Biomechanics is the application of physics to the human body. Yet it seems as though there are gaps between our understanding of physics, our understanding of human movement, and its application to sport, training, and coaching.
There’s a lot of conversation revolving around topics like velocity based training, ideal force vectors, activation of, and forces imposed upon, individual muscles, horizontal vs. vertical forces in sprinting, etc. but we still cannot seem to explain certain feats of athleticism.
The topics listed above are just examples, but illustrate a point: We place importance on the factors we can measure and easily observe.
The truth lies underneath the surface, and some great coaches are digging into a new view of physics and the core of human movement. I’ve come across several huge ideas in the last few years that have connected the dots in such a way that a new paradigm of biomechanics seems to be sketched in the horizon.
Before tying everything together, I want to introduce these ideas and their importance.
The Importance of Proximal to Distal Activation Patterns
Douglas Heel’s Be Activated System was a game changer for many coaches in all realms of sport. The Be Activated model revolves around the concept of three different “zones” of musculature that dictate our functionality in movement.
Without going too deep into the details of the system, Zone 1 muscles are the psoas, glutes, and diaphragm; Zone 2 are upper leg and trunk muscles; Zone 3 are upper body and lower leg muscles. Optimal movement comes from a Zone 1-2-3 activation sequence.
Many coaches took on this system, got great results, and gave raving reviews. As such, this model illustrates a hugely important point that ties in to a few other key ideas, and requires further examination.
Neuro-fascial System
The role of fascia in movement has always been a highly debated and somewhat mysterious topic. Highly elastic in nature, and heavily integrated into the neural network of movement, the neuro-fascial system helps explain the importance of a proximal to distal activation sequence.
As our connecting piece of anatomy to the ground, our feet play a massive role in the facilitation of tension through the neuro-fascial system. Our feet have an astonishing number of afferent neural connections that reflexively communicate tension up these neuro-fascial pathways. How our foot strikes the ground therefore plays an important role in where the tension goes.
Rotational Dynamics in Arthro- and Osteo-kinematics
At the level of the joint there is no such thing as linear movement. There are muscles that pull on tendons that pull bones in arcs and circles. By understanding this, we can see linear motion as a finely choreographed sequence of arcs and rotation, that when pieced together create a straight line.
When looking at movements pieced together in this way, we can see the importance of rotation in the creation and transfer of energy in movement. An important concept from Adarian Barr’s work is the role of end range of rotational motion in timing and energy transfer.
As an example of this concept, look at how energy gets transferred through the kinetic chain in a baseball or javelin throw: Energy of internal rotation of the right side of the pelvis gets stopped and absorbed by the stiffness of the left hip (think about a bicyclist crashing into a curb and flying over the handle bars to help visualize this example). The linear and angular momentum of the body causes this energy to get transferred up the spine, where end range of thoracic extension and rotation acts as another “curb” that transfers energy to the scapula.
Jan Zelezny is the epitome of these motions in action
The end range of scapular retraction and posterior tilt acts as another “curb” that forces gleno-humeral external rotation. When the shoulder hits its end range of external rotation, it acts as a “curb” for the transfer of energy into elbow extension, whose end range acts as a “curb” for gleno-humeral internal rotation and forearm pronation.
There are three key takeaways from this example.
First, as noted above, is that individually these motions all occur in arcs and rotations, but synergistically pull the baseball or javelin in a perfectly straight line.
Second, is that at these “curbs,” the mass of each lever gets progressively smaller, so the conservation of angular momentum plays a massive role in accelerating limbs to high speeds.
The third is that the end ranges of these joints act as a built in “timer” for movement. If you have adequate mobility, and the ability to stay relaxed, each joint will perform its actions when the force gets there.
Timing, Waves, and Elastic Energy
Muscles, tendons, and fascia are all intrinsically elastic. The stretching and contracting of these elastic tissues can be looked at as waves of tension. Remember back in physics class, how all waves followed a sine function when analyzed on a graph? The same concept can apply to stretching and contracting muscles/tendons/fascia.
Building on this concept, when two waves “collide” they can either be constructive or destructive. That is, they can either add together, or cancel each other out.
Whether they add together or cancel out is a function of timing.
Utilization of Nature’s Potential Energy in Movement
Too often we think of movement as how our body must overcome the forces imposed by Mother Nature. After all, gravity is the enemy of jumping high and lifting heavy.
But all of these concepts just mentioned allow our body to integrate these forces into efficient and powerful movement.
To start, the overall connectedness of our entire body through the neuro-fascial system creates a large “pool” of elastic potential energy to be utilized. How do we tap into this pool?
In order to initiate the stretching of muscles/tendon/fascia, we need to “load” the body from the ground up. This is easy to do in the weight room, where a barbell can be thrown on your back, but where does the “load” come from in natural movement like running and jumping? Gravity and momentum.
This is a concept that Adarian Barr talks about when breaking down asymmetrical movement. One side of the body gives energy, while the other receives energy.
This is why a long last step is crucial for jumping and throwing. It creates more momentum to load the entire elastic system. The lightning fast downward arm swing of the best jumpers utilizes downward momentum to contribute to loading the elastic reflex. The purpose of the “soft step” back foot contact in the javelin throw is to guide the momentum of the center of mass directly into the block leg. The farthest throws come from the best block leg loading.
We also have to consider that the general shape of our body allows for incredibly efficient passive transfer of energy. As mentioned previously, the fact that proximally to distally our levers and limbs decrease in mass allows for incredible acceleration through the conservation of angular momentum.
