Geschatte leestijd: 6 minutenFitness instructors often explain exercises to their clients with one priority in mind: Safety. The last thing they want is for their client to have a heart attack while running and be launched off the treadmill or crushed under a barbell. After all, that costs clients. Therefore, common injuries and limited mobility of people who don’t move much are often taken into account.
For example, with bench pressing, it is first explained that the arms should lower until the elbows are parallel to the torso and no further. This is due to possible limited mobility of the shoulder joint. However, in practice, this means you’re only doing half of the chest exercise. Using a barbell would mean it stays about 10-15 centimeters above the chest instead of lowering further to touch it for a full Range of Motion (ROM). Once the client is accustomed to the exercise and the instructor sees that the mobility of the shoulder joint is sufficient, it will be adjusted to the correct, full execution.
Squatting: “How deep can you go?”
However, with squats, it seems that this later improvement is never made, and many people continue to do a limited, almost half, squat on the advice of fitness instructors and trainers because it’s considered safer. An adjustment for beginners and people with limitations then suddenly becomes the standard. “Don’t let your knees go past your toes!” you hear.
This is like people telling Lance Armstrong at the start of the Tour, “Be sure to attach your training wheels, Lance, or you’ll fall!” (the one thing he never thought he’d need).
This article aims to explain why it’s actually recommended to fully execute the squat and therefore squat deeper.
Knees past the toes during the squat
Anatomically, the tip about not letting the knees go past the toes is incorrect considering the differences between individuals. Despite jokes from opponents like, “Try running or climbing stairs without your knees going past your toes,” these are a bit silly considering the instruction is specifically about squatting and not running or stair climbing. It’s meant as a tool to ensure a generous angle in the knee.
When standing, the knee forms an “angle” of almost 180 degrees, with the thigh bone straight above the lower leg. As you start bending by pushing your butt backward and down, you reach a point where the angle is 90 degrees. To go beyond this point and thus squat deeper, many people need to tilt their lower legs forward from the ankles to maintain balance and prevent falling backward. This often causes the knees, but not for everyone, to go past the toes. Therefore, the tip not to let the knees go past the toes is mainly intended to prevent the knee angle from becoming smaller than 90 degrees.
More pressure on the knees or more pressure on the lower back?
Squatting is a compound leg exercise involving multiple muscle groups. Besides the quadriceps, for example, the hamstrings and lower back are also engaged. Especially, the ratio between the load on the quadriceps and the load on the lower back is important here. The modified, restricted squat may indeed result in slightly less stress on the knees but adds extra movement and stress to the lower back (1,2). The additional stress this imposes on the lower back and spine is much greater than the stress saved on the knees (2).
“However, in order to optimize the forces at all involved joints, it may be advantageous to permit the knees to move slightly past the toes when in a parallel squat position.”
A.C. Fry, University of Memphis
Researchers from the University of Memphis measured in 2003 the pressure on the knee and hip joints during restricted or unrestricted squats. They found that when doing unrestricