range of movement

[Cantabrigian]

You're obviously not going to be able to play tennis with a tailored jacket on but how much of a range of movement should there ideally be?

During the What is Drape discussion, Manton mentioned his performance tests for a jacket:

Fred Astaire famously used to test his A&S commissions by pirouetting around 32 Savile Row and stopping in improbable poses to see if clothes were laying correctly on his body.

I have my own, less poetic test. First is the "cab test". Can I raise to extend my arm to hail a cab easily? Does the collar lift from the neck when I do? Do I feel the coat pull across the back? Second is the "steak test." I sit down and mimic the action of eating: cutting, reaching for a glass, etc. Same principle applies. This also basically covers normal, everyday activity such as writing and using the phone. Finally, the car test. Can I manipulate the wheel easily? Shift, etc.?

I have found that a lot of coats that look good when you are standing, arms down, pass few or none of these tests.

and Concordia added

Can one tie a pair of shoes without wrenching the jacket apart?

I think this photo from tiger02 illustrates a jacket that moves very well:


What specifically contributes to that sort of freedom of movement?

high armhole? extended shoulder? fullness in the back (from either the shoulder or back seam)?

Why is it such a hard thing to achieve?

[Concordia]

Beats me, but when a tailor delivers it, I give him repeat business.

[yachtie]

I have to be able to sit at my desk and do my work with the jacket on and buttoned without hindrance. Aerobic flailing a la Astaire is more than I need and would necessitate a looser coat than I like.

[Concordia]

Looser or tighter? I find that the jackets that generate the greatest illusion of slimming on my physique are also those that provide the most freedom of movement. YMMV.

[yachtie]

I've found that too. If it follows my body, there is no hindrance. I'm thinking more of the A&S look which has extra material under the arms. I own none, but it appears that it'd be more suited to jumping around.

[Concordia]

More material from the armpits up, very tight armholes, and a certain amount of hugging the torso from the armpits down.

[Martin Stall]

Both of you are right IMHO. The smaller the armhole, the less the sleeve will tend to lift up the body of the coat when moving one's arms. As you can see in the picture this is why the collar and the shoulders stay nicely snug on the body. Sometimes people are seen on tv, sitting at a table or desk and the shoulders float somewhere at the level of the ears. Low armholes.
Also excess drape can cause bad behaviour. There should be some drape behind the arm though.
Another thing is the shape of the top part of the coat. Finally, a badly cut sleeve will look and feel horrible.