Crunch (Bodyweight)
Also called Crunch
How to do it
Lie on your back with knees bent and feet flat. Exhale as you curl the ribs toward the hips and lift only the shoulder blades from the floor, pause briefly, then lower slowly until the upper back returns without relaxing the abdominal brace. Keep the range shorter than a sit-up.
Setup
Lie with feet flat and knees bent around 90 degrees. Cross the arms over the chest or place fingertips lightly beside the head without pulling the neck, and gently flatten the ribs.
Where you should feel it
Across the front abdominal wall as the ribs curl toward the pelvis, with the obliques assisting. The neck and hip flexors should not dominate.
When to use it
Use for foundational trunk-flexion control and abdominal endurance with no equipment. Slow sets of 10-25 reps work well.