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A Brief History in Biomechanics

For a Medical Disclaimer, please read it here.

Before we learn about the new Integrated Spring-Mass Model (AKA the Human Spring Model) of biomechanics, let’s take a brief look at the history of biomechanics. To understand this new model, you need to know we got here. I will quote writings from chapter #2 of Stoxen’s book for information on history of biomechanical models.


The first real biomechanics experts go back to Leonardo da Vinci in the 15th century and Galileo Galilei in the 16th and 17th centuries. It was Leonardo da Vinci’s discovery of the anatomy of the foot caused him to say, “The human foot is a masterpiece of engineering and a work of art.” Following da Vinci and Galileo came mathematicians Joseph Louis Lagrange, Daniel Bernoulli, Leonhard Euler, and Paul Thomas Young.

The first useable biomechanical model used by medical professionals was the Inverted Pendulum Model. It was created by Giovanni Alfonso Borelli during the Italian Renaissance. The core idea of walking in this model was that we use the body’s levers to take our first step, leading with a straight and stiff leg in the ground, and then employing the back leg to bring the rest of the body over the planted leg. This creates the traditional “heel-toe” walk.

Figure 1: The Inverted Pendulum Model


However, running was considered to be a different process in which the legs are bent while the body bounces off of them…kind of contradicting, isn’t it?


Even with this contradiction, this first model made Borelli the father of modern biomechanics, and his model is still the go-to for modern physicians.


As an expert in biomechanics, I side with Dr. Stoxen in refuting this model. The body’s lever movements are used in curling a dumbbell or picking up a box, but a lever action can’t possibly be used for absorbing the impact of running, walking, jumping, recycling energy, providing spaces for joints and the safe passage of blood vessels and nerves, etc.


A lever is a simple machine used to do work, not absorb energy. This leads us to a model created in 1989 by researchers at Harvard University, who understood how legs use more of a spring capability to absorb impact.


Harvard University scientists Blikhan, Cheng, and McMahon created the Spring-Mass Model in 1989-1990 to counter the popular inverted pendulum model. This new model represents the legs as springs and the head as the non-spring-like mass.



Figure 2: The Spring-Mass Model developed by Harvard University scientists


It was an improvement upon the inverted pendulum model, in that it better explained the absorption of impact and recycling of energy. This model shows that when walking or running, the muscles, tendons, and ligaments in our legs behave together as single, linear springs. The leg is assigned properties of a simple spring and describes the mechanics of running and other bouncing gaits remarkably well.

Yet, even though the researchers responsible for this model admitted to the spine acting as a spring, they left it out of their model. I’m not sure why, but the absence of the spine’s spring capabilities gives a reason as to why doctors have a tough time understanding how to treat disc problems and pain in the thoracic outlet.


This prompted the creation of the Integrated Spring-Mass Model, otherwise known as the Human Spring Model, by Dr. James Stoxen, DC, FSSEMM (hon).

Figure 3: The Integrated Spring Mass Model, aka The Human Spring Model


Stoxen’s Integrated Spring-Mass Model suggests the entire body is an integrated or connected series of springs, forming one giant torsion spring. The mass is the head because it has no spring capability.


Dr. Stoxen goes on to explain that the brain controls the tension on the body’ spring. In Stoxen’s Integrated Spring-Mass Model, the body weight loads into the ankle and foot spring like a sling shot.


The force of impact is loaded into the arch of the foot leaf spring and the rest of the load bearing spring mechanism by stretching tendons, which form a sling shot suspension system, thus storing the impact energy to be recycled for forward movement. This spring suspension sling shot mechanism stores energy into the foot, arch, ankle and lower leg while the calf muscles contract to tune the tension on the tendons to absorb the landing safely. It has been mentioned by Yuri Verhkoshanski that up to 60% of the energy needed to spring is recycled through elastic elements. Stoxen met and studied with Verhkoshansky at the National Institute of Physical Culture and Sports Sciences in Moscow from 1987 – 1989 where much of this integration of plyometrics (spring) into biomechanics was theorized.

It also mentions that the stronger the spring, the better the body’s ability to maintain healthy joints at greater speeds and body weight (i.e., loading forces.--F = M x A).


In 2015. Dr. Stoxen was awarded an honorary fellowship at the opening ceremonies at the World Congress of Sports and Exercise Medicine by a member of the Malaysian royal family, the Sultak of Pahang, mainly because of the development of this new model of biomechanics and the approach to examination and treatment that goes with it.

Big fans of his model are Dr. Robert Goldman, MD, President Emeritus of the National Academy of Sports Medicine NASM, Dr. Ronald Klatz, and others.


Dr. Stoxen describes the body as having seven floors of springs:

  1. Arch of the foot

  2. Subtalar Joint (just below the ankle joint)

  3. Ankle Mortise (where the shin bone rests on the ankle)

  4. Knee

  5. Hips

  6. Spine-Chest

  7. Head

This model has been implemented by Dr. Stoxen in his study, examination, treatment and prevention, and has been praised by doctors around the world. It has changed my understanding of the body’s engineering and has affected how I approach the design of our products, the training regimens of players I coach, and my own exercises. In the next segment, I will discuss this model more in depth and help you gain a better understanding of how it works.


Want to learn more? Get Dr. Stoxen’s Book “The Human Spring Approach to Thoracic Outlet Syndrome” on Amazon here.



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