Cardio Cardio Cardio Cardio

[Quija]

http://www.exrx.net/WeightTraining/Myths.html

It appears we have conflicting sources. Logically though I still don't see how if after a workout your bicep has the burn how you can conclude you did not work it out. Same goes for the abdomen. If the entire muscle worked at once then there would be no need for anything other than a situp or a crunch in order to strengthen it? Or if a movement did utilize the entire muscle(and this sounds like a logical explanation that accepts both the myth and multiple ab training techniques) maybe it gets it's shape depending on the angles you work it from, creating a need for plancks, crunches, situps, leg lifts and all those other crazy ab movements.

Btw for my hanging leg lifts I hold a 10 pound medicine ball between my knees and raise it as high as possible, I do not straighten my legs at a 90 degree angle, maybe it works because I'm focusing on my abdomen and making an effort to raise it that way, or maybe it's just natural, but I have no doubt that it does work.

[TheRuss]

Logically though I still don't see how if after a workout your bicep has the burn how you can conclude you did not work it out.

There are multiple muscles in the same region. From the section FC quoted:

The Iliopsoas, particularly the Psoas portion, happens to lie deep below the lower portion of the Rectus Abdominous.

Meaning that this is what's happening:
-You perform a certain exercise (the hanging leg lifts, if I recall correctly)
-You feel the burn in a certain region of your body (your front lower abdomen)
-You look at an anatomic image (like the one in this post) and see a muscle that overlaps with the area of the burn
-You assume that the burn is in the overlapping portion of the muscle in question, and thus the exercise works that portion of the muscle

The problem with this reasoning is in the third step - namely, the rectus abdominus overlaps with the iliopsoas, which is the muscle that's actually "burning".

Same goes for the abdomen. If the entire muscle worked at once then there would be no need for anything other than a situp or a crunch in order to strengthen it?

The abdomen is not a muscle, it is an anatomical region. There are a lot of muscles in that region, and correspondingly, there are a lot of exercises to train them.

[Fighting Cephalopod]

http://www.exercisexpress.com/muscleormyth.htm

[TheRuss]

Addendum: Lockridge's statement depends on the fact that the muscle fibers of the rectus abdominus run uninterrupted from the ribcage to the pelvis. What confused me initially was the presence of the tendinous intersections - all the diagrams I'd seen implied that these intersections ended one muscle fiber and started another. This appears to not be the case:

The anterior layer of the rectus sheath is firmly attached to the rectus muscle at three or more tendinous intersections. When this muscle is tensed in muscular persons, each stretch of muscle between the tendinous intersections is indicated by grooves in the skin between the muscle bulges.

- http://download.videohelp.com/vitualis/med/abdomen.htm