Sahrmann Core Stability Test

What is the Sahrmann Core Stability Test?

The Sahrmann Core Stability Test (CST) is a 5-level progressive clinical assessment developed by Shirley Sahrmann (2002) to evaluate lumbo-pelvic motor control — specifically the ability to maintain a neutral spine position while progressively loading the hip flexors through limb movement. Unlike traditional abdominal strength tests, the Sahrmann test assesses neuromuscular control and movement dissociation, not raw muscle force. It targets the deep stabilizing muscles — Transversus Abdominis (TrA), multifidus, and pelvic floor — that are frequently inhibited in patients with low back pain.

Why the Sahrmann Test Matters for Low Back Pain

Research by Richardson, Jull, and colleagues (1999) demonstrated that in patients with low back pain, the TrA loses its normal anticipatory activation pattern — it no longer fires before limb movement to pre-stiffen the spine. Instead, patients substitute global mobilizer muscles (rectus abdominis, hip flexors) which create segmental compression and shear rather than stabilization. The Sahrmann test directly reveals these substitution patterns: if a patient cannot maintain the PBU at 40 mmHg while performing Level 1, they are demonstrating exactly this failure of deep stabilizer activation.

The 5 Sahrmann Levels Explained

• Level 1 — Unilateral Heel Slide: The easiest level. Patient slides one heel along the surface from 90° hip/knee flexion to full extension. If the spine extends into the table or the pelvis tilts, Level 1 is failed. Failing this level in the clinic is a strong indicator of instability-related LBP.
• Level 2 — Unilateral Leg Lift (Marching): From 90° flexion, lift one foot 6–8 cm off the surface. The unsupported leg creates an eccentric hip flexor demand. PBU often rises at this level as patients posteriorly tilt to compensate.
• Level 3 — Single Leg Lowering to 45°: Lower one leg from 90° to 45° hip flexion (knee extended or flexed). This demands sustained eccentric control of one hip flexor group while the core maintains neutral.
• Level 4 — Double Leg Lowering to 45°: Both legs lower simultaneously from table-top position to 45°. Doubles the eccentric hip flexor demand. Most sedentary adults fail at this level, and Valsalva breath-holding becomes common.
• Level 5 — Double Leg Lowering to Surface: Full range bilateral leg lowering from 90° to 0° hip flexion. Maximum eccentric hip flexor load. Only well-trained athletes with strong lumbo-pelvic motor control pass this level consistently.

Using the Pressure Biofeedback Unit (PBU)

The PBU is a small inflatable pressure cuff placed under the lumbar spine. It is inflated to 40 mmHg as the standard baseline. During the test, the clinician monitors the pressure gauge:

• Pressure drops below 30 mmHg: Patient is allowing the lumbar spine to extend (anterior pelvic tilt) — hip flexors are pulling the pelvis forward and the TrA is not controlling it.
• Pressure rises above 50 mmHg: Patient is posteriorly tilting the pelvis (flattening the lumbar spine) — substituting rectus abdominis for deep stabilizers.
• Pressure stays at 40 ±10 mmHg: Pass — neutral spine maintained through the movement.

Motor Control Faults and Their Meaning

• Valsalva breath-holding: Patient is using global IAP strategy — unable to selectively recruit TrA without holding breath. Common at Levels 4–5.
• Increased lumbar lordosis: Hip flexors are dominating, anterior pelvic tilt increasing, TrA failing to prevent lumbar extension. Common at Levels 1–2 in LBP patients.
• Hip flexor dominance: Patient is contracting iliopsoas excessively instead of co-activating TrA and multifidus as the primary stabilizers.
• Posterior pelvic tilt: Rectus abdominis substitution — patient is flattening the lumbar spine (flexing) rather than maintaining neutral. Seen at Levels 3–4.
• Rib flare: Loss of lower ribcage apposition — diaphragm and TrA not coordinating in a pressure canister pattern.

Clinical Applications

• Low back pain screening — Identifies patients with instability-pattern LBP who need motor control rehabilitation rather than strengthening
• Return-to-sport clearance — Athletes must achieve Level 4–5 before returning to high-load activities
• Post-partum rehabilitation — Assesses diastasis recti and pelvic floor-TrA coordination in post-natal patients
• Pre-operative assessment — Baseline motor control documentation before lumbar spine surgery
• Exercise prescription — The highest failed level becomes the first training target — systematic progressive loading

Sahrmann Test vs Other Core Assessments

• vs Plank test: Plank measures static trunk endurance; Sahrmann measures dynamic motor control during limb movement. Both assess core function but different components — use together for comprehensive core evaluation.
• vs FMS Trunk Stability Push-Up: FMS item 6 tests reflexive stabilization in the sagittal plane; Sahrmann tests progressive eccentric hip flexor control. FMS is a screen; Sahrmann is a diagnostic tool.
• vs Dead Bug exercise assessment: The Dead Bug exercise is the therapeutic application of the Sahrmann principle — use Sahrmann to assess, Dead Bug to train.