The Physics of it All: Managing Center of Mass

We’ve been talking a lot about biomechanics lately, but we need to anchor into the output of it all! So let’s back up and recap a bit:

• The foot-and-ankle complex (FAC) is the foundation of force - most movements need a strong foot to transfer force to the knees, hips, and spine. Strong, stable feet mean lower barriers for gains!

• The lumbopelvic hip complex (LPHC) is the base of the spine. Control and strength in the LPHC means the transition of forces is smooth, and a healthy LPHC means you can do more, and get stronger and fitter without worrying about hip problems.

• The scapulothoracic complex (STC) work like the hips, but have a lot of natural considerations for our lifestyle. A coordinated, mobile, and strong STC create lower barriers for improving upper body strength and functional transfer to daily life

These are individual areas of the body, but they are all connected - changing one thing is likely to affect the other. Stable FAC means the LPHC is likely to naturally reposition itself instead of creating compensations, which affects the STC as well. So how do we know when the effect of these changes is going right? 

Center of Mass and Base of Support

Physics describes everything that the body is trying to accomplish in the gym, from how it compensates to how it produces the maximum force for a given movement. When we are coaching, we want to consider what your body is doing to make sure that the force is going through the correct area of the body. When we correct or focus on strengthening something in the FAC, LPHC, or STC, we are trying to orient the body to keep the central point of your mass in the correct spot for a given movement. The center of mass is defined as the point of an object where mass is distributed evenly, or in other words the average center point of the mass of the system. This is a singular point on all objects, and in the human body the center of mass lies inside of your belly, just behind the naval. No matter what you are doing, it is in the same spot as shown in Figure 1. 

Figure 1: Center of Mass 

Our body size and shape will modify this slightly, but in general this is the point of the body that we watch when we are looking for whether or not you are balanced over what is called the base of support (BOS), which is the area that your body is in contact with the ground or other objects, like  a bench. Figure 2 shows us that the base of support, when standing or carrying something, is our feet - the wider our feet, the larger the BOS. In this figure, the “Center of Gravity” is labeled because the person is holding onto a weight, which is shifting where the center point of mass is for the whole “system” (system = person plus weight). 

Figure 2: Base of support as it relates to the line of gravity and center of mass

Continuing with the example in Figure 2, we can actually start to tell what muscles are needing to work harder. In example A, the COM is inside of the BOS, so he is relatively balanced. The 3 pillars (FAC, LPHC, STC) are all distributing weight evenly to give both legs a relatively even amount of load to support. He’s probably feeling this weight in his quads, glutes, and core the most. In Figure B, the man is leaning forward, and the center point is now leaning forward, meaning his front leg is taking most of the weight, and he’s even standing up a bit more. The back is now taking a lot of the weight, but we would still consider this to be moderately “balanced”, if at the very least very difficult on the front leg and back. In C, he is no longer balanced - rather, he is completely leaning forward outside of his BOS. Two things will happen, either he will start walking forward to maintain balance, or he will fall over and drop the weight. He’s likely experiencing a large amount of low back tension, and we would consider this to be poor-form for actually picking something up, if not at a high risk of injuring his back.

The base of support as it relates to the center of mass determines the efficiency of a given movement pattern. I would consider A to be significantly more efficient if he is just trying to hold the weight, but if you are trying to move forward or expose the front leg to more force, then B may be more appropriate. So at the end of the day, the movement we select has to be for a particular purpose and the intent behind what we are doing is what determines the effectiveness of the exercise, as well as what we are actually cueing to get good “technique”.  When you are squatting, we want the COM to stay centered over the BOS, and move in a completely vertical line. If anything varies, we look at what the body is doing, adjust the FAC, LPHC, or STC as needed, then see what effect is had on that pathing. 

It’s just physics :) 

References: 

Volkmar, M. (2021, July 24). Center of mass management: A missing link in your assessment toolkit? Monika Volkmar Bodywork and Movement Education. https://www.monikavolkmar.com/2021/07/24/center-of-mass/ 

NeuroLab 360. (n.d.). Base of support and how it impacts balance. Retrieved September 10, 2026, from https://www.neurolab360.com/blog/base-of-support-and-balance-training