Why is "back extension" exercise called "back extension"?
Let's consider the following picture taken from here:
Well, in this picture I cannot appreciate any back extension. What I see is a perfectly neutral back in both the starting and ending position. I don't see any lumbar and back extension and flexion during the exercise. What I see is simply a glutes exercise: glutes long, glutes short.
And I think this makes sense, since an arched or flexed back could apply an excessive force to the spinal disk since this exercise may be also performed with a load, as shown in the picture.
So, where is the "back extension" in this exercise? It seems to me a pure glutes exercise.
For instance, I see very well the back extension and flexion in cat cow exercise.