In trunk extensor testing, which region should be stabilized to isolate the trunk?

In trunk extensor testing, which region should be stabilized to isolate the trunk?

• A. Head
• B. Pelvis
• C. Shoulders
• D. Feet

Answer: (B)

Isolating the trunk extensors requires anchoring the pelvis so that the movement comes from the spine itself, not from the hips. When you stabilize the pelvis during trunk extensor testing, you prevent substitution from hip extension or pelvic tilt via the glutes and hamstrings. This forces the spinal erectors to do the work, giving a true measure of trunk extensor strength. Stabilizing other regions like the head, shoulders, or feet won’t stop those hip-driven substitutions, so they’re less effective at isolating the trunk. In practice, you would secure the pelvis (for example with a hand on the ASIS area or a belt/strap) while the patient extends the trunk against resistance applied to the upper back or shoulders.

Isolating the trunk extensors requires anchoring the pelvis so that the movement comes from the spine itself, not from the hips. When you stabilize the pelvis during trunk extensor testing, you prevent substitution from hip extension or pelvic tilt via the glutes and hamstrings. This forces the spinal erectors to do the work, giving a true measure of trunk extensor strength. Stabilizing other regions like the head, shoulders, or feet won’t stop those hip-driven substitutions, so they’re less effective at isolating the trunk. In practice, you would secure the pelvis (for example with a hand on the ASIS area or a belt/strap) while the patient extends the trunk against resistance applied to the upper back or shoulders.