If you're overweight, there's no way any crunches or ab building exercises will improve your abdominals. You need to lose weight. Eat right, exercise more.
put your armpits over a sturdy bar and lift the knees up to the chest. these are reverse situps and are easier on the lower back.also speed walking in water and swimming are excellent low impact excercises. walk with a walkman playing music or reading a book to you. good luck. start protecting your heart today . this is when trouble starts.when you are young!
Do 3-4 sets of crunches. Do cardio every 2-3 days for about 30-45 minutes (jogging not walking).
In your situation(since youre overweight), the ONLY way you will beable to reveal your abs is to lose weight. When you are at about <10% bodyfat(you can find this out with calipers),then you may start to see your abs. At this point, you may wish to do ab exercises, and these could include situps/crunches/etc. When doing situps, crunches etc, though, remember to breathe. Exhale going up, inhale going down. That way youre working your abdominals to the fullest extent.
Eat right first. Diet is key. With the right diet, fat can be easily shredded with exercise.
Abs come later. If you don't burn off the fat you will never see abs.
Fat doesn't turn into muscle you must lose it first.