In this section we’ll take a closer look at the back, the muscles that make it up, and the exercises one can do to develop each and every one of these muscles to the best possible extent. The importance, a well developed, thick, and in the same time good quality back has on competition level, probably needs no further iteration. The muscles of the back largely define the overall strength of an individual, the amount of weight one can lift is highly dependant on a well developed back as well. There are three things bodybuilders should aim to achieve in regards to the back: first of all thickness and overall bulk. (without this, the back can’t achieve the required width either), the width and sweep of the latissimus dorsi, and the definition of the muscles of the lower back - the spinal erectors.
But we’re already getting ahead of ourselves here. Let’s just take it slow and try not to miss anything important. Let us first see the major muscle-groups that together make up the back. The lattissimus dorsi (or lats) are probably the most spectacular and in the same time best noticeable not only of the muscles of the back but of the whole physique too. Some say these are the muscles that prove to the world one is a bodybuilder, and frankly I can see why. Few things are more impressive in any physique than thick sweeping-wide lats. Not only are they important viewed from the back, but they’re also obvious and can essentially complement a quality physique from the front. Being a fairly large muscle-group, the lats need to be hit with a variety of exercises to achieve full development. Depending on the angle of different pull-downs and the width of the grip used with them, there are quite a few exercises that yield good results - provided they’re strictly executed - and which will be presented in the “exercises” section of this page.
The lower lats - provided they’re developed well-enough - can be extremely spectacular. They can give the latissimus dorsi that “cobra hood” appearance that looks just awesome on stage and in general.
Another - visually and otherwise - important piece in the upper-back puzzle is the trapezius. This triangular muscle-group, that links the latissimus to the neck and deltoids has already been presented in detail in the “shoulders” section, because, courtesy of its position, it’s rather hard to decide whether it belongs to the shoulders or the back.
The middle back is where the two sides of the latissimus dorsi come together near the spinal cord. This area of muscle is often overlooked by bodybuilders concentrating on their lat width. The thickness of this muscle sets the tone for the rest of the back to look awesome.
The spinal erectors are the lowest muscle in the back and quite probably the smallest as well. However, they fulfill one of the most important functions of every muscle-group. They protect the nerve channels and keep the spinal cord erect and protected from physical shocks.
Stretching becomes an important issue with the muscles of the back. Promptly executed stretches add to the length of the muscles and thus their volume as well.
Examples of great lats: as far as thickness and bulk goes, Dorian Yates is pretty much unbeatable in the lats section as well. Given the fact that his back is visibly thick even when relaxed, I reckon it’s fair to mention him here as the ultimate example.
In definition, though, Flex Wheeler is probably as unbeatable as Yates is in thickness. I couldn’t find a better example to illustrate muscle separation, striations and general back definition than Flex Wheeler.
Looking at back exercises I’ve taken the liberty of classifying them into two major groups: Chins and Rows. While chins are more suitable to developing the sweep and width of the lats (depending on the grip one chooses to use of course) rows are better for increasing the thickness of the lats and the middle back.
Here are the chins-based back exercises:

1) Chin ups executed behind the neck with a wide grip
2) Chin ups done on a wide grip bar to the chest
3) Chin ups done with a close grip bar to the chest
4) Pull-downs executed on a machine
5) Pull-downs executed on a machine with a close grip

The exercises based on rows are as follows:

1) Rows executed with a barbell in a bent-forward position
2) Rows done with the T-bar machine
3) Rows executed with dumbbells with one arm
4) Rows executed on a cable machine

Other back exercises ( not rows or chins based)

1) Pull overs done with barbell on a horizontal bench
2) Pull-overs executes on a machine
3) Deadlift

Exercises for the spine erectors :

1) Lower back extensions
2) Lower back bows