Let's have some informative opinions please.

What does the standard say about loin?

What is best length of loin for a GSD?

What are the good and bad about long and short loins.

What I know

Longer loin is good for galloping dogs

Longer loin is good for taking sharp turns

shorter loin means a stronger back

Shorter loin provides more space for chest and thus more space for organs

What are your thoughts ?!

thoughts, you asked - the key is looking at the whole dog and how all the bits fit together in harmony.

reductionist science is not a virtue in this case.

longer/shorter than what???

longer than a short loin and shorter than a long loin???

to have a productive conversation i think you need to state ratios of one complimentary component over another, i don't get long/er, short/er.

then of course the ratios only have meaning within a whole context of purpose and function, a street fighter only needs enough loin to facilitate lateral flexibilty.

just my uneducated opion, take it for what you paid for it.

Well when I read a critique I sometimes see "long loin", "slightly long loin", "short loin", "slightly short loin". I do not see a specific loin length stated in the standard like 15 cm for example. My conception is length of loin is relative to total topline length (i.e neck+ withers+ back+ loin+ croup).

I believe we recognize a long from short loin by looking at a topline, hence the comments on the shortness or extra length of loin. But what is the acceptable length or length ratio to the back, is there one?

What is good about long loin and what is not?

What is good about short loin and what is not?

Some divide the total dog back into 4 parts, withers, back, loin and croup. We know the longer the withers the better, we also know the longer the croup the better. Is it correct to assume the shorter the loin the better for a trotter? how much short or shorter say compared to total back length? Just wondering.

Is a short, shorter loin healthy for a female GSD? is a loin that is considered slightly long for a male okay for a female?

Ibrahim asked

What is good about long loin and what is not?
What is good about short loin and what is not?

Most of the old American books state the loin is to be short because they want the maximum length of the dog to be composed of croup length and thoratic length, these being areas where the bulk of leg musculature attaches on vertibrae/pelvis/ribcage. It is said females can be allowed more loin length as it would give room for a litter. The reasoning is if these areas are larger they give the ability for larger limb muscle developement. I've never seen a critique say "croup too long" or "loin to short" that I can remember.

If you can stomach it, as it is a little graphic, you can watch videos on canine anatomy that will show the actual muscles and how they are attached. Some are from actual dogs, other plasticized dogs or from computer generated graphics.
3D Canine Anatomy Software 1.1

Veterinary, anatomy, dog, muscles