How low can should you go ?

So I’ve recently been asked a questions during Momentum’s weekly Friday instagram Q&A, where thousands a few people tune in and ask some questions about training, nutrition, performance or other health related questions…..mostly……. weirdos ! -_-

ANYWAY….let’s get to it.

The question I got was:

“To parallel or below when squatting?”

Heinrich “Milo” Steinborn.

I could discuss the history of squatting, Milo (Heinrich) Steinborn, acknowledged for his physical feats and most notably the Steinborn squat (google that, interesting to say the least), the “deep knee bends” exercise, its evolution into weighted full depth squats and it’s rise in popularity.

I’d also have to mention karl klein, who in 1959 began to shape a hypothesis that would create an anti-squat (past parallel anyway) “crusade”, which was match with an anti-klein campaign, his study and the (in)validity of his findings.

It’s quite fascinating to see how history has shaped what we do today.

Where the idea of deep squats are bad for your knees began….

In 1961 Karl Klein published a study called “The deep squat exercise as utilized in weight training for athletes and its effects on the ligaments of the knee” in the journal of association for physical and mental rehabilitation.

Dr. Klein, with his device measuring ligament strength.
(The alcalde, university of texas alumni magazine ,1964)

Klein investigated, with the aid of a self-designed measuring device, knee structures in competitive weightlifters that frequently performed deep squats. His findings showed increased laxity in the collateral and anterior cruciate ligament (ACL) compared with a control group (who had done no competitive lifting or no full squatting as part of their training).  

In layman’s terms, he found that deep squats stretched out the ligaments of the knee, potentially compromising stability and increasing the risk of injury significantly.

Klein recommended squatting to parallel, at most.

This study was boosted by many other bodies over the next while, sports illustrated (Underwood J, 1962.) gave this study a major boost when they covered it a year later. This snow balled, the American medical association released a position statement cautioning against deep squats, the United States Marine Corp eliminated the “Squat jumper” from its conditioning regime, the New York school system FORBID full squats in gym class.

Some rebelled against these findings, Dr. John R. Pulskamp (a contributor to Strength & Health, one of the earliest weightlifting, bodybuilding magazines) 1964, “Full squats are not bad for your knees and they should certainly not be omitted out of fear of knee injury. If done properly even limit poundage will not bother a normal knee” (Pulskamp John, 1964). However, Kleins findings and anti-squat recommendations were widespread.

This questioning of Kleins findings is what sparked a great debate for many years. (The beauty of science) The quality of Klein’s study came under scrutiny and the study, with a copy of the device, was even replicated in 1971 by Meyers et al (1971). This study reported no significant differences between those who performed full squats versus the half squat. Did Klein knowingly manipulate his methods/findings in the study….?

More and more studies have failed to find any association between deep squats and injury risk in health subjects (Panariello et al. 1994, Steiner et al. 1986).

Deep squats.

In fact, anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) forces have shown to reduce at higher flexion angles (lower squat). ACL forces peak between 15o and 30o of flexion, decreasing significantly at 60o and even staying consistently low at higher flexion angles (Kanamori et al 2000, Li et al 1999, Sakane et al 1997).

PCL forces peak at approximately 90o and quickly decline beyond that (Li et al. 2004). Beyond 120o PCL forces are minimal. Therefore, the potential for injury is greatly reduced at the deeper portions of the squat.

Squatting at high flexion would only pose a threat do those with existing knee pathology (chondromalacia, osteoarthritis, osteochondritis) and/or those who had surgical intervention (e.g Meniscectomy, PCL reconstruction) (Nagura et al. 2002).

Finally, what’s most important to identify before going “ass to grass” is your technique.

There’s a big scope, to simplify there are 3 points across the range.

  1. Poor technique, inadequate mobility, some red flags in the movement patterns, all of which are exacerbated under increased load. This zone is a no-go and will accumulate to injury over time.
  2. Adequate technique, this is where most of us find ourselves, no red flags but some “power” leaks and inefficient movement patterns. Safe but technique can improve.
  3. Perfect technique, rare to see people in this zone, years of honing a craft, optimising forces across all joints and great movement patterns. We aim to be here.

As always, our aim is to exercise/training SAFELY and efficiently.

“Train with purpose, not habit.”

Side note:

Glute activation increases with more depth during the squat (Caterisano et al 2002), so if you want to build booty then deep squats J

“Hip extensor moments increase with increasing squat depth, so full squats may be beneficial for those seeking to maximize strength of the hip musculature.” (Schoenfeld et al. 2010).


  1. Kanamori A, Woo SL, Ma CB, Zeminski J, Rudy TW, Li G, and Livesay GA. The forces in the anterior cruciate ligament and kneekinematics during a simulated pivot shift test: A human cadaveric study using robotic technology. Arthroscopy 16:633–639, 2000.
  2. Klein K. The deep squat exercise as utilized in weight training for athletes and its effects on the ligaments of the knee. J ssoc phys Ment Rehabil 15: 6–11, 1961.
  3. Li G, Rudy TW, Sakane M, Kanamori A, Ma CB, and Woo SL. The importance of quadriceps and hamstring muscle loading on knee kinematics and in-situ forces in the ACL. J Biomech 32: 395–400, 1999.
  4. Li G, Zayontz S, Most E, DeFrate LE, Suggs JF, and Rubash HE. In situ forces of the anterior and posterior cruciate ligaments in high knee flexion: An in vitro investigation. J Orthop Res 22: 293–297, 2004.
  5. Markolf KL, Slauterbeck JL, Armstrong KL, Shapiro MM, and Finerman GA. Effects of combined knee loadings on posteriorcruciate ligament force generation. J Orthop Res 14: 633–638, 1996.
  6. Meyers E. Effect of selected exercise variables on ligament stability and flexibility of the knee. Res Q 42: 411–422, 1971.
  7. Nagura T, Dyrby CO, Alexander EJ, and Andriacchi TP. Mechanical loads at the knee joint during deep flexion. J Orthop Res 20: 881–886, 2002.
  8. Panariello R, Backus S, and Parker J. The effect of the squat exercise on anteriorposterior knee translation in professional football players. Am J Sports Med 22:768–773, 1994.
  9. Pulskamp, John R M.D, Ask the doctor, strength & health May p82, 1964
  10. Sakane M, Fox RJ, Woo SL, Livesay GA, Li G, and Fu FH. In situ forces in the anterior cruciate ligament and its bundles in response to anterior tibial loads. J Orthop Res 15: 285–293, 1997.
  11. Schoenfeld BJ. Squatting kinematics and kinetics and their application to exercise performance. J Strength Cond Res 24: 3497–3506, 2010
  12. Steiner M, Grana W, Chilag K, and Schelberg-Karnes E. The effect of exercise on anterior-posterior knee laxity. Am J Sports Med 14: 24–29, 1986.
  13. Underwood J. The knee is not for bending, Sports Illustrated 16: 50, 1962.
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