We know that that hip extension and knee extension are intrinsically linked, but this also integrates into what we know about elasticity, and can even be related to hamstring demands in sprinting.
When the glute extends the femur the angular momentum at the knee joint will naturally cause the knee to extend. In sprinting, the timing of this is such that the knee reaches extension just before foot contact, pre-tensing the hamstring for the elastic stretch at foot contact. When the foot hits the ground, the entire posterior chain gets loaded, and because of the angular momentum at the knee, the hamstring must deal with incredible amounts of eccentric stress.
The foot also needs to be talked about in this section, as its shape provides several key properties that allow for translation of gravity, momentum and ground reaction forces into powerful and efficient movement.
First, is that because the foot is a first class lever, and because of the general shape of the bottom of your foot, which allows it to “roll,” it has an intrinsic forward and upward force vector. This vector can be changed depending on knee angle and hip rotation.
Second, is that the arch of the foot itself is highly elastic, and can provide an extra “spring” in movement for people who aren’t flat-footed. This elasticity from the arch is integrated into the posterior chain just as the Achilles or hamstring is.
Third, as just mentioned in the first point, because of the arch and because of the ability to lift our toes, the foot can utilize the body’s own weight to accelerate by “rolling” from flexion to extension and pronation to supination. The key is that the foot needs to be strong enough to maintain its shape through these movements.
One last piece of the puzzle to tie all of this together is that of timing. Precision in timing is the single biggest key in powerful movement.
As mentioned above, the transfer of energy proximally to distally occurs in waves. This can manifest in the form of a transverse wave up or down your body from joint to joint, or in the form of a longitudinal wave through the elastic elements of your body.
(Transverse and longitudinal are the physics terminology for how different types of waves travel. Transverse would be like wiggling a rope so it looks like a sine wave, while longitudinal would be like if you quickly compressed and retracted a slinky and you’d see the line of compression travel down the coil.)
A transverse wave up or down the body comes from the conservation of angular momentum, just like in a whip. The key to allowing this to occur is to have adequate mobility and relaxation to let the wave passively pass through each joint.
A longitudinal wave of elastic energy comes from loading and unloading muscle/tendon/fascia. Neurofascially facilitated vertical stiffness is a major component of allowing these elastic waves of energy to travel up the body. Without full body connectedness, there is no spring and movement becomes driven by muscle.
The key to true athleticism is in timing of movement so that waves of energy combine, rather than cancel each other out. The single best example I know to visualize this is in the video below of Thomas Rohler throwing the javelin.
When his block leg hits (also notice how he directed his CoM straight into his block leg off the back foot contact), you can literally see the ripple of force travel up his leg. That “ripple” is elastic energy traveling up his posterior chain and into his torso.
But what’s more important in why this throw went so far is his timing in creating stretch across the rest of his body exactly at the moment his block leg hits. While the stretch from hip-shoulder separation is still unloading, he creates a stretch across his chest with contralateral arm extension. Then just as the t-spine squares up into the throw (meaning its stretch-shortening cycle is complete, and angular acceleration of upper body is at its highest value), and the chest begins unloading its energy, the block leg hits and the acceleration from the massive wave of elastic energy combines with the acceleration from the rest of the elastic energy to synergistically launch the hand and javelin full speed ahead almost 90 meters.
If you can’t appreciate the javelin example, the same thing can be seen in the jump below.
The first thing to notice here is that he has a long penultimate step. This gives him a ton of momentum to load the leg into the jump. The pathway of energy after the penultimate is where things are a bit less intuitive and helps to explain a lot of the concepts already discussed.
The key to this jump is in the transfer of energy from the long penultimate to left leg contact to right leg contact. When the left leg hits, it acts to translate the some of the forward momentum of the penultimate into rotation of the pelvis – which, while hard to see in the slow motion video, creates a lot of angular acceleration – and to guide the CoM into his rigid takeoff leg. This is also a tremendous display of vertical stiffness through different athletic positions, allowing for the wave of energy to travel up through his body.
The power through this jump doesn’t come from strong muscles or insane speed. The power of Rohler’s throw doesn’t come from having a “powerful arm”. The power comes from the synergy found in using the levers, joints, and elasticity in the body to utilize the forces of nature instead of fighting them.
A New Perspective in Biomechanics
To summarize:
- The most important aspects of movement may not be measurable or easily observed
- We can still optimize movement based on understanding of movement principles
- We must take a closer look at how our body integrates the laws of physics versus fighting them
The fact is that our current perspective of biomechanics does not explain everything we see in sports. I’m personally tired of hearing about genetics and steroids and fast twitch muscle fibers. There is so more to the story.
This is meant to be a look into some of the factors that we are overlooking, a small piece of an explanation yet to come. There are incredible coaches working to shift the paradigm of how we see movement, and your job in all of this is to stop blaming your genes and to look under the surface yourself.
About Kevin Foster
Kevin is a former Division I javelin thrower for the University of Connecticut. He is currently training to compete post-collegiately while working as a personal trainer and javelin coach in Southeastern Connecticut.
He runs the Javelin Anatomy Instagram page whose mission is to break down and simplify the anatomy and physics that go into the javelin throw in a logical, critical, and holistic manner. Follow the page @javelin.anatomy to learn more about the science of javelin throwing and training. For any questions or feedback, email javelin.anatomy@gmail.com.
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