You’ve heard it before. As you’re about to go into a squat or lunge, the instructor tosses out the gem, “Keep your knees behind your toes”. This has a history in the business of course, going back to a 1978 study done by Laughlin, Lardner, and Dillman (1) that demonstrated that by keeping a more vertical lower leg shaft and shifting the hips back more in a squat (or lunge), this created less shear force on the knee. Not that most people know the origin of this, but this nugget has been passed on since the late days of disco to present day in an impeccable display of longevity for something that has been proven to be lacking proper context and individuality in execution for the fitness professional, and by proxy, the fitness client.
This type of information exchange highlights an issue within the Social Cognitive Theory construct so often employed within the fitness industry. Albert Bandura’s Social Cognitive Theory, in it’s simplest form, is behavioral learning through observation, imitation, and modeling. A trainer learns from another trainer, viewing everything from client interaction and rapport-building techniques, to proper implementation of goal-oriented exercise programming, and client achievement through the accomplishment of meeting those goals.
The theory works quite well in most educational settings, although there are two assumptions being made that need to be considered:
1. That the person being imitated knows and fully comprehends what they are doing;
2. That the person imitating is gaining more insight into the proper application and procedure required to fully implement the above relationship with a client or class.
And this is where the game of telephone goes awry. People hear the correlation, that by preventing anterior shifting of the knees in a quad-based movement the knees are kept in a more risk-free environment, thus, allowing for healthier knees. Except, like most news headlines, it leaves out perspective on the whole story and leads to the misuse of information within the fitness industry.
In a study done by the University of Memphis in 2003 (2), research did indeed find that allowing the knees to drift forward past the toes placed 28% more shear force on the knees. Definitely something worth noting. However, in an attempt to keep the knees in a hypothetically “safer” position, this placed over 1000% more stress on the hips. That’s not a typo.
Just as a reference 1000 > 28. By like a lot.
Here is some context. One of the things you learn about the knee joint is that it’s really just along for the ride when it comes to leg mechanics. As the Gray Institute tells its students, the knee is stuck in the middle with nowhere to go. In most situations with the knee and knee injuries, the fault comes in the form of a bottom-up driver, meaning there is something going on in the foot/ankle complex causing a corresponding issue at the knee, or a top-down driver, meaning there is an issue at the hip complex placing misaligned stress on the knee.
No matter what the driver, placing 1000% more torque on any joint system is typically a training no-no, especially when it’s done on purpose. It may have a specific place for a specific person, as you can never say never to anything, but in general, artificially placing that much torque on the lower back and hips is unnecessary. The idea of “keeping your knees behind your toes” demonstrates the partial knowledge nuggets that get passed along in fitness. These statements are used as “truths” when in reality it is incomplete information being misrepresented and misused, and as such, becomes invalid without consideration to the whole individual. We are incredibly complex, integrated structures with unique functional capabilities, why are we limiting ourselves to rules instead of exploring possibilities?
To those newer to the fitness profession, don’t accept information without doing your own research and gaining more perspective on how this information should, if at all, be utilized. In reality, most professionals out there are regurgitating “knowledge”, giving a misrepresented “how” and not understanding the “why”. If you don’t know how or why, look it up. If there are conflicting answers, read both. Most often the answers are not a matter of right or wrong, but of understanding how to properly apply ideas and concepts in the best way for our clients. We have a responsibility to those who come to us for guidance to provide them with as much perspective as we can, to put them in the best possible scenario to succeed. Be better. Question everything.
Oh, and for those wondering what a good cue is for squatting or lunging, encourage your clients to keep their upper body as vertical as possible and wherever the knees may go, they go.
MCLAUGHLIN, T.M., T.J. LARDNER, AND C.J. DILLMAN. Kinetics of the parallel squat. Res. Q. Exerc. Sport 49:175–188. 1978.
Fry, A.C., Smith, J.C., and Schilling, B.K. Effect of knee position on hip and knee torques during the barbell squat. J Strength Cond Res. 2003 Nov;17(4):629-33