There has been much debate on proper squat techniques. Is it proper to maintain a vertical shin and prevent the knees from going beyond the toes? Is it better to squat and allow the knee to go beyond the toes? Proponents of the vertical shin technique argue it is best to save the knees and this helps increase posterior chain strength. Whereas proponents of parallel lines say, distribute the weight evenly and save the back. The purpose of this blog is to shed some light on the debate and provide the rationale for proper squat technique.
Early studies state that squatting with external loads causes undue stress and damage to soft tissue at the knee joint. This precipitated many experts to change squat mechanics. A vertical shin angle prevents excessive knee flexion, thus limiting the stress placed at the knee joint and potential damage to integral knee structures such as the meniscii, articular cartilage and ligaments. In addition, many state that maintaining a vertical shin angle allows for enhanced strengthening of the posterior chain (hamstrings, glutes, low back).
I agree it is important to protect the knees. However, the lower back is much more important, in my opinion. Low-back pain is one of the major forms of musculoskeletal degeneration seen in the adult population, affecting nearly 80% of all adults (1). It has been estimated that the annual costs attributable to low-back pain in the United States are greater than $26 billion (2). In addition, 6 to 15% of athletes experience low-back pain in a given year (3, 4). The body is an interconnected chain, and compensation or dysfunction in the LPHC region can lead to dysfunctions in other areas of the body (5). So why do we squat to protect the knees? How should we squat?
Proper squat mechanics requires optimal flexibility at the ankle, knees, and hips during the descent of the squat. When these joints are moving together, forces will be disturbed optimally and equally throughout the kinetic chain. If one of the joints has limited ability to move, another joint must compensate to make up for the lost movement. For example, if you are trying to pick something off of the floor and do not bend your knees you must bend at the back. Using this example, if we squat like this (limiting knee flexion or ankle dorsiflexion) we are asking the lower back to lift weight in a biomechanically disadvantaged position. You know the phrase “lift with your legs not your back.”
Do a quick check and test your squat mechanics. Evaluate your technique by watching in a mirror. At the bottom of the squat the torso and tibia should be parallel to each other (See image below). Have you ever noticed how a baby squats? Do a quick google search for baby squat. You will be amazed at their technique. They lift properly, because they have the flexibility to get in to a deep squat without excessive leaning at the low back. It does not matter if the knees go past the toes. The most important thing to ask: is the back parallel with the shin?
Fry et al. (2003) examined the hip and knee torque forces of variations of parallel squats and concluded appropriate joint loading during this exercise may require the knees to move slightly past the toes. Restricting squats created significant increases of excessive forward lean and subsequent increased torque loads at the low back and hip (6). Maintaining a vertical shank did not yield change knee torque significantly (6).
Torque is a measure of rotational force about an axis of rotation. Simply put torque is a product of force and lever length from the axis of rotation to point of force of application (Τ = r x F) where Τ is linear torque, r is the displacement vector and F is force. Look at the two images below and notice the Torque values at the knee and low back:
Squatting with a Vertical Shin
Squatting with vertical shin:
αlb= 78° αk= 102° F = 135lbs (600.5 Newtons)
B to C= 19 inches (.48 meters). A to B = 2.75 inches (0.07 meters). A to C = 16.25 inches (0.41meters)
Linear Torque Low Back:
Τlb = r x F
Τlb = 0.41m x (600.5N)
Τlb = 246.2 N·m
Linear Torque at the Knee:
Τk = r x F
Τk = 0.07m x (600.5N)
Τk = 42.04 N·m
Squatting with parallel lines
αlb= 90° αk= 90° F = 135lbs (600.5 Newtons)
B to C= 19 inches (0.48 meters) A to B = 9.5 inches (0.24 meters) A to C = 9.5 inches (0.24 meters)
Linear Torque Low back:
Τlb = r x F
Τlb = 0.24m x (600.5N)
Τlb = 144.12 N·mLinear Torque Knee:
Τk = r x F
Τk = 0.24m x (600.5N)
Τk = 144.12 N·m
You can clearly see that squatting with a vertical shin reduces stress placed on the knee, but significantly increases torque on the low back. Do we really want to place an increased load at the lower back, when it is so prone to injury? The most important thing to consider is overall exercise technique. Lifting with ideal posture is paramount for injury prevention. When this occurs forces will be distributed equally throughout the kinetic chain.
1. Walker BF, Muller R, Grant WD. Low back pain in Australian adults: prevalence and associated disability. J Manipulative Physiol Ther 2004;27:238–44
2. Luo X, Pietrobon R, Sun SX, Liu GG, Hey L. Estimates and patterns of direct health care expenditures among individuals with back pain in the United States. Spine 2004;29:79–86.
3. Nadler SF, Malanga GA, DePrince M, Stitik TP, Feinberg JH. The relationship between lower extremity injury, low back pain, and hip muscle strength in male and female collegiate athletes. Clin J Sport Med 2000;10:89–97.
4. Nadler SF, Malanga GA, Feinberg JH, Rubanni M, Moley P, Foye P. Functional performance deficits in athletes with previous lower extremity injury. Clin J Sport Med 2002;12:73–8.
5. Powers CM. The influence of altered lower-extremity kinematics on patellofemoral joint dysfunction: a theoretical perspective. J Orthop Sports Phys Ther 2003;33(11):639–46.
6. Fry, A.C., J.C. Smith, and B.K. Schilling. Effect of knee position on hip and knee torques during the barbell squat. J. Strength Cond. Res. 17(4):629–633. 2003