Shoulder shrugs are the most common exercise used to target the upper trapezius area. If you're unsure as to which muscles the upper "traps" are, just picture a really muscular guy with large muscles around his neck. Large traps almost make for a "no neck" appearance.

When you see people performing shoulder shrugs in the gym, it's likely that they're doing the exercise with either a loaded up barbell or the largest dumbbells they're able to hang onto. There's two likely reasons for this. 1) They want to impress the people around them and 2) the traps actually do respond best to heavy weight. However, I'm sure the first reason has more of a influence on why they selected the heavy weights than the second.

The traps have a high distribution of fast twitch muscle fibers. These fibers have a greater potential to generate explosive power than their slow twitch counterparts. Fast twitch fibers also have a greater potential to hypertrophy (enlarge). While heavy loading is ideal when performing shoulder shrugs, you don't want to overestimate yourself and go heavier than you can handle. Technique always comes first and shoulder shrugs are no exception to this.

When performing shoulder shrugs, you want to ensure that you don't allow your head to protrude forward as doing so will place a large amount of stress along the neck region; thus, increasing your risk of sustaining a herniated disk. You'll also notice that with shoulder shrugs, you'll fatigue rather quickly - even when using relatively light weights. This is of course due to the high distribution of fast twitch muscle fibers (they're less suited for endurance).

As for the most effective way to perform shoulder shrugs, I prefer the dumbbell version to the barbell version. However, with that being said, the barbell version has been shown to be highly effective providing you position the barbell behind your body. Performing shoulder shrugs with the barbell positioned to the front of the body is not recommended. You can also increase the effectiveness of shoulder shrugs by drawing the shoulders back a little bit as you elevate.

So what if you're not interested in obtaining big traps? Should you still perform shoulder shrugs? The answer - of course you should! Well developed upper traps (achieved through shoulder shrugs) provide protection to a nerve known as the brachial plexus. The brachial plexus is a series of nerves that runs from the spinal cord, between the vertebrae, into the shoulder and down the arms. A common injury to this nerve is known as a "stinger" or "burner" and occurs when the neck region is forcibly hit to the side.

So there you have it. The benefits of performing shoulder shrugs go well beyond loading up the barbell and looking strong in front of the girls in the free weight area. Shoulder shrugs should always be performed using strict form (as you now know) and will make a great addition into your routine.