The site recommends crunches and leg extensions... crunches are not a great exercise for functional ab muscles, and leg extensions are generally verboten due to stress on the knees from the open chain loading. It's good to be thinking of this stuff though. I highly recommend Athlean-X(his free youtube videos, can't say anything about his programs) and Mark Rippetoe's Starting Strength program. Between these two, I've…
Athlean-X is terrific. He is a highly accomplished physiotherapist and his videos are a treasure trove of solutions to very specific problems. I have been following his video advice on fixing anterior pelvic tilt and lower back pain (a far too familiar problem for our types) and I can feel a tangible improvement on both fronts. As for alternatives to crunches, variations of planks building into hanging leg raises are…
Might be life changing for you. It was for me.