Shrugs are a great option to build the upper traps, but the traps actually run from the cervical spine all the way down to the lower thoracic vertebrae. They also insert on the clavicle, acromion, and scapula. Your traps are everywhere!
To really build the traps from top to bottom, you need a variety of movements that hit each area of the traps effectively. Farmers walks always makes the list of anyone who chimes in on yoke building.
To create tension in the musculature of the back, set the scapulas into retraction and depression, i.e. put your shoulders into your back pockets and get the chest out. You should feel this in the mid-traps and rhomboids if you're doing it correctly.
You should also have the lats flexed and maintain a neutral spine. When you throw all of these things together, the farmer's walk does an awesome job of growing the yoke and improves movement patterning for the scap and T-spine.
Remember the following, arranged by level of importance:
- Shoulders back and down
- Chest out
- Lats flexed
- Neutral spine
See where loading is? It's last. If all of the other things can't be maintained, then you're going too heavy!
Do them at the end of a back or leg session for 4 trips of 30-40 yards, using an appropriate load where you can maintain the above position. That means not trying to convince the Globo Gym that you're preparing for World's Strongest Ego.