by Jon Gilson

Successful lifting depends on four elements: area of base, center of gravity, combined center of gravity, and torque. If the aspiring coach understands the relationship between these elements and how they inform technique, the quick identification of faults and their respective remedies becomes automatic.
Area of base is a simple concept. It is the field delineated by the outside of the athlete’s feet and the space between them, length and breadth. It changes in size based on foot position, but is always rectangular.
Center of gravity is the point within any body around which its mass is evenly distributed. For our purposes, we can think of it as the point on which gravity acts. While coaching, we must worry about three separate centers of gravity: that of the athlete, that of the object lifted, and that created when they are joined together (the combined center of gravity).
The simple question: are my centers of gravity as close to the center of the area of base as the movement allows?
At rest, the athlete’s center of gravity lies somewhere on a vertical line between the pelvis and the navel and just dorsal of the frontal plane, its exact location dependent on gender and individual anthropometry. The object’s center of gravity lies in its geometric center, assuming it is of constant shape, i.e. a barbell rather than a sandbag or water-filled keg.
The combined center of gravity of the two lies somewhere on the line between the athlete’s center of gravity and the object’s center of gravity, biased closer to whichever weighs more.
Finally, torque is the tendency for a force to cause rotation around a fixed point. When lifting, our primary concern is torque about the hip caused by gravitational pull on the combined center of gravity.
Our objective in any lift is to move an object exactly opposite gravity and to hold it in its highest position for an acceptable period of time. To do so, we must vertically align our three centers of gravity (athlete, object, and combined) with the center of our area of base, minimizing torque and thereby maximizing efficiency.
Faults arise when these conditions of vertical alignment are not met.
Let’s look at some examples. In examining the explanations below, note that the combined center of gravity must always remain directly over the center of the area of base or the athlete falls over, so combined center of gravity is never the root cause of an error when the athlete remains standing.
Example 1: Object COG Forward

In the picture above, the barbell’s center of gravity is well forward of the center of area of base, causing the athlete to shoot the butt backward in an effort to keep the combined center of gravity where it belongs, directly over the center of the area of base. This results in a forward inclination of the torso, creating torque at the hip, and making a return to standing unnecessarily difficult.
To minimize torque, this athlete must bring the barbell within the area of base by lifting her chest. Her hips will come forward, resulting in a more favorable alignment of all three centers of gravity (athlete, object, and combined) with the center of the area of base.
Example Two: Object COG Rearward

In our next example, we see that the athlete has pushed the bar behind the area of base. Although we cannot see the area of base, we can infer that it is forward of the barbell, as the athlete has pushed his mass forward to keep the combined center of gravity over the center of the area of base. The torque on his shoulders is clear.
To minimize torque, the athlete would tighten the abdominal muscles and bring the bar forward, resulting in the alignment of all three centers of gravity (athlete, object, and combined) with the center of the area of base.
Example Three: Athlete COG Backward and Object COG Forward

The athlete above presents an interesting situation, in which the bar is forward of the center of the area of base, and the athlete’s center of gravity is backward of the center of the area of base. These faults result in a combined center of gravity directly over the center of the area of base, as predicted. They also create a tremendous angle at the hip, putting torso perpendicular to the direction of gravity and nearly maximizing torque.
To correct this situation, the bar would be pulled against the shins while the hip was simultaneously lowered, bringing the object’s center of gravity and the athlete’s center of gravity over the center of the area of base.
Example Four: Proper Alignment

Here, we see an error-free lift. The athlete’s center of gravity is just behind the center of her area of base, and the object’s center of gravity is just forward of the center of the area of base. Alignment is limited only by the fact that her body is in the way, and torque due to gravity is minimized.
Although the rules of center of gravity, area of base, and torque are not the only ones that inform proper technique, they are very handy in spotting faults. The simple question: are my centers of gravity as close to the center of the area of base as the movement allows? If not, the coach has work to do.
Tanya demonstrates good understanding of our principles, keeping everything vertically aligned at CrossFit Montclair. Pictures courtesy of Patrick Cummings.