Rick wrote:
The extended arm exposes one of the weakest joints in the body to a lot of
risk and, worse, is a weaker position for controlling the boat. Yes, it will
work (until the forces on the lever exceed the abilty of the joint to bear
the stresses), but will it work better than a brace done with the elbow
tucked into the top of the hip and the power side of the blade on the wave?
The answer to that is absolutely not.

Once the wrists go above the head, the shoulder joint actually loses both
strength and flexibility. You can test this while sitting in your chair.
Extend your arms fully over your head and try to slide your wrists to either
side (without twisting the torso). It is almost impossible to move more that
a few inches in this position. Put the wrists at shoulder height and do the
same motion and, voila, your range of motion has increased considerably,
from a few inches to a few feet. More importantly, the muscles have
considerably more mechanical advantage from this position, so not only is
the shoulder protected, you actually have more available power to apply to
the paddle. Note that most of the side-to-side motion available to the
shoulder joint disappears when the elbows go above the shoulder. Both
flexibility and power are lost as the elbows move closer to a locked
position above the shoulders.

The problem with this is that it's very limiting (I'm talking sea kayak
use here). It's useless on beam waves much above head height unless
bongo-sliding out of control is your idea of a good time in big waves
(sure, sometimes it's a blast, but not on rocky coast or in areas where
the waves are dumping). What I prefer to do if I want to maintain my
position is to reach up, pierce the wave face with the paddle and dig it
into the back side of the wave. I let the boat flow with the wave and I
end up essentially horizontal as the wave crest passes under the boat.
Once the wave releases the boat, it only takes a quick snap to be
upright again. Although my arms are extended during this maneuver, there
is very little stress on them or my shoulders and what there is in
inline with my torso.

This is about as far from the ACA/BCU high brace technique as one can
get and I don't claim that it's safe, but it's saved my ass from getting
slammed into rocks a couple of times.