Which practice reduces stress on the lumbar during abdominal exercises?

• A. Extend the hips during crunches.
• B. Bend the knees during situps and crunches to reduce stress on the lumbar.
• C. Hold your breath during the movement.
• D. Lead with the chin during crunches.

Answer: (B)

Using knee bend reduces stress on the lumbar by shifting effort from the spine to the hips. When the knees are bent, hip flexors contribute more to lifting the torso, which allows the lumbar spine to stay in a more neutral position and decreases the lever arm that drives excessive spinal flexion. This lowers the compressive and shear forces on the lower back during situps and crunches. Extending the hips, holding the breath, or leading with the chin can increase lumbar load or create other risks, so bending the knees is the safer, more effective technique for protecting the lower back during these movements.