbow directly beneath your shoulder and your forearm flat on the ground, perpendicular to your body. Ensure your feet are stacked or staggered, with the top foot placed slightly in front of the bottom foot for a wider base of support. Your body should form a single, straight line from your head through your hips to your ankles.
Execution and Modification
The cue for initiating the hold is to lift the hips off the floor by actively pressing your forearm into the ground and squeezing your abdominal and gluteal muscles. Avoid the common mistake of letting your hips sag or rotate forward, which reduces the activation of the obliques and glutes. To maintain spinal alignment, think about tucking your pelvis slightly. If the full position is too challenging, a modification is to perform the exercise with the knees bent and using the bottom knee as the support point instead of the feet.