TRAP TRAINING WHAT DO THE TRAPS DO AND HOW TO TRAIN THEM
Training the traps has been mainly done by performing shrugs which is not the most effective trap exercise since the traps are not strong elevators of the scapula but rather upward rotators of it and the clavicle. Because of their diagonal line of pull the traps upper and middle traps perform retraction rather than strict elevation (Johnson et al 1994). You can see the difference by palpating your upper trap and performing elevation strictly up and then raise your arm which will perform upward rotation; you will notice the difference in how much the trap is contracting.
To train the traps it may help to perform retraction based exercises that focus on drawing in the shoulder blades together rather than elevating them. This can be done with scapular retraction, full rows, face pulls or wide grip shrugs which help facilitate retraction and upward rotation. The wide grip shrugs have been shown to lead to greater trap activation (Pizzari et al 2014). A good way to train the traps for strength however is farmer carries which helps build strong isometric strength which can be helpful for strength training lifts like the deadlift, and Olympic weightlifting.