Mermaid Crunches: Understanding, Benefits, and Proper Execution

What are mermaid crunches?

Mermaid crunches are a specialized core exercise that primarily targets the oblique muscles, promoting lateral spinal flexion and enhancing side-body strength and stability. Unlike traditional crunches, they are performed in a side-lying position, emphasizing unilateral core engagement and spinal mobility.

Understanding the Mermaid Crunch

The mermaid crunch is a dynamic, bodyweight exercise celebrated for its effectiveness in isolating and strengthening the oblique muscles—the muscles responsible for side-bending and trunk rotation. It deviates from standard crunch variations by moving the body in the coronal (frontal) plane, specifically focusing on lateral flexion of the spine. This unique movement pattern makes it an excellent addition to a comprehensive core training regimen, offering benefits beyond typical flexion-based abdominal exercises.

Anatomy and Biomechanics: Muscles at Work

Performing a mermaid crunch engages a specific set of muscles to execute the lateral spinal flexion and stabilize the trunk.

• Primary Movers (Agonists):
  • External Obliques: These superficial abdominal muscles run diagonally downwards and forwards. They are crucial for contralateral rotation and ipsilateral lateral flexion of the trunk.
  • Internal Obliques: Lying beneath the external obliques, these muscles run diagonally upwards and forwards. They are primary contributors to ipsilateral rotation and ipsilateral lateral flexion of the trunk.
  • Quadratus Lumborum: Located in the lower back, this muscle assists in lateral flexion of the lumbar spine and hip hiking.
• Synergists and Stabilizers:
  • Transverse Abdominis (TrA): The deepest abdominal muscle, it acts as a natural corset, stabilizing the lumbar spine and pelvis, particularly important during unilateral movements.
  • Rectus Abdominis: While not the primary mover, it assists in stabilizing the trunk and may contribute minimally to flexion if the movement extends beyond pure lateral flexion.
  • Erector Spinae: These muscles along the spine work to stabilize the vertebral column and control the eccentric (lowering) phase of the movement.
  • Hip Abductors/Adductors: Depending on the leg position, these muscles may provide stabilization.

The mermaid crunch primarily involves lateral flexion of the spine, where the trunk bends to the side. The movement is initiated by the contraction of the obliques on the side of the body that is lifting, drawing the rib cage closer to the hip.

How to Perform Mermaid Crunches Correctly

Executing mermaid crunches with precision is key to maximizing their benefits and preventing strain.

1. Starting Position:
   • Lie on your side on a mat, with your body in a straight line from head to heels.
   • Stack your legs directly on top of each other, or for more stability, bend your knees slightly and stack them.
   • Place your bottom arm extended along the floor overhead, or bent and supporting your head.
   • Place your top hand either on the floor in front of your chest for support, or behind your head with the elbow pointing towards the ceiling.
   • Ensure your hips are stacked, and your core is gently engaged to prevent sagging.
2. The Movement (Concentric Phase):
   • Exhale as you simultaneously lift your upper body (rib cage) and your legs off the floor, bringing them towards each other in a C-shape.
   • Focus on contracting your top-side oblique muscles to initiate and drive the movement.
   • Aim to lift both your shoulders and your feet a few inches off the floor.
   • Maintain control throughout the lift, avoiding jerky movements.
3. Descent (Eccentric Phase):
   • Inhale as you slowly and deliberately lower your upper body and legs back to the starting position.
   • Control the descent to fully engage the muscles and prevent gravity from taking over.
   • Avoid collapsing onto the mat; maintain tension as you return.
4. Repetitions:
   • Complete your desired number of repetitions on one side before switching to the other side to ensure balanced development.

Benefits of Incorporating Mermaid Crunches

Adding mermaid crunches to your routine offers several distinct advantages for core health and overall physical performance.

• Targeted Oblique Development: They provide a direct and highly effective way to strengthen the external and internal obliques, which are often undertrained compared to the rectus abdominis. This contributes to a more sculpted waistline and improved rotational power.
• Enhanced Core Stability: Strong obliques are crucial for stabilizing the trunk during lateral movements, preventing unwanted side-bending, and protecting the spine from injury.
• Improved Spinal Mobility: The lateral flexion movement gently mobilizes the spine in the frontal plane, which can improve overall spinal health and flexibility.
• Better Posture: A strong, balanced core, including robust obliques, supports proper spinal alignment and helps maintain an upright posture.
• Functional Strength: Lateral flexion is a fundamental movement pattern used in daily activities (e.g., reaching sideways, picking up objects) and many sports (e.g., throwing, swinging, changing direction). Strengthening this movement translates directly to improved functional fitness.
• Unilateral Core Training: As a unilateral exercise, it helps identify and correct muscular imbalances between the left and right sides of the core.

Common Mistakes to Avoid

To maximize effectiveness and minimize injury risk, be mindful of these common errors.

• Relying on Momentum: Using a swinging motion or momentum to lift the body rather than controlled muscular contraction reduces the exercise's effectiveness.
• Insufficient Range of Motion: Not fully engaging the obliques by taking the movement through its complete range (both the lift and the controlled descent).
• Neck Strain: Pulling on the neck with the top hand or allowing the head to flop can lead to discomfort. Keep the neck in line with the spine.
• Holding Your Breath: Proper breathing (exhaling on exertion, inhaling on release) helps engage the core and maintain intra-abdominal pressure.
• Ignoring Both Sides: Always perform an equal number of repetitions on both sides to prevent muscular imbalances.
• Loss of Hip Stack: Allowing the top hip to roll forward or backward can reduce oblique engagement and put undue stress on the lower back.

Variations and Progression

Once you've mastered the basic mermaid crunch, you can explore variations to increase the challenge or modify the exercise.

• Assisted Mermaid Crunch: For beginners, keep the bottom arm extended along the floor for additional support during the lift.
• Hands Behind Head: Placing both hands behind the head (similar to a traditional crunch) increases the lever arm and makes the exercise more challenging by requiring more core strength to lift the upper body.
• Weighted Mermaid Crunch: Holding a light dumbbell or weight plate on the top hip or across the chest can add resistance, progressing the exercise.
• Mermaid Crunch on a Stability Ball: Performing the exercise with your side draped over a stability ball increases the range of motion and challenges core stability due to the unstable surface.

Who Can Benefit?

Mermaid crunches are beneficial for a wide range of individuals:

• Fitness Enthusiasts: Those looking to diversify their core routine and specifically target the obliques.
• Personal Trainers and Student Kinesiologists: A valuable exercise to teach for comprehensive core development and understanding lateral flexion.
• Athletes: Particularly those involved in sports requiring rotational power (e.g., golf, tennis, baseball) or quick changes of direction.
• Individuals Seeking Core Stability: Anyone aiming to improve overall trunk stability, posture, and reduce lower back pain.

Conclusion

The mermaid crunch is an excellent, often overlooked, exercise for developing strong, stable, and mobile obliques. By understanding its biomechanics, practicing correct form, and being mindful of common mistakes, you can effectively integrate this movement into your fitness regimen. Prioritizing unilateral core strength and lateral spinal mobility through exercises like the mermaid crunch contributes significantly to a well-rounded, functional, and resilient core.