Obliques: Anatomy, Function, and Training for Your Side Abs

What is the Muscle on the Side of the Abs?

The primary muscles on the side of the abdominal region are the oblique muscles, specifically the external obliques and internal obliques, which are crucial for spinal rotation, lateral flexion, and overall core stability.

Introduction to the Core and Abdominal Wall

The "abs" or abdominal muscles are a complex group forming the anterior and lateral walls of the human trunk. While the rectus abdominis (the "six-pack" muscle) runs vertically down the front, the muscles responsible for the prominent contours and functional movements on the sides of your midsection are primarily the obliques. These muscles are essential not only for aesthetics but, more importantly, for dynamic movement, spinal stability, and power generation.

The Oblique Muscles: Your Lateral Powerhouses

The oblique muscles are a pair of broad, flat muscles located on each side of the trunk, forming the lateral part of the abdominal wall. They are arranged in layers, with their fibers running in opposing directions, which allows for complex multi-planar movements.

External Obliques

The external oblique is the largest and most superficial of the abdominal muscles.

• Anatomy: It originates from the lower eight ribs, interdigitating with the serratus anterior and latissimus dorsi. Its fibers run inferomedially (downward and inward), similar to putting your hands in your pockets.
• Insertion: It inserts into the iliac crest (top of the hip bone), the pubic tubercle, and a broad aponeurosis (sheet-like tendon) that forms the anterior abdominal wall, contributing to the linea alba (midline tendon).
• Function:
  • Bilateral Contraction (both sides): Flexes the vertebral column (e.g., crunches).
  • Unilateral Contraction (one side):
    • Laterally flexes the trunk to the same side.
    • Rotates the trunk to the opposite side (e.g., left external oblique rotates the trunk to the right).

Internal Obliques

The internal oblique lies deep to the external oblique, forming the middle layer of the lateral abdominal wall.

• Anatomy: It originates from the thoracolumbar fascia (lower back connective tissue), the iliac crest, and the lateral two-thirds of the inguinal ligament. Its fibers run superomedially (upward and inward), perpendicular to the external oblique fibers.
• Insertion: It inserts into the cartilages of the lower three to four ribs, the pubic crest, and the linea alba.
• Function:
  • Bilateral Contraction: Flexes the vertebral column.
  • Unilateral Contraction:
    • Laterally flexes the trunk to the same side.
    • Rotates the trunk to the same side (e.g., left internal oblique rotates the trunk to the left).

The opposing fiber directions and rotational actions of the external and internal obliques mean that for a trunk rotation to the right, the right internal oblique and the left external oblique work synergistically.

Beyond the Obliques: Other Lateral Core Stabilizers

While the obliques are the primary "side abs," other muscles contribute significantly to lateral trunk stability and movement.

Transversus Abdominis (TVA)

Deep to the internal obliques lies the transversus abdominis.

• Role: While not strictly on the "side" in a superficial sense, its fibers run horizontally, acting like a natural corset. It is crucial for increasing intra-abdominal pressure, stabilizing the lumbar spine, and providing a foundation for all other core movements. Its deep stabilizing action significantly supports the lateral abdominal wall.

Quadratus Lumborum (QL)

Located in the posterior abdominal wall, the quadratus lumborum also plays a role in lateral trunk movement.

• Role: It connects the iliac crest to the lower ribs and lumbar vertebrae. Its primary actions are lateral flexion of the trunk (especially hip hiking) and stabilization of the lumbar spine. While more of a back muscle, its lateral position and function contribute to the overall lateral trunk system.

Why Strong Obliques Matter

Developing strong and functional obliques extends far beyond achieving a desirable physique. They are fundamental for:

• Spinal Stability and Injury Prevention: The obliques act as dynamic stabilizers for the lumbar spine, protecting it from excessive rotational and lateral shearing forces, which are common causes of lower back pain.
• Rotational Power and Athletic Performance: Most sports involve powerful rotational movements (e.g., swinging a golf club, throwing a ball, punching). Strong obliques are crucial for generating and controlling this rotational force, improving athletic performance.
• Posture and Aesthetics: Well-developed obliques contribute to a stable and upright posture. Aesthetically, they help define the waistline and contribute to the "V-taper" appearance for those with lower body fat percentages.
• Everyday Function: Simple movements like twisting to grab something, getting out of bed, or carrying groceries rely heavily on oblique strength and coordination.

Training Your Obliques Effectively

Effective oblique training focuses on their primary functions: rotation, lateral flexion, and anti-movement (resisting rotation and lateral flexion).

Key Training Principles

• Controlled Movement: Avoid fast, jerky movements that rely on momentum. Focus on slow, controlled contractions.
• Full Range of Motion: Work through the muscle's complete range of motion where appropriate.
• Anti-Rotation and Anti-Lateral Flexion: Incorporate exercises that challenge your core's ability to resist unwanted movement, which is highly functional.

Sample Exercises for Oblique Development

• Side Plank: Excellent for anti-lateral flexion and isometric strength. Hold for time, focusing on maintaining a straight line from head to heels.
• Cable Chops/Lifts: Dynamic exercises that train rotational power and anti-rotation. Perform slowly and controlled.
• Bicycle Crunches: A classic exercise that combines spinal flexion and rotation. Focus on bringing the opposite elbow to the knee, emphasizing the twist.
• Russian Twists (controlled): Sit with knees bent, feet elevated or on the floor. Rotate the torso from side to side, ensuring the movement comes from the core, not just the arms. Adding a medicine ball or weight can increase intensity.
• Pallof Press: An anti-rotation exercise using a cable machine or resistance band. Stand perpendicular to the cable and press the handle straight out, resisting the urge to rotate.
• Side Bends (with caution): Can be performed with a dumbbell, but emphasize slow, controlled movement and avoid excessive weight to prevent spinal compression. Focus on lateral flexion.

Common Mistakes and Considerations

• Over-reliance on Spinal Flexion: Many "ab" exercises focus solely on crunching. Incorporate rotational and anti-movement exercises to ensure comprehensive oblique development.
• Ignoring Anti-Movement: Training your obliques to resist movement (e.g., anti-rotation, anti-lateral flexion) is often more functional and protective for the spine than solely performing dynamic rotations.
• Focusing Solely on Aesthetics: While strong obliques look good, prioritize their functional role in stability and movement to ensure a healthy, resilient core.
• Improper Form: Sacrificing form for speed or weight can put undue stress on the spine. Always prioritize controlled, precise movements.

Conclusion

The muscles on the side of your abs are predominantly the external and internal obliques, supported by the deeper transversus abdominis and the quadratus lumborum. These muscles are indispensable for spinal stability, rotational power, lateral flexion, and maintaining good posture. Integrating a balanced training program that targets their full range of functions—flexion, rotation, lateral flexion, and anti-movement—is crucial for a resilient, high-performing core and overall physical well-being.