[quote]Professor X wrote:
buffalokilla wrote:
Tell me, how do people develop an imbalance between their VM (specifically the VMO) and their VL? It’s all quads performing knee flexion, isn’t it?
http://www.biofitness.com/anatomy.gif
The heads/bellies of the quadriceps:
Heads
- Rectus Femoris
- Vastus Lateralis (Externus)
- Vastus Intermedius
- Vastus Medialis (Internus)
From another site:
The biarticulate rectus femoris [1 ] enters passive insufficiency through the completion of knee flexion when the hips are more extended or through the completion of hip extension when the knees are more flexed. The biarticulate rectus femoris [1 ] enters active insufficiency through the completion of knee extension when the hips are more flexed (other heads of the quadriceps [2, 3, 4 ] become more active) or through the completion of hip flexion when the knees are more extended (other hip flexors become more active).
[/quote]
This has no bearing on what I asked…
it just explains that the rectus femoris doesn’t contribute much to knee extension when the hip is flexed, much like how seated calf raises “target” the soleus. Or how it can’t contract any more to contribute to hip flexion when it extends the knee while the hip is flexed. The rectus femoris rarely contributes to patellar tracking issues outside of being too tight.
Those are two of the most ineffective exercises for correcting a VM/VMO imbalance around. Pederson stepups, sled dragging, and full front squats performed with forward knee motion work much better.
It also doesn’t describe the pathology.
But anyway, you missed my point, I was being a little sarcastic. I was trying to get you to think about the physics involved in muscle action. Without drawing a huge force vector diagram, the VL produces more force than the VM when you’re performing motions involving abduction and knee extension, such as parallel powerlifting style squats. Each of the 4 quads is innervated seperately, and many different bundles of fibers within each of these 4 seperate quads are innervated seperately; they just usually are all activated at once to perform a task that demands it.
My point here is that if someone has been doing situps/crunches improperly so that the right or left side of the rectus abdominus has been doing more work than the other (due to any number of things, including tightness on one side of the lower back, hip flexor dysfunction, a bad habit from being uncoordinated, etc) you CAN develop unevenly. Saying that because the rectus ab is one muscle it must all develop evenly is ignoring basic physics. By your description, I could load a 50lbs weight to my right shoulder and do normal crunches for 20 years and not have the slightest bit of unevenness in my rectus ab.
It’s not really pertinent to this discussion though if the original poster doesn’t have any dysfunction, though this picture you speak of doesn’t seem to exist (at least any more). Couldn’t find it by going to his profile and looking at all of his posts.
As always, consult your physician before believing anything anyone on here says, as we’re not doctors (well, most of us anyway).
-Dan