Article Summary: The Biomechanics of Squat Depth by Brad Schoenfeld

This article discusses the idea that deep squats may increase knee ligament laxity. One study by Klein using weightlifters who regularly perform deep squats, found an increased laxity in the ACL, MCL and LCL knee ligaments compared to a control group (1,2). However, Klein’s study was performed in 1961 and Shoenfeld points out that there are more recent studies which disprove this theory (3,4,5) as well as evidence to demonstrate the opposite is true (6). A group of male power lifters were found to have tighter anterior drawer (ACL) tests than the control group (6). It would be interesting to see how these figures compare to a group of female power lifters, seeing that female athletes have higher rates of ACL rupture than male athletes.

The highest forces on the ACL occur at 15-30 degrees of knee flexion, with the lowest forces occurring at 60 degrees knee flexion and greater (7,8,9). Therefore, deep squats would not subject the ACL to high shear forces (1). Another benefit of deep squatting is that on EMG, the gluteus maximus muscle activity was found to be greater in a full squat compared to a quarter squat or squat to parallel (2). This is key since:

1. Gluteus maximus is a primary hip extensor (contributing to force production during running and jumping)
2. Gluteus maximus is a muscle which is commonly underdeveloped, as in those with lower crossed syndrome.

Therefore, deep squatting is not contraindicated in people with healthy knees, as it has not been shown to increase knee ligament laxity (1,3,4,5,6). Full squats increase muscle activity in the gluteus maximus (1,2) and should be considered as a useful tool in athletic development. Choosing optimal squat depths in an athlete’s program should take into account many factors such as the athlete’s sport, training goals, and injury history (1).

1. The Biomechanics of Squat Depth, NSCA Hot Topic Series, Brad Schoenfeld.
2. Klein K. The deep squat exercise as utilized in weight training for athletes and its effects on the ligaments of the knee. JAPMR. 15(1):6 – 11.1961.
3. Meyers E. Effect of selected exercise variables on ligament stability and flexibility of the knee. Research Quarterly. 42(4):411 – 422. 1971.
4. Panariello R, Backus S, Parker J. The effect of the squat exercise on anterior-posterior knee translation in professional football players. American Journal of Sports Medicine. 22(6):768 – 773. 1994.
5. Steiner M, Grana W, Chilag K, and Schelberg-Karnes E. The effect of exercise on anterior-posterior knee laxity. American Journal of Sports Medicine.14 (1):24 – 29. 1986.
6. Escamilla RF, Fleisig GS, Zheng N, Lander JE, Barrentine SW, Andrews JR, Bergemann BW, and Moorman CT. Effects of technique variations on knee biomechanics during the squat and leg press. Medicine and Science in Sports and Exercise. 33:1,552 – 1,566. 2001.
7. Kanamori A, Woo SL, Ma CB, Zeminski J, Rudy TW, Li G, and Livesay GA. The forces in the anterior cruciate ligament and knee kinematics during a simulated pivot shift test: A human cadaveric study using robotic technology. Arthroscopy. 16(6):633 – 639. 2000.
8. Li G, Rudy TW, Sakane M, Kanamori A, Ma CB, and Woo SL. The importance of quadriceps and hamstring muscleloading on knee kinematics and in-situ forces in the ACL. Journal of Biomechanics. 32(4):395 – 400. 1999.
9. Signorile JF, Weber B, Roll B, Caruso J, Lowensteyn I, and Perry AC. An electromyographical comparison of the squat and knee extension exercises.Journal of Strength and Conditioning Research. 8:178 – 183. 1994.

Karlos wrote:Trouble is, many people squat deep who shouldn't. Deep squatting requires a surprising amount of flexability. I suffered back and knee pain/injury due to deep squatting with poor hip mobility. ie. pelvic tuck & torque stress on knees.

health4ni wrote:^^ I think in an ideal world then doing at least 30mins warmup with smr, mobility, activation etc exercises is great. And as an athelete I'd say it's a priority. But for working people with limited time that's too much. A smart 10min warmup and then some smr, mobility etc on non-training days is the way to go for most people.

health4ni wrote:Try these for starters:
http://www.dieselcrew.com/essential-hip-mobility-how-to-warm-up-correctly-2
http://www.dieselcrew.com/lower-back-rehab-fix-lower-back-injuries

Karlos wrote: That's true, but the benefits are so vast in doing it prior to lifting that to anyone who can spare an extra 30 mins, it's well worth it imo. Especially before squats.