Lower abs and such

Lower abs aren't fair!
I used to do bazillions of Crunches, and Twisting Crunches until the cows came home and asked why I looked so silly, but with no visible results.
Oh heck.
I understand that the abs are There, but are not visible without paring down so that they show.
Anybody have a magic formula for achieving fairly good abs, upper, lower, or whatever...?

Has anyone had success with "Jack Knives" as an ab exercise ?
Feet on the bench, hands on the floor, body in flat position. Then knees pulled up as far as practical, and slowly returned. Repeat until tiny drops of blood appear on your forehead...?

First off abs are much more 'diet' than training - if you've lifted heavy (with squats, deadlifts, standing shoulder press etc) then you'll more than likely have abs without too much extra training (not to say extra training is bad, or won't improve things more, but there will be some ab development as a main goal of the abs is stabilisation). Be honest with yourself about your fat levels covering the lower abs. For a high % of males the lower abs are the problem area (like for most women it's thighs & bum), the problem is it's the first to gain fat & the last to lose fat, so many guys have to get to a pretty low bodyfat% before the lower abs show through. Also the older you get the harder these regions get to lose the fat. I'm a lower abs fat holder myself, so it just about every guy I know. I know maybe 2 out of all the athletes I know who have got decent lower abs year round, both are pretty young guys. I'm not saying it's impossible to get, just it demands a bit of commitment to hit those fat levels for some (& yes for a few they can't do it unless they get down to unhealthy fat levels).
The exercises are more controversial at the moment. A few years ago a top back expert (Stuart McGill) wrote a book arguing that all flexion exercises for for the abs actually damaged the back. He used the analogy of flexing a credit card...you can bend it once, no issues, twice, again no issues, but keep bending & bending & eventually you'll get a bend mark in the card , keep going & you'll split the card in 2. These days a reasonable number of coaches have dropped most, if not all of their flexion movements for the abs & relied solely on rotation, anti-rotation, stabilisation movements. I do have a few issues with this. One being back design - it 'looks' like a design specifically meant for flexion, if you were just supposed to stabilise you'd have a solid bone, not a load of vertebrae (in my view anyway). But I do believe that the stability work for the abs has been neglected in the past in favour of the 'crunch' type moves.
If you have any back issues that do not do flexion moves at all. I've got a bit I did on the VBB blog here - if you've not done any stability work before then start by including these. once you've got them down I'd work on one leg/one arm, (bird dog type variations), then you can add movement if you like. I'd also include some rotational work like using a tornado ball, Russian Twists etc.
My main focus would be on my diet. You'll almost certainly have to diet down to get those abs showing at the bottom.
I haven't tried that exact variation of the jack knife, I have done 'v-ups' with your body out straight on the floor, keeping the legs straight, bring your legs & body up to meet each other. For any flexion move I think it might be best (just incase the experts are right) to do less reps & create harder variations, or try out something like a Barbell rollout which is like an ultra-hard plank style variation. It's like those little wheels you roll out on , but with a barbell you add weight & so are pulling a weighted bar towards yourself -the more weight on the bar the harder it gets to pull it back up.
So, basically:

1/ Diet
2/ Vary your training, so you do less flexion & more stability, rotation work
3/ Don't drop flexion, but work on less reps with harder variations
4/ No need to train abs daily, just train them very hard a couple of times a week (not long, just hard)

That would be my suggestion for you to try out

Yes, abs have become a touch stone of fitness, and it ain't that easy. Sit ups and twisting situps are okay, but they won't do the job. Neither do the hanging leg raises I do.
Maybe nothing really will...

"...many guys have to get to a pretty low bodyfat% before the lower abs show through. Also the older you get the harder these regions get to lose the fat. I'm a lower abs fat holder myself, so it just about every guy I know..." --Pete

True. Blowing out candles on the birthday cake puts on weight... and changes the metabolism too. The women I know--lovely as they are-- complain about this, and men lie about it.
But it's still worth the try. Even if I never get to have washboard, six-pack abs I still look and feel better about the results if I try.

Gotta remember, working out isn't easy, but it's easier if you're having fun doing it.

"Russian Twists,"
Okay...I like Russions...
...Probably because I am related by... to them...

I have an extra bar and few spare weight plates in the gym ;and can rig up a nother corner with bar-butts than won't chew into the cherry floor of my home gym.
I'll let you know how I'm doing...

I actually got a little device like this. If you're worried about floors you can do Russian twists, you can also do T-bar rows. You can just attach it to your bench, rack or other solid base & off you go. I've also got a straight handle so I can do wider grip t-bar rows. You can also use either Olympic or standard bars on the one I've got, finally you can also use it as a lock & load substitute if you get the urge to do arm wrestling practice

I personally think those "bullworkers" or "Iso 7x", those things are good for the abs, lower abs but should not constitute a major part of one's exercise regimen.

By the way, Sandow I read made a multi-day fast, maybe over 10 days even to show his definition in a photo shoot so talking about BF, Body Fat and all that makes sense.

I know of this one guy who ate nothing but tuna to get into in season condition from his off season weight.

I'm not saying I need serious fasting but a little bit, maybe a day here and there might be good for my system.

If you want the last info on intermittent fasting then you might be interested in 'Eat Stop Eat'. I think ideas like this work for some people, it depends how you're put together, some people can go 24hrs not eating without issue, while for others it can be a counter productive strategy. It another one of those 'suck it & see' types things where you have to try it, to see how you'd fare. I'd probably keep a food diary & write down what I ate on the lead-up, what I ate afterwards, how I felt during, how it affected mood etc.
For some a daily lowering of calories work best, for others maybe an intermittent fast could be best? I tend to recommend a general lowing of calories (with strategic refeeds) as it develops a habit of eating more healthily - which most people who need to lose fat don't do anyway. But certainly there are many ways to take fat loss.