Make sure you have a proper form:
- Sit your hips back as far as possible into both the back pad and seat pad. Sitting back will center your butt and pelvis in the seat and reduce the likelihood of any unwanted pelvic shifting during the dynamic movement.
- Position the abdominal pad just below the level of your sternum to create the right length lever arm.
- your starting spinal position should be in slight extension. Though this position is unique to every body type, you can find it by first getting yourself into neutral posture and then arching your thoracic and upper lumbar spine slightly.
- Do a crunch in a slow controlled manner while slowly breathing out.
- Pause at the bottom of your crunch for a second and return to the starting position
Make sure to use weight you can handle, choosing too much weight can easily cause injury.