Abdominal crunches and its effectiveness?

Hi all. Just wondering from a physical therapist's point of view on ab crunches. I've heard some physios actually saying that doing crunches with both lower limbs extended are a better form of cunch contrary to belief that it has a chance of causing lower back pain??
Back pain and its risk aside, is it actually a more advance level of exercise compared to the regular crunches with both knees bent? Or does it produce the same results?
I've tried it out and admittedly, with both knees extended, it is more difficult and I can feel the lower abs worked on more. Is this true or more of a psychological effect? Or some compensatory muscle work here causing me to think that way?

One more question, oblique crunches and the best way to do them? According to most fitness guides, the popular oblique crunch is to twist your body to the opposite side of the other knee. However, does this really isolate the obliques? Won't the rectus abdominis contract 1st, thus focusing mainly there and not the obliques? And do you actually need to go up and nearly touch the knee or just a slight twist is enough? Have been trying to find out the most effective way for doing oblique crunches but need some feedback here.

All in all, I do understand that our abs work as one unit and it's difficult to truly isolate just one part. So my final question is, are all these isolation abs exercises (ab crunch, oblique crunch, reverse crunch (for lower abs)) truly effective? Or should one just stick to a simple regular crunch to work out the whole abdominals?? Of couse the goal in mind is not to create a bodybuilder or an athlete, but to at least firm up the abs in the whole. Have been thinking about this as most fitness guides have been creating various abs exercises to isolate the lower abs from the upper abs, but are these really necessary?

Thanks fellow physios ;)

Do crunches work the abs? Answer: Yes. Do they work them in a function way? Answer: No

You need to look at the position of the body when doing a crunch. If you rotate it 90 degrees you'd be sitting and slumping into you waist! The abs are used in an erect position and support the body moving mainly from a standing type alignment into extension (e.g. Throwing, tennis, placing some on a shelf) and rotation (e.g. javelin, tennis, throwing) and often as you can see in a combination of extension and rotation (eccentric strength) and then from that position into 'relative' flexion and rotation (concentric strength).

In addition they are mainly stabilizers, not prime movers like the quads or biceps/triceps. So don't train them in the same way as biceps and triceps as that is again not-functional for what they do.

The crunch exercise would be like doing bicep curls in the last 10 degree of elbow flexion (bend). Basically a waste of time. Try doing the same thing lying over a gymball with the legs/knees extended, that will get you going.

Thanks for sharing information about abs exercise. Many people like to do abs exercise to get 6 pack. Your information will be useful to people who like to do abs exercise. One of my friend suggested mereal6packabs website. In real6packs site, they are telling easy way to do abs exercise.

Mike Ethan

Check out this article by Mike Boyle... top US coach. He mentions Dr. Stuart McGills research that shows that repeated flexion (in a lab setting) can lead to disk damage and is in no way functional. He explains how to train the anterior core (which includes abs) properly. All of his articles are well worth checking out if you are into sports performance, rehab, or training of any kind
TMUSCLE.com | Anterior Core Training=

I found this thread while searching for info re abs crunches & lower back pain. I’m not sure if it’s answered that, but it has raised some other interesting questions (mostly in response to physiobob’s post):

1. I thought the reason that it’s been recommended to do crunches with both the hips & the knees flexed at 90deg while lying on your back was to avoid using the psoas instead of the abs, which could lead to hyperlordosis, so I’m a bit puzzled by your suggestion of doing crunches over an exercise ball with legs extended.
   
2. You say crunches are like sitting & slumping into your waist, but crunches work against gravity whereas slumping is passive – or have I misunderstood what you meant?
   
3. I know crunches aren’t particularly functional, but don’t we use the abs in this way when going from lying to sitting and won’t toning the abs like this enable them to work better when used functionally?

Any clarification on any of these points welcomed!


The issue I originally wanted help with was:

I do oblique crunches most mornings lying on my back with both my hips & knees flexed at 90deg & my calves/feet resting on my sofa. I find this works the abs quite well, but often find that the mid/lower part of my back begins to ache well before my abs. It doesn’t feel like the sort of ache caused by working a muscle hard, it feels more like there’s something not right & that I might be causing myself problems. I’ve tried statically contracting my abs (as in core stability exercises) before starting the crunches & it seems to help, but not all the time.

Any advice/comments, anyone?

TIA, Jeff

Immortal25,
your post was filled with meaningful questions, though all of them rhetorical. Seems to me you are looking for confirmation of your own thoughts and ideas , well ,fine, I agree with you.
Crunches are a fine way to increase core strength, safe, relatively easy and simple to learn. Done with hips and knees bent , will reliably improve the holding power of the front of your back,( so to speak ). The real trouble lies not with wether this or that exercise is better or not ( a bit like polishing apples, they don't taste any better no matter how shiny ), but with the more difficult area of compliance.
Ergo, K.I.S.S. works better than any length to which the energetic exercise zealot could go to achieve better or similar results. The more difficult the exercise , the less it will be done.

Physio aside, those that want to build large abdominal muscles (i.e. a six pack) try resistant training for abdominals.

Rope pull downs allow you to adjust the weight so you can crank out 8-12 reps of intense abdominal exercise.

Weighted leg ups using a dumbell are also good, especially for targeting the lower abs.

You wouldn't do 100 reps to work your chest muscles, so don't do it for abdominals either.

Chris

Quote:

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Originally Posted by JeffK

1. I thought the reason that it’s been recommended to do crunches with both the hips & the knees flexed at 90deg while lying on your back was to avoid using the psoas instead of the abs, which could lead to hyperlordosis, so I’m a bit puzzled by your suggestion of doing crunches over an exercise ball with legs extended.
   
2. You say crunches are like sitting & slumping into your waist, but crunches work against gravity whereas slumping is passive – or have I misunderstood what you meant?
   
3. I know crunches aren’t particularly functional, but don’t we use the abs in this way when going from lying to sitting and won’t toning the abs like this enable them to work better when used functionally?

Any clarification on any of these points welcomed!

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You have good points there which was in my mind as well and therefore I welcome this discussion in this thread. Perhaps some brainstorming would be good for all of us fellow physios and what-not.

Ginger, you're righ, they are my own thoughts as I've been trying to find out how to isolate and work out the muscles in the most efficient way possible. Unlike the other muscles in the limbs which can be isolated easily and worked on, the abs are a tough bunch which I'm so interested to experiment on.