Why don't I fall down when I stand up?

Why don't I fall down when I stand up (physics, tensegrity and movement mechanics)?

One of the most fundamental forces that human beings are subjected to is gravity. Gravity is defined as the natural force of attraction exerted by a celestial body, such as the Earth, upon objects at or near its surface, tending to draw them toward the center of the body. It is the mutual attraction between two bodies that have mass. According to Einstein’s theory of general relativity, gravity is created by the curvature of space. However, the mass of a human is not significant enough to create any significant curvature of space. Any curvature created by a person’s mass is outweighed by the curvature created by the Earth’s mass. The series of developmental steps that humans go through as they progress from lying on their backs to standing on two feet is constantly driven by this massive pull on their bodies through the surface of the earth. That process in our early growth is our fundamental core training and stabilization.

This force becomes very relevant when looking at different aspects of muscle function. If we are standing up, the pull of gravity is going straight through us toward the center of the earth. The question then becomes, How come we aren’t always falling down? Buckminster Fuller’s tensegrity or floating compression model is a great way to visualize this. In a system with tensional integrity, isolated components in compression that are not touching each other are housed inside a net of continuous tension that delineate the system spatially. Image the skeletal system as the compression structure part of the model and the myofascial system as the tension net. A tensegrity structure has to constantly adjust due to the forces that are placed on it. Similarly, as we move, out soft tissue has to constantly adjust tension to keep the body upright. Tightness in the myofascial system is an artificial adaption to maintain the tensegrity balance when it doesn’t happen properly. It is a spontaneous evolutionary process of our bodies trying to help us out.

Gravity then, is a primary driver of movement mechanics and the musculoskeletal adaptions of the human body that result from motion. Both a preventative and a rehabilitative model must look at movement mechanics both in and out of the context of gravity. This is fundamental to determining if movement pattern limitations are primarily mobility restrictions, or stability (motor control) issues, or both. The reason is muscles are first and foremost reactors to motion. They desire to be turned on eccentrically first which is a result of motion that facilitates the proprioceptive system to decelerate the perceived motion. That is reflex stabilization. In order for the body to receive the correct information, joints must be able to go through their full ranges of motion. This mobility has to be tested outside the context of gravity to determine if it truly exists. If it doesn’t, the musculoskeletal system doesn’t get the information to appropriately control motion. As I mentioned in the blog post, "The joint by joint concept of movement", the body will move in the path of least resistance, which is the directional susceptibility of movement. Many times, the pathway chosen is a result of poor mobility, which causes compensatory relative flexibility and stiffness. Whatever language you want to use, be it phasic muscles being forced to do the job of tonic muscles, or prime movers being used as stabilizers, there is a shift in muscle function and how the body stabilizes itself so that movement can occur. As a practical example, if you have an anterior pelvic tilt that your core can’t control, your hamstrings will have to chronically contract to attempt to stabilize the pelvis. No matter how much you stretch them, they will reflexively shorten when you stand up or move. Motion dictates it.