Training back has a couple of aspects that add a little more challenge to the work out. First, you can't see it (excepting the side of the lats), and second, there are quite a few different muscles that need to get hit, and to do so one has to pull at different angles, or really focus on that or those muscle to engage them as primary movers of the lift being executed.
How can you see the back without having a visual cue? In Immanuel Kant's "Critique of Pure Reason", he argues that the concept and experience of space is a priori, that is we have the knowledge of space prior to experience of space. In order to even move, we have to have knowledge that there is a possibility of 3 dimensional movement. We hold in our imagination a representation of space. The key points are imagination and representation. I will apply these notions later, but keep them in mind, if not the forefront, at least the back burner.
Spinoza took the notion a bit further while arguing with a fellow philosopher concerning knowledge of what you cannot see. Spinoza posited that one must have knowledge of what one cannot see since one just knows that there is something behind you. His friend (who I want to say was David Hume given the counter argument) argued that if you cannot see a thing one cannot know it's actually there, which has a philosophical problem. If you, of necessity, cannot know something is there, for example, the floor continues to exist even of you cannot see it, then one could not even move without first looking to see if floor exists.
To illustrate and exemplify Spinoza's position of a priori knowledge of things not seen thus their existence in space, imagine that you are sitting at a table doing something on your computer such that your attention is nearly unbreakable. A friend comes into the room and asks you to toss him or her the pencil that is on the table behind you. You reach behind you while still attending to the task on the computer screen, fumble around a bit until you find the pencil. Once you have the pencil, you toss it to the front-right of the room where you imagine your friend to be waiting for you to toss the pencil. You toss it that way, and it lands just shy of your friends grasp.
So what happened here is something we take for granted every day all day long. First our example knew she could operate 3 dimensionally given that she moved her arm behind her, Next, she was able to differentiate the shape of a pencil say from a stapler, a paper clip, or a coffee cup. Thus, the pencil existed without her seeing it. She had in her mind, as a mental state, the representation of a pencil in her imagination. You can see how the two notions come together into one action. A priori knowledge of space, representation of an object in space in the imagination, and the desired action to complete the task at hand.
Let's now take this position to Back Day. We all know that we have a back. Whether we've seen it or not, a simple discomfort in any area of the back is pretty good indication that there is something there. I'm sure most, if not all of you have seen YOUR back. (One may argue in a hair splitting way as philosophers like to do that even though you've seen your friends back, how do you know you have one! Ridiculous, but that's what philosophers do, and all too often if you ask me.). On back day, we are faced with the challenge of engaging the muscles that we cannot see. As humans, we largely depend on environmental visual cues to execute many actions, and many of these visual cues are subconscious. Let's take the steps, in seriam to get a picture as it were of your back during your workout using the ideas promulgated be Kant and Spinoza.
First, we need a representation of the back held in our imagination. One way to start this process is to look at illustrations of the back. I like to use an anatomy book, and pictures of bodybuilders with exquisitely defined backs. I may, too, look at illustrations that show what action each muscle in the back is designed to accomplish. That way I have a "moving" picture represented in my imagination to reference when I am doing a certain exercise where a specific muscle is the intended target. Off to the gym...
So, here we are, at the gym, well hydrated, and ready to crush back day. We do some warm ups, and, for the sake of argument, decide to start with chest supported rows. I've chosen this particular exercise as one can really feel the stretch at the starting position, which brings me to my next point; afferent nerve stimulation. Armed with the representation in imagination of the upper back and lats, we assume the position on the machine, lift the weight off the catch, and allow the weight to lower towards the floor. Feeling the muscles stretch from the pull of the weight in gravity, we now have knowledge through sensation from the afferent nerves telling the brain there is some level of discomfort. In order to get sensation from muscles, we need to activate the nociceptors, which relay a message vis-a-vis the sensory-motor cortex that there is discomfort in a certain area. Now we can map on the sensational representation on to the imaginary representation, and pull the weight up nice a slow. I suggest keeping your eyes closed during the exercise. Keeping awareness on and with the muscles of desired engagement, pull the weight, and once at the top, squeeze and hold the weight. Now, keeping the biceps flexed and holding the weight in position, move only the back muscles for a few short reps, and hold the squeeze at the top of the concentric phase of each rep. Notice that the movement is small, or short. Now you may feel burning, which gives us even more knowledge through sensation, thus giving even a clearer picture of the back, and what muscles are used to move the weight. Lower the weight slowly, paying attention to the muscles that are doing the work. A few reps in, and you may feel a pump that may have eluded you in past workouts.
So, that's some philosophy applied to training tactics. My hope is that it helps with your back day. Maybe you have some way or manner of nailing back day that engages the mind-muscle connection too. I would love to hear what any of you folks do to achieve this important aspect of our beloved activity :)