PRO
The squat is one of the most popular exercises for developing lower-body strength, but technically speaking, the squat can be a difficult exercise for many athletes to perform correctly. Coaches should use the cue, “sit back into the squat,” as a way to teach proper squatting technique. The goal of the squat exercise is to increase lower-body strength, which is thought to carry over to athletic performance. At the same time, it should be performed in a way that minimizes injury risk during training. Sitting back into the squat is an effective teaching method to help athletes perform this exercise correctly and achieve those two goals.
Sitting back into the squat, also known as the hip hinge by McGill (6), should be used to initiate the eccentric portion of the lift. Sitting back allows the gluteus maximus-the powerful hip extensors-to immediately become a part of the lift, particularly increasing activation in a deeper squat. Without this posterior shift, the squat exercise will emphasize the quadriceps throughout the lift. Research shows that sitting back and preventing the knees from moving too far beyond the toes does increase hip torque (2).
This same research and more has shown that sitting back to minimize anterior translation of the knees will also decrease torque at the knee joints (2,5). The quadriceps are still a major component of the lift, but now, the glutes can share the load more evenly distributing forces throughout the lower extremities. For those with knee pain, this can make an immediate difference in their ability to perform the lift. For athletes without current knee issues, it can be a way to avoid future problems because of overloading. To achieve a parallel squat or deeper, the knees will travel past the toes to a degree, but it should be clear that “sitting back” is not a way of preventing this but rather limiting excessive anterior shift.
Engaging the glutes by sitting back also has the effect of preventing excessive lumbar lordosis, a common cause of spondylolytic disorders. The gluteus maximus has the ability to resist excessive anterior tilting of the pelvis because it offsets the pull of the lumbar paraspinals, to keep the lumbar spine in a neutral position. It has been suggested that repetitive hyperextension movements (extension of the lumbar spine beyond the anatomical limits) place stress through the pars interarticularis and over time may lead to a spondylolysis (4,7). The ability to maintain a neutral lumbar spine throughout the lift has been shown to increase stability through the spine, allows it to bear greater compressive loads, and reduces shear forces (3).
Another biomechanical advantage of sitting back is to reduce the ankle dorsiflexion moment. In other words, the tibia stays more vertical. As the knees travel past the toes, dorsiflexion requirements become greater. An athlete with “stiff ankles” will do 1 of 3 things: (a) the heels could come off the floor and increase shear forces at the knee (5), (b) the heels come off the floor causing the athlete to lose balance, and (c) excessive subtalar pronation occurs along with femoral internal rotation with the result being unacceptable valgus at the knees. The combination of increased knee valgus and anterior tibial shear forces has also been shown to increase stress on the anterior cruciate ligament (5).
When using the squat exercise to enhance performance, sitting back can be an advantageous teaching tool because of the greater amount of hip extension and contribution from the glute complex. It has been shown that during acceleration, the glutes and quadriceps supply the majority of force during triple extension (1). This could be significant for an athlete exploding out of a 3-point stance or from blocks, as well as those positioned in a “defensive” position who must then accelerate in another direction.
To change direction quickly, an athlete needs to be able to resist the momentum of the center of mass via eccentric contractions of the leg extensor muscles (8). Effective change of direction then requires the athlete to get low with an increased trunk flexion angle to effectively recruit the glutes. In essence, this is sitting back just as taught in the squat.
Teaching athletes to sit back to initiate the squat can have several important benefits, including a more even distribution of load between the hip and knee extensors, maintaining a neutral spine, keeping the heels on the floor, and preventing valgus collapse of the knees. Each of these can lead to a safer and more effective squat during training and potentially lead to greater athletic performance.
Joe Heiler, PT, CSCS
SportsRehabExpert.com, Kingsley, MI.
REFERENCES
1. Cronin J and Hansen KT. Resisted sprint training for the acceleration phase of sprinting.
Strength Cond J 28(4): 42-51, 2006.
2. Fry AC, Smith JC, and Schilling BK. Effects of knee position on hip and knee torque.
J Strength Cond Res 17: 629-633, 2003.
3. Gunning JL, Callaghan JP, and McGill SM. The role of prior loading history and spinal posture on the compressive tolerance and type of failure in the spine using a porcine trauma model.
Clin Biomech 16: 471-480, 2001.
4. Harvey J and Tanner S. Low back pain in young athletes. A practical approach.
Sports Med 12: 394-406, 1991.
5. Markolf KL, Burchfield DM, Shapiro MM, Shepard MF, Finerman GAM, and Slauterbeck JL. Combined knee loading states that generate high anterior cruciate ligament forces.
J Orthop Res 13: 930-935, 1995.
6. McGill S.
Ultimate Back Fitness and Performance (3rd ed). Ontario, Canada: Backfitpro Inc, 2006. pp. 191-193.
7. Nau E, Hanney WJ, and Kolber MJ. Spinal conditioning for athletes with lumbar spondylolysis and spondylolisthesis.
Strength Cond J 30(2): 43-52, 2008.
8. Sheppard JM and Young WB. Agility literature review: Classification, training, and testing.
J Sports Sci 24: 919-932, 2006.
CON
The barbell squat is an important core exercise for multijoint strength training of the lower extremity. Executed properly, this exercise challenges the ankle, knee, hip, and back extensor muscle groups. Knowledgeable coaches and strength professionals recognize the importance of proper technique to both performance and injury prevention. Unfortunately, many definitions of “proper technique” exist, and accepted criteria are not always mutually compatible. This can lead to misconceptions that undermine effective training and risk athletes' health.
One of the most common instructions given to athletes performing the squat is to “sit back” during the descending phase of the movement. This is often measured by the position of the knee joint compared with that of the toe. According to many practitioners and National Strength and Conditioning Association guidelines, the knee should not travel anterior to the toe (1). Two reasons are usually cited: (a) an emphasis on loading the hip extensor muscles and (b) protection of the knee joint from excess flexion. While “sitting back” may be effective for some athletes, it has important drawbacks to consider. Furthermore, neither goal requires the athlete to make a purposeful effort to “sit back”, and there are advantages in not doing so.
“Sitting back” places the hip joint further behind the feet. Because this moves the body's center of mass posteriorly, maintaining weight over the feet requires some form of compensation to prevent falling backward. This is usually accomplished by anterior lean of the trunk, ideally from increased hip flexion while maintaining a neutral spine. However, this requires adequate hip range of motion (ROM) as well as back extensor strength and spinal stability. Otherwise, an athlete must flex the spine to maintain balance, presenting well-documented risks that contradict accepted squatting guidelines (1,6). A study by Fry et al. (4) showed that restricted anterior movement of the knees during squatting increased loads at the hip but also caused excessive forward lean of the trunk and was likely to inappropriately transfer load to the lower back. Although reduced knee flexion is proposed to decrease stress in the knee, it may also compound risk to the spine by limiting hip ROM afforded by the 2-joint hamstring muscles. Thus, in an attempt to protect the knee, “sitting back” may pose additional risk to the spine. Further, recent evidence suggests that excess flexion can aggravate hip joint pathology (e.g., acetabular impingement and/or labral tears) in some athletes (5).
The major determinant of lower extremity joint loads during the squat is the location of the ground reaction force (GRF). Especially with higher barbell loads, GRF location is driven primarily by the position of the upper body because it has the greatest mass. Whether one “sits back” or not, forward lean of the trunk and/or greater barbell mass places greater relative demand on the hip joint (3,4). The difference is that “sitting back” requires this forward lean to maintain stability. If instead the knees are allowed to remain at or even beyond the toes, a greater range of trunk positions is possible. Forward lean can be allowed if hip ROM and back strength permit. Alternatively, a more erect position can be maintained while still keeping weight over the feet. Shifting weight forward has the added benefit of increasing torque at the ankle joint, providing greater training stimulus to the plantar flexors (3).
A more anterior knee position usually implies greater ankle dorsiflexion and knee flexion, which are often said to pose a risk to the knee. Evidence to date however suggests that thigh-parallel squats are safe for healthy athletes, although deeper squatting might pose additional risk to the knee menisci or ligaments (principally the posterior cruciate ligament) (2). In the presence of a knee injury, reduced barbell loads and/or limited squat depth to control knee flexion are better options than a strategy that could pose undue risk to the spine.
It should be noted that many athletes have restrictions in dorsiflexion ROM that compel them to “sit back,” causing similar concerns. Corrective measures could include mobility/flexibility training, limitation of squat depth, changes in barbell load, and/or use of shims under the heels. In general, differences among individual athletes, for example, limb length, may require different positioning. “Knees behind the toes” is likely not an appropriate strategy for everyone.
Finally, rejecting a “sit back” approach should not be interpreted as endorsing a “kneel forward” one. Excessive anterior movement of the knees may shift weight too far forward onto the toes, again producing instability. Correct squatting technique should emphasize (a) a stable platform with weight evenly supported underfoot, (b) a neutral spine, and (c) knee, hip, and ankle ROM within safe/tolerated ranges. Variations in joint loading may be accomplished by changing trunk position, barbell load, and/or squat depth-as acceptable within these criteria-depending upon an individual athlete's strengths, weaknesses, and training goals.
Shawn C. Sorenson, MS, CSCS
University of Southern California, Los Angeles, CA.
REFERENCES
1. Earle RW and Baechle TR. Essentials of Strength Training and Conditioning. Champaign, IL: Human Kinetics, 2008. pp. 350-351.
2. Escamilla RF. Knee biomechanics of the dynamic squat exercise. Med Sci Sports Exerc 33: 127-141, 2001.
3. Flanagan SP and Salem GJ. Lower extremity joint kinetic responses to external resistance variations. J Appl Biomech 24: 58-68, 2008.
4. Fry AC, Smith JC, and Schilling BK. Effect of knee position on hip and knee torques during the barbell squat. J Strength Cond Res 17: 629-633, 2003.
5. Lewis CL and Sahrmann SA. Acetabular labral tears. Phys Ther 86: 110-121, 2006.
6. McGill S. Low Back Disorders: Evidence-Based Prevention and Rehabilitation. Champaign, IL: Human Kinetics, 2002. pp. 118-124.
;)
Table: No Caption Available
