[Ohhkay8]

Are either effective? Which muscles do each of these two exercises work? Is 'more better', or should there be some kind of limit on how many to do during each workout?

As you can probably tell, exercise is pretty new to me and I'm trying to gather all of the information I can maximize the effects of my workouts. I'll probably be asking a lot of questions, hope that doesn't bother anyone! TIA.

[northernbelle]

Crunches work mainly your upper abs, with your back being the stabilizer. Situps work all the way to your hips, because they have to pull you up to a sitting position.

Effectiveness: that depends on your goals. There are many exercises to work your abs, and to work your back. I would mix them up. That way, you don't adapt to any one exercise.

Repetitions: I personally feel more than 15 reps at a time is not efficient. To add intensity, you could hold a dumbbell or a weight plate to your chest.

Don't worry about asking questions. Everyone has to start somewhere, and you don't get anywhere unless you ask.

[Blueyedblond]

Crunches work upper abs like Belle said - you can modify them to target other areas though - there are side crunches for the obliques and reverse crunches for the lower abs - and for some people- regular sit-ups are hard on the back

[stef]

Sit-ups: those things sporty people do - from lying down to a full sitting position! Often done with the feet trapped. Can be done with VERY little effort, because trapping the feet gives you something to pull on and the LEGS do most of the work.

They also tend to get done very quickly - so your body weight gets the work done, as you bounce up and down using gravity and that 'bounce' off the floor to get the move completed.

Crunches: work by moving the heaviest part of the body (your head and torso) through a small(er) range of movement, using an isolated groups of muscles.

I won't go into the science - cos people like to talk about 'upper' and 'lower' abs - cos that's what you FEEL as you do crunches, rather than the way the muscles themselves work (sorry, I am a sports lecturer and am winding myself up for a return to College) BUT by moving more slowly you recruit more muscle fibres and more muscle groups to complete the work. By adding a twisting movement you can increase the usege of the deeper abdominal muscles (internal and external obliques - or the outside edges of that six pack thing) and by adding more control and postural alignment you can add the deepest muscles around the pelvic girdle - the transversus - for increased stability and support.

For sports or activity specific fitness the sit ups can be very effective.

For fitness and strengthening of the core then crunches are most effective - and less likely to cause injury.

As for technique, Active.com has a good written answer, that neither the sports scientist or instructor in me would disagree with

http://www.active.com/story.cfm?stor...egory=keep_fit

And this guy is quite sweet, he may stumble over his description and move a bit fast but his technique for a basics crunch is good

http://www.youtube.com/watch?v=6HxSeY-XXHc

Do the basics first then add in the twists or some resistance (more later if you like) but start off slowly and build up your work load - you have to work out what you CAN do before you add weights or other difficulties!

It is often quite confusing to start exercise - but lots of people on here have lots of different viewpoints and experince of it - so you are bound to find someone who can explain what you need - just keep on asking