If you read my post dated 7-4, I made a clarification. It's not just the L4 itself, it's ALSO THE NERVES THAT BRANCH OFF the L4 that, in my theory, should be examined.
I realize that I should have clarified in my post dated 7-3. I simply used "L4" as a short hand. And I can see why that can be misleading.
There are other nerves that branch off the L4, such as the femoral, that might be worth examining.
And I very much doubt most chiros have the training for the type of testing I'm referring to.
It's a neurologist you should see.
Again - and I emphasize this - mine is just a theory.
To recap that theory, when you use your quad complex (VMO, VL, VI, RF) as agonist (the primary), you get a negative reaction. Perhaps there is/are some type of irritation or impingement along the nerves that branch off the L4.
This may explain why squats, leg presses, leg extension cause a negative reaction (the quad complex are all primary actors in these exercises). These muscles are innervated by nerves that branch off the L4.
You also mention that movements such as kb swings and deads do NOT cause negative reactions. In these movements, the quad complex are not the primary movers. And the hamstring complex are NOT innervated by nerves that branch off the L4. So, even if the quad complex is being activated, perhaps that level of activation is not enough to cause a trigger.
The only unilateral work you mention doing are leg extensions and leg press. Since little to no stabilization is required on these machine-based exercises, I doubt your glute medius and minimus are activated to a sufficient degree. The glute med/min are innervated by branches of the L4.
The glute max is innervated by INFerior gluteal nerve, a branche of L5, S1, S2. The kb swings and deads you do recruit the glute max.
But it's questionable if YOUR EXERCISE SELECTION AND EXECUTION recruit the glute MEDIUS/MINIMUS to a significant degree. In other words, that hypertrophy you've noticed could primarily be at the glute max. The glute med/min are innervated by the SUPerior gluteal nerve, a branch of the L4, L5, S1.
So, again, my theory that you may want to discuss and test for with a qualified neurologist is the following:
1) Your quad-dominant exercises may be creating an issue with the nerves that branch off the L4.
2) This radiates to the nerves that innervate the glute med/min, which also are innervated by branches of L4. Perhaps the femoral to the superior gluteal...???
This could explain that pain in your hip whenever you do quad-dominant activity. Another muscle that is innervated by the branch of the L4 is the tensor fasciae latae. If you look this up, you will see that it's location is also where people refer to as the hip region.
3) The hip extension movements you perform may NOT recruit the quad complex and glute med/min to the degree that they irritate the nerves that branch off the L4. This could explain why kb swings and deads do not cause a negative reaction.
This is why I suggested getting tested for issues with nerves that branch off the L4.
As you can gather, there is a complex network of nerves involved. Furthermore, this theory is certainly not air tight.
However, the one paradigm I do feel comfortable is that you are most likely at a point where you need to start eliminating what the cause is not - AS LONG as it does not make your situation worse.
This is why a neurologist is a better option as they should be able to utilize more sophisticated testing modalities compared to most chiros.