When you do the shrug exercise you should not let the shoulders or the head move or roll forward. If you do let the head and shoulders roll or move forward, there is an excessive compression, torsion and sheer placed on the acromioclavicular and sternoclavicular joint. Over time, this can cause damage and painful degeneration. One such example is clavicular osteolysis. (to paraphrase Paul Chek)
When you do the shrug correctly, the weight is equally distributed throughout the entire rib cage, shoulder girdle and head neck complex.
Where do you see poor form most often? With dumbbell shrugs to the front. Instead of the proper position of retracted shoulders placing the load evenly, the person will hunch forward protracting the shoulders and craning the neck causing all the above mentioned “nastys”.
What happens if you shrug incorrectly? You can get a stinging, tingling, numbing sensation from compression of the brachial complex that can migrate down your neck to your arm and into your fingers.