If your head is pointed up you're basically hyperextending your cervical spine. To quote Rippetoe:
Eyeballs
Eye gaze direction is critical in all barbell exercises, and is the most commonly misunderstood aspect of squatting and deadlifting.
The chest follows the eyes, and the back angle
is the chest. It's very important to understand the role of the trunk segment in the mechanical execution of these two lifts in particular, and how the eye gaze direction can affect the physics of the lifts.
Since this is a deadlift article, we'll stay with pulling. If you look up, the vast majority of you will have overextended your cervical spine - your neck.
This seems probably counterproductive, considering the fact that the spine is best loaded in normal anatomical position, the way it's best configured to transmit force between the vertebral bodies spaced apart with intervertebral discs, who like to be loaded in compression the way they're designed to transmit force.
Your head actually weighs 5-8% of your bodyweight, and keeping your neck in normal extension maintains the position of more of your body's mass in front of the bar. It actually produces a longer back segment, some of which is then positioned forward of the bar.
We've already observed that you can't pick up a heavy object that's too far "in front" of you, and that more of your mass forward of the bar balances the alignment of the bar's center of mass and that of your body.
Keeping your head in line with your back maintains this mass relationship much better than an overextended cervical spine. This effect is obviously more important in a lighter pull, like a clean or a snatch.
Now, observe the anatomy of the traps. Note that it has an origin from the base of the skull all the way down to T12, thus making it the longest muscle origin in the human body.
Note that almost all these fibers insert on the spine of the scapula. The traps therefore support the scapula, which articulates with the arm, which holds the bar. The bar therefore hangs from the traps, which hang from the spine, from the base of your skull down to the last vertebra with a rib attached to it.
And you want to lift a heavy weight with the top one-third of your spine in overextension, with your neck curved like a hook? You should probably rethink this decision.
We've already explored the role of the back angle, so do an experiment. Stand up straight and look at the floor about 15 feet in front of you. Note your posture and the weight distribution on your feet against the floor.
Now, look up at the ceiling, the way your high-school football coach told you. "Look up, son! You gotta look up if you wanna go up! I said
look up, boy! Look up through the top of your skull!"
Our experience with this little test indicates that about 80% of you will feel your weight go to your toes. This is because your chest follows your eyes, and your back angle follows your chest, and you lean onto your toes to compensate so you don't fall backwards.
If this happens at the bottom of the pull (or the squat) when your knees and hips are in flexion, the result will be that the hips move forward a little, since "the back bone's connected to the hip bone."
And since "the hip bone's connected to the knee bone," the knees will move forward a little too. This closes the knee angle and distally slacks the hamstrings, which you're trying to use to support the moment arm on the hips.
If you have trouble in the middle of a pull, check your eye gaze direction and see if you're looking up. If so, try fixing your gaze on a point on the floor that holds your chest in the best position to use your back angle for the pull.
