This is a very interesting discussion. I don't consider myself an expert either yet I would like to make a few comments:
...Since the elbow is so bent, you are propelling the knife forward with half of the leverage available if the arm is at nearly full extension. For me this substantially decreases my range.
… I have a buddy who throws Russian all the time and relies on much heavier muscle that I have to get distant hits with the shoulder and arm still bent.
The elbow is not just "bent" it is also "locked" meaning it acts as a link in a sequential multi-link system: body => arm/elbow =>wirst=>index finger=> knife
No muscle should be involved for the purpose other than locking the arm / elbow - only so called "springy deformations" in your ligaments and tendons (that what a Fedin purist would say, but in practice I find it difficult to achieve)
Here is a very important tip: the elbow bone should always be pointing down towards the floor and always positioned in front of your hand / wrist.
In Fedin's system It is ALWAYS a pulling motion, NEVER pushing.
If you find your range decreases you are likely pushing the knife (i.e. your wrist got ahead of your elbow) and you have probably engaged the muscles.
The "Russian" throws take more release control (lots of practice) to guarantee a point-on stick if one is throwing more than 10 feet or so.
Actually, this is an interesting one. The phenomenal thing about Fedin's style is that after the magic 10 feet limit you should not make any adjustments at all unless you are using a different knife.
It has been illustrated (and can be seen in some slow motion videos) that when the knife first exits the hand it slowly turns in the air and after flying aprox. 10 feet it stops turning and begins to fly almost horizontally for the next 10-15 feet. So all other things are being equal you should make no adjustments at all and throw exactly the same way you do from 10 feet. Now, this is where I struggle too. My eyes and my mind simply refuse to believe this is being the case and I tend to make some adjustments where I should leave it alone. Now some folks on Russian forums recommend to overcome this by throwing with your eyes closed, imagining you are throwing at a glass wall just 10 feet away, etc. just to trick our natural propensity to adjust. This is kind of hard even though I have little problem doing this from about 15 feet now, but the further I get from the target the more I engage the muscle and the closer I am getting to the Thorn style. Also, this results in less powerful throws.
Fedin style seems to me to be a sort of hybrid of Thorn style and shuriken style, where the release is more of a frozen wrist, with early release (which creates the more elongated quarter spin flight pattern). Power is generated by an elongated wave motion of the whole body, which makes for a slow release where Thorn style has a much quicker and compact release.
Ralph, thanks for your thoughts, but I would respectfully disagree on the wrist issue. In Fedin style the wrist is never frozen except when it is locked at the end of the first wave (assuming the vertical plane of throw the palm towards the ceiling and the index finger with the knife tip pointing away from the target).
Re: the index finger: it acts as the last link in the chain (some would say that it is the knife which is the last one) with the knife inertia forces applying on it a downward pressure on the finger. When the index finger is completely "charged" i.e. it is ready to spring back (this is an important moment that you should wait for before you start the sequential PULL:
a) Pull by turning your body first
b) This in turn will start pulling your shoulder /hand/wrist/finger/knife (all locked acting as a one link)
c) When the motion is in progress (not completed yet) continue pulling with your elbow (by now the knife is springing up on your index finger)
d) Keep the elbow bone down and in front of your wrist
e) Finish the motion with your wrist (release the grip of the handle when the knife approaches your ear) and allow the knife to slide on your index finger
So in reality past 12 feet Thorn style throwers are hybridizing into a more shuriken or Fedin style …
Funny you say that. I thought I was approximating Thorn style when I am past 12 feet

lol...