Understanding core integration is crucial for personal trainers aiming to help clients improve performance, reduce injury risk, and move with efficiency. One overlooked but highly insightful tool is a trunk flexion assessment—a simple test that provides a window into the relationship between deep and superficial core musculature, hip flexors, and neck flexors.

This blog breaks down how to perform the test, what to look for, common compensations, and how to progress clients who demonstrate dysfunction.

What Does the Test Assess?

This trunk flexion test evaluates the coordination and recruitment of the deep and superficial core muscles, particularly how they interact with the psoas and hip flexors during spinal flexion. It also offers insight into the function and compensation patterns of deep and superficial neck flexors, such as the sternocleidomastoid and scalenes.

How to Perform the Trunk Flexion Test

Client Setup:

• Client lies supine (on their back).

• Hands are pronated, resting on top of the upper thighs.

• Knees bent to 60–70 degrees.

• The practitioner places their hands under the client’s heels to monitor movement.

Execution:

• Instruct the client to perform a controlled sit-up, aiming to lift the scapulae off the table.

• Hold the top briefly, then lower under control.

• Watch for compensation patterns or loss of control.

Ideal Movement Pattern

In a properly functioning trunk flexion pattern:

• The abdominals contract and shorten, initiating spinal flexion.

• The lumbar spine flattens, and the pelvis posteriorly tilts.

• The heels remain in contact with the practitioner’s hands (indicating hip flexors are not dominating).

• The neck remains neutral, showing appropriate cervical alignment and no overuse of neck flexors.

Common Faults to Watch For

• Heels lifting off the hands: Indicates dominant or overactive hip flexors.

• Trunk lifts as a block: Lack of spinal flexion suggests poor abdominal engagement.

• Neck excessively flexed: Over-recruitment of deep neck flexors (e.g., longus colli) or superficial neck flexors(e.g., SCM, scalenes).

• Lack of posterior pelvic tilt: Anterior pelvic positioning maintained by tight hip flexors.

These faults reflect weakness or poor coordination of the core, and often appear in clients with chronic low back pain, poor movement efficiency, or those new to training.

Implications for Programming

If your client struggles with this test, it’s a red flag that they lack reflexive stability in their trunk and core musculature. This impacts their ability to:

• Control spinal position during loaded movements

• Breathe efficiently under tension

• Generate force in athletic or gym settings

The Fix: Start with Breath

Begin with nasal diaphragmatic breathing, which lays the foundation for reflexive deep core engagement. From here, you can build a progression model based on the client’s current capacity.

Core Progression Model for Trunk Flexion

Level 1: Reconnect and Reset

90/90 Breathing

• Restores diaphragmatic function, pelvic alignment, and abdominal awareness.

• Sets the tone for integrating breath with movement.

Level 2: Integrate Limbs with Core

Dead Bug with Contralateral Arm and Leg

• Develops coordinated control between upper and lower extremities.

• Reinforces trunk stability in a supine, low-risk position.

Dead Bug with Band

• Adds hip flexor loading in a controlled environment.

• Trains hip and trunk co-activation without compensation.

Level 3: Load and Challenge

Half Get-Up

• Encourages asymmetrical core control and shoulder stability under partial load.

• Bridges floor-based training with upright function.

Turkish Get-Up

• High-value compound pattern integrating:

  • Core flexion

  • Shoulder strength

  • Hip extension

  • Lunge mechanics

• Ideal for advanced clients or athletic populations.

Final Thoughts for Coaches

This test is simple but powerful. It highlights not just what muscles are weak, but how your client compensates—and that’s the information you need to coach them more effectively. Integrate it into your assessment system and use the progression model to build a more resilient, reflexively stable core in your clients.

Stay tuned for follow-up posts where we explore core extension, rotation patterns, and anti-movement assessments—helping you round out your screening toolbox.