TFL FUNCTION (Why Your Stick Figure Squat Is Wrong)
By Jake Larsen
Beginning with wrestling and soccer, Jake has been immersed in fitness nearly his whole life. Personal training and studying exercise in college were the natural progression of that passion. Competing locally in bodybuilding and powerlifting, Jake currently studies exercise at university and does online coaching at Jackalstrength.com.
TFL Function
(and why your stick figure squat is wrong)
You know all those stick figure images on the internet that try to break down the “essential biomechanics of a squat”, or any other exercise? Have you ever noticed that the people so interested in educating you on the importance of the biomechanical advantages of their stick figure squat positions seem to strangely resemble the stick figures they draw? Put simply, the stick figure “biomechanics” model is wrong.
There are no biomechanics to a two-dimensional image, it’s just mechanics (also known as basic physics) with no anatomy involved. Anyone who has ever taken an anatomy class has surely asked themselves at some point, “Why does there have to be so many strange terms to basic movement?” Adduction, external rotation, flexion, dorsiflexion, etc. Can’t we just say up and down? The truth is, a human moving in all three dimensions is significantly more complex than can be described with basic directions or stick figures. Let’s look at an example.
The infamous TFL.
A little muscle with a big impact. Called the Tensor Fascia Latae (pronounce that however you please, everyone does), the TFL originates from the anterior superior iliac spine and the anterior part of the iliac crest, then joins with the glutes to form the iliotibial tract, which attaches to the lateral condyle of tibia. It’s essentially a tiny muscle with a super long tendon that attaches at the hip and the knee.
In anatomical position (stick figure mode), the TFL performs abduction and flexion of the hip. That’s where the stick figure image ends. Because of the inherent (three-dimensional) anatomy of the TFL, as soon as you enter any form of hip flexion (i.e. squat) the function completely changes. Suddenly, instead of performing abduction, the angle of the TFL shifts and it performs internal rotation of the femur. The function of a muscle can change as the body moves! The TFL performs no internal rotation at all in anatomical position, but as it flexes the hip, it inevitably starts to internally rotate as well.
Why does the TFL and it's weird functions matter?
Because as soon as you start to squat, your TFL is trying to bring your knees together. At what point in your movement pattern you enter significant hip flexion can be an important factor, but if you’re reaching any decent level of squat depth, at a certain point your hips will be flexed and your TFL will be active.
Is your TFL tight before you squat? That will affect your performance. Is your TFL tight after you squat? Clearly something went wrong. No stick figure squat model is going to show you that. Exercise cannot be boiled down to a two-dimensional snapshot of singular function.
The human musculoskeletal system is not as simple as a stick figure drawing, but it’s not rocket science either. Take some time to learn basic anatomy/physiology. It’ll make you a better athlete or coach. You don’t need to be an expert in biomechanics to benefit from a little more knowledge of the human body!