How do the cobra pose work lower trapezius so hard ?

if i understood well, lower traps are responsible of scapular upward rotation and scapular depression.

But why the cobra pose wich is essentially a shoulder extension with thoracic extension give me so musch lower trapezius activation ?! 
To be honest, the activation is so intense i even get lower traps cramps for doing this exercice.

Do you think i can make it my main lower traps exercice in my rehab/ corrective routine  ? (i don't have any particular injury, it is just for shoulder impigement prevention)
 

edit : i just saw it is called locust pose actually

2 hours ago, Victor A MOUCLIER said:

if i understood well, lower traps are responsible of scapular upward rotation and scapular depression.

But why the cobra pose wich is essentially a shoulder extension with thoracic extension give me so musch lower trapezius activation ?! 
To be honest, the activation is so intense i even get lower traps cramps for doing this exercice.

Do you think i can make it my main lower traps exercice in my rehab/ corrective routine  ? (i don't have any particular injury, it is just for shoulder impigement prevention)
 

edit : i just saw it is called locust pose actually

Traps are involved also in the scapular adduction  BUT probably the main contraction that you areperiencing is in the erector spinae.

21 hours ago, Alessandro Mainente said:

Traps are involved also in the scapular adduction  BUT probably the main contraction that you areperiencing is in the erector spinae.

Thanks Alessandro, maybe it is the top part of erectors i guess you are right.