Today I do hanging knee raises where I crunch my knees pass parallel to the floor. I do 2 sets totaling about 80 reps.
Tomorrow I will use my weights and probably do deadlifts and squats. I do 2 sets of each with those too.
I got to do it more often. I try to workout 4 times a week but that doesn't always happen. I'll be 73 this week so I'm slowing down a bit.