The best way to train the abs in my opinion is by forcing them to work. Reflexive training is nothing new, but not used enough. I have many patients that are constantly asking me how to get their lower abs stronger.
One of the many dysfunctions I see is the psoas muscle substituting for the lower abs. This is really common in people that do pilates or gym goers that do lots of hanging leg raises.
Enter the Pulsed Goblet Squat. The Goblet Squat itself is a great gem. Gets back to a clean basic squat pattern. Credit to Dan John for bringing this to the masses.
How to do a Pulsed Goblet Squat:
1) Hold a dumbbell or kettlebell close to your chest. This forces you to keep your chest up. Now, squat down and drive your knees open with your weight on your heels
2) From the bottom position, press the weight out until your arms are fully extended in front of you. You will feel the lower abs kick in big time
3) Bring the weight back in and stand up, driving through your heels and squeezing the glutes together
Congratulations! You just have done a tremendous exercise and are learning to engage the glutes with the lower abs, while providing mobility to the hips. Now, get back to work to achieve that rock-solid core you've been dreaming out!