Please enjoy an excerpt from my book, Winning the Injury Game, which will be available soon.
Katy Bowman, a well-renowned movement biomechanist, has a great discussion about loads in her book, Move Your DNA.1 If you are into this sort of thing, definitely check it out. In her example, she demonstrates several ways to carry 13 pounds of pumpkin. Whether she is carrying one large pumpkin or several small pumpkins, the position in which she carries the fruit determines the load on her body. As she explains, the load is not the 13 pounds of pumpkin, but rather the act of carrying it and the forces that are created when she moves. Carrying the pumpkin on her head will create a different load through her load-bearing joints than holding multiple pumpkins in front of her body or balancing the pumpkins at her sides. As Bowman says:
Every unique joint configuration, and the way that joint configuration is positioned relative to gravity, and every motion created, and the way that motion was initiated, creates a unique load that in turn creates a very specific pattern of strain in the body.1
When you are in aligned posture, the unrelenting, downward force of gravity is sent through your bones, making them stronger. Yes, good posture helps to prevent osteoporosis. However, when your body alignment deviates from this ideal, your muscles take on additional postural work, even before you move. You are no longer using your bones for support. The work of holding your body up is largely transferred to your muscles. Just looking at the image of my misaligned side view posture below, you can imagine the additional stress that is being placed on my lower back and neck muscles just to maintain an upright position against gravity. My lower back and anterior (front) neck muscles are shortened, while the opposite is happening on the other side of the body—my posterior (back) neck and abdominal muscles are lengthened. These muscles can’t relax when I’m upright, so they just become tighter, more immobile, and more painful.
Now take this distorted static posture into movement, and I’ll have problems because of the forces generated through the joints as a response to the load of the activity. For instance, hiking creates a load on my joints as my body weight is carried through space. The hiking movements create forces that are transmitted throughout my body. When my hip and knee joints are not aligned correctly, these forces, including gravity, will be directed through the joints at awkward angles, causing increased strain, breakdown, and inflammation in the soft tissues (including the cartilage) that surround the joints.
In most sports, however, force is also coming from the ground up. This upward force is referred to as ground reaction force (GRF).2 GRF counters gravity and body weight, as shown in the figure to the right. For example, when we hit the ground while running, which is an integral part of many sports—soccer, baseball, basketball, ultimate Frisbee, triathlon and more—the ground hits us back, as explained by Newton’s Third Law of Motion: “For every action there is an equal and opposite reaction.”2 If this upward GRF encounters a postural deviation or “weak link” in the body, such as a knee or hip that is rotated inward or a back that is overly arched, pain and injury can develop in this area of the body.3
- Bowman, K. (2014). Move Your DNA. Restore Health Through Natural Movement. Carlsborg, WA: Propriometrics Press.
- Romanov, N. (2008). Pose Method® of Triathlon Techniques: Become the Best Triathlete You Can be 3 Sports – 1 Method. Coral Gables, FL: Pose Tech PressTM.
- Dryer, D. [Chi Running]. (2009, February 23). How to Avoid Heel Strike: Video Instruction by Chi Running’s Danny Dreyer. [Video file]. Retrieved from https://www.youtube.com/watch?v=rkUqkdPQHis