Biomechanics Do Matter!

We need to have very strong primary movement patterns,
​and also the resiliency to deviate outside of those patterns! 

​In the post below, I am going to discuss CrossFit world champion Tia Toomey's 1 repetition max (RM) clean and jerk from the 2019 Crossfit Games. When watching the lift, it is apparent that her knees move into valgus (collapse inward) while accelerating upward from the front squat. I am using this video in particular because it has gained some attention as an example where movement biomechanics are not related to pain. In other words, the video demonstrates that a high level performer can have a ‘movement dysfunction’ without any pain. While this statement is absolutely true, it is important to take a broader perspective when discussing the multi-faceted subjects of pain and biomechanics.

​Watch the video below and continue reading!

Context is Everything

When analyzing movement, context is everything. In this video, Tia Toomey is performing a 1 repetition max lift at the Crossfit Games. The context is a very heavy lift with very high stakes. In these moments of maximal output, we see the extremes of human potential and the capacity of the human body to find any possible strategy to succeed. Her two options for this movement are 1. fail the lift or 2. win the event. Tia Toomey utilizes knee valgus on this lift because it is an all out, 100% max effort event. Under normal circumstances Tia Toomey does not valgus every time she squats. If you watch her front squat on a non-1RM lift, her form is biomechanically clean and efficient. Valgus doesn't cause pain, but let's not confuse it to be a good movement pattern.

You may notice that I use the word efficient. Below, I will discuss how movement efficiency minimizes stress and strain on our tissues.

Biomechanics of a Squat

Good biomechanics refers to our ability to use our anatomical levers, pulleys, and springs to minimize the physical stress placed on tissues & maximize the energy efficiency of the movement.

Squatting is a complex motion; and therefore, it has complex biomechanics. Many joints equals many parts simultaneously moving. For this reason, breaking down the squat into phases, joint actions, and muscles simplifies the equation.
​
During the deceleration phase of the squat, the knee flexes as the hip flexes. With knee flexion, the tibia naturally and involuntarily internally rotates. This is commonly known as the unlocking phase of the screw-home mechanism. Tibial internal rotation provides access to the subtalar joint and medial arch of the foot. This trio of joint motions- knee flexion, tibial IR, and controlled subtalar pronation- are important because it unlocks all the main rotational joints from the floor to the core. These movements are functionally significant because rotational leverage is our means of generating torque and power. During the squat, the quadriceps, adductor magnus, and glutes are our prime movers. Using good mechanics, including but not limited to a hip hinge, knee flexion, and ankle dorsiflexion, allows for these muscles to function at an optimal muscles length to tension relationship. Good biomechanics don't waste extra metabolic energy. They are efficient!

Toomey's Biomechanical Analysis

The Set-up Position: Deceleration Phase
In the Toomey Technique video, she loads the weight properly down into her squat (see picture right). Toomey maintains an upright spine, good hip to ankle alignment, and strong posterior chain tension. Her proper mechanics during the deceleration phase allow her kinetic chain to load symmetrically and maintain her center of mass over her feet. This is important because we are our strongest when rooted over our center of gravity. Additionally, this position maintains stability around the pelvic ring, which functions to disperse forces throughout the body. Maintaining integrity through the pelvic ring allows the sacrum to wedge deeper into the ilia, which creates a more stable base to generate torque from. 

​This wedging mechanism is the reason that the sacrum is shaped like an upside down triangle. As load increases, the ability to balance force and form closure of the SI joints becomes increasingly important.

---

Maximizing Elastic Tension
From her bottom position, she then lightly bounces the weight 1x to take up more posterior chain tension and position herself directly under the bar. Then, Toomey uses the timing of the bounce to accelerate and spring herself upward. Much like a loaded spring, the bounce and catapult action leverages the elastic components of her myofascial system. 

If the bounce was removed, she would lose her kinetic energy and momentum would be lost. The kinetic energy would turn into thermal energy absorbed into the tissues. Too much heat leads to stress on the tissues and fatigue is felt.
 
Load and Explode: Acceleration Phase
As Tia Toomey accelerates from her light bounce, the weight of the bar is near her maximal myofascial force capacity. For this reason, Toomey’s hips adduct and internally rotate as she pushes herself upright. This creates the valgus position at her knee and momentarily puts her joints in a relative closed pack position. The valgus compensation functions as a means to seek stability. She momentarily ‘locks’ her joint structure so that her muscles can pull through the most challenging range of the movement. 

The transition from up-phase 1 to up-phase 2 (pictures below) utilize all the built in rotational torque of our joints. The transition from pronation, tibial IR, and femoral IR TO supination, tibial ER, and femoral ER was controlled. These joint motions essentially ‘screw home’ the movement up the entire chain. The knee valgus is Toomey’s strategy to find stability in the low phase of the front squat to complete the goal-directed movement.

So...Is Knee Valgus Good or Bad?

I would argue that asking ‘good or bad’ is the wrong question. When discussing valgus (and all ‘movement faults’), we must have a clear definition of valgus. So, what is knee valgus? Is knee valgus from femoral internal rotation or femoral adduction and/or a flat footed posture? What degree of alignment do you classify valgus vs. normal alignment? And, maybe most importantly, does your client always squat with valgus or is it because of their current context? These contextual factors are essential to determining quality of movement and likelihood of injury. 

With that being said, typically valgus positionally inhibits the glutes, impinges the anterior hips, and collapses the arch. It is not a strong position and it locks out regional joints. These consequences of valgus decrease our degree of freedom, which could increase a person's risk of injury. For Toomey, the valgus is an exaggerated position of the normal mechanics. As her hips clear her knees, the knees return to their original stacked position. Since the technique video is a 1 rep maximum lift, it should be expected that her form and mechanics will be pushed to the limit.

In my opinion, valgus should be a movement strategy that we can tolerate, but it should not be our primary strategy.

Closing Thoughts

It is well established that isolated movement faults do not cause pain. However, this does not mean that pain and movement biomechanics are unrelated. How we move determines where physical stress transfers into our body. If I squat on my toes, I use my quads to a greater degree. If I squat on my heels, I am more likely to engage the posterior chain. In either scenario, some tissue is going to take on stress. Stress creates disturbance and imbalance, and too much stress of any kind decreases our recovery capacity and increases our risk of injury.  
 
When someone chooses an inefficient movement as the primary strategy, the joint mechanics, muscle-length tension, and torque capacity all suffer. Does this cause someone pain? No, not in the moment, but it adds stress into the system. We need to have very strong primary movement patterns, and also resiliency to deviate outside of those patterns!