DZ said:Steve Freides said:DZ said:Steve Freides <[email hidden]> wrote:
> DZ, I will look at that thread later, but please post an exrx.net
> link to
> the press you're doing.
Sure you know what the shoulder press is. Anyway, I'm doing these -
http://www.exrx.net/WeightExercises/DeltoidAnterior/DBShoulderPress.html
http://www.exrx.net/WeightExercises/DeltoidAnterior/BBMilitaryPress.html
but not this one -
http://www.exrx.net/WeightExercises/DeltoidAnterior/DBArnoldPress.html
The AP is sufficiently close to them so why bother if there'd be a
higher risk.
If full ROM and strength throughout a full ROM is your goal - it is
mine - then what is the higher risk of the AP?
I don't understand this sentence :-) How having certain goals could
alleviate the risks? Perhaps the risks are largely alleged and
theoretical. Your point seems to be that there is a large kettlebell
community that routinely practice something resembling AP without any
problems. So there are millions of people who smoke and all the
evidence there is epidemiological only. Maybe JMW and others could
write some more on the rotation problem in AP to help us out...
OK. I'll respond because you asked, not because it will convince
Steve. Given the basis of his convictions, nothing will.
Let's take a pictoral look at one the classic forms of rotator cuff
impingement: impingement of the suprspinatus muscle within the
subacromial space, i.e., the gap between the acromion and the humerus.
Here is an image of that area:
http://www.healthopedia.com/bursitis/bursitis.html
That image shows inflammation of the subacromial bursa, but
eventually, the impingement will affect supraspinatus tendon, too.
See how that tendon must slide back and forth in that little space
between two bones?
But wait, there's more! That space is not constant; it increases and
decreases, depending on the position of the upper arm. And the
position of the upper arm has at least two aspects: [1] rotation and
[2] adduction/abduction. So what happens with that limited space as
the upper arms are raised (abducted) and rotated medially (internal
rotation) during the process of the Arnold Press?
Well, I could do the classic Lyle-style educated speculation, but
there's no reason to do that when there have been actual radiological
studies of that movement:
Graichen H, Bonel H, Stammberger T, Englmeier KH, Reiser M, Eckstein
F. Subacromial space width changes during abduction and rotation--a
3-D MR imaging study. Surg Radiol Anat. 1999;21(1):59-64.
http://tinyurl.com/sxdzv
That study found:
"During abduction (from 60° to 120° of abduction), the minimal
acromio-humeral distance was found to decrease significantly. This
reduction is at least partly caused by the greater tuberosity [that
big round portion at the top end of the humerus], which approximates
to the acromion between 60° and 120° of abduction. However, this does
not necessarily indicate that the supraspinatus tendon is mechanically
irritated in these positions." p.
OK. That means that the space gets smaller as you raise your arms,
but the supraspinatus tendon doesn't necessarily get squeezed because
that also depends on rotation. And the degree of internal rotation is
the difference between a standard dumbbell military press and the
Arnold Press, with the latter having significantly more internal
rotation.
What happens when you add internal rotation? Well, at 90° abduction,
"[d]uring internal rotation the minimal distance passed through the
supraspinatus tendon in all cases and reached the acromion at its
anterior inferior border. *** In external rotation, on the other hand,
the vector was located at the central part of the acromion and passed
through the supraspinatus tendon in only 5 of the 12 volunteers."
So, at 90° abduction with internal rotation, everybody gets their
supraspinatus tendon squeezed in the subacromial space, while less
than half them get squeezed with external rotation. And if you look
at the Arnold Press movement, you get 90° abduction with internal
rotation about 1/2 - 2/3 of the way through the movement. So,
basically, the conclusion was:
"At 90° with internal rotation, however, the minimal acromio-humeral
distance vector penetrates the supraspinatus tendon at its most
vulnerable part and reaches the acromion at its anterior inferior
border." That means max squeezage, dude. Right in the middle of your
Arnold Press.
HTH