IMVHO (correct me if i'm wrong), just do as much ab exercises as u can, with variety. no need to decide which works best,which not. since every exercise has its pros n cons, alternate ur regime with different abs exercise, plus we work out for lifetime not for certain period only, variety will be nice. mixed together all exercises, train consistently, u will see result.

strength training builds muscles, but cardio helps to trim outer subcutaneous fat so those muscles will become visible. if ur fat outside, no matter how developed ur abs are, u cant show them off. ppl keep saying have to be careful doing cardio, so muscle wont be burnt away but for me, if i stimulate their growth evyday, there's no reason to lose them. anyway i'm not really a body builder, what i'm doing rite now seems enough to keep me satisfied.

and of coz the trickiest part one shudnt take for granted - diet.

p/s--- i cn hold plank for 2 mins! :-D if i do it first in morn, with caffeine, cn last till 3 rep but trembling all over la hehehe. gud whole body exercise...

my instructor shouts evytime in the class when doing sits up, observe urself, must open up elbows i.e elbows directed to the side, not up i.e make sure arms are parallel to the floor and imagine there's an apple btw ur chin n chest. this prevents slouching on the floor.

however i see lotsa guys do situps wit elbows directed up, even once a male instructor in class demo this type of situps. i wonder why, and if this shud bring any difference. i direct my elbows to the side tho, coz dats how my idole does hers. :-D

n sumtimes i'm not so sure every weight gain equals muscles, i tend to overeat if i feel overworked, can pack fat as well.
my 2 inexpert cents.

then wats the purpose..bring out sternocleidomastoid muscles? haha.. big neck, no abs

heee. no la. sounds like fitness instructor

anyway i do agree if u do full situps (90degrees) must strengthen back..otherwise, hi risk of disc herniatio due to uneven load when u unintentionally arch ur back in effort to lift ur upper body up. but if do only up to 30-40degrees, enough when scapulas r lifted not touching ground, making sure small back is fixed to the ground the whole time i.e back wont arch, i think it has less risk for back problem. no? correct me if i'm wrong..

fix big mirror la on the wall. easy to exercise..