I know that your abs, and rectus abdominal, are one muscle, but you need to think of them as 2.
The upper half and the lower. I see many people trying to train abs with one motion, and it isn't going to work out that well for you. Remember that every muscle has an origin and insertion point.
Usually, a muscle only works on one joint outside the hamstring, which works 2. To be fair to working the hamstring, we normally work the different parts of the hamstring differently, whether we know it or not. However, if you want excellent abdominal function and look, you must train the upper and lower half separately.
Some of the best exercises for this is using weighted ab pulldowns.
You do this by holding the weight from a cable and crunching it down. You pull your ribs into your pelvis and curl up into a ball. It is a good exercise for the upper and mid portion of the abs. However, to work the midsection and the lower, the best way to do this is with a roman chair or hanging pelvic raises.
Most of us have legs and feet that weigh enough to make this exercise functional and hard. Remember, lifting the legs isn't the goal. Lifting the bottom of the pelvis is the goal.
I see many people flailing their legs around from the hip but not pulling the bottom of the pelvis, the pubic symphysis up towards their ribs. When training abs you need to pull the ribs down to the pelvis and the pubic symphysis up to the ribs. I have seen people have back pain when they do not do this because they overdevelop the upper abs and don't develop much lower portion.
The problem is that the abs move so many joints that you have to attack the muscle in 2 parts, or you will never produce the motion you need to activate it properly.
Check out Chalmers Pillarsofwellness.com for Wellness updates! And ask me any questions you have at questions@chalmerswellness.com. I answer all of them and look forward to hearing from you.
The Chalmers Wellness Stubstack just launched. Comment, Like, Interact with other people on their wellness journey. Communities can make the difference.    DrChalmers.substack.com
Dr. Matt Chalmers
Disclaimer: This content is for informational purposes only. Before taking any action based on this information you should first consult with your physician or health care provider. This information is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health providers with any questions regarding a medical condition, your health, or wellness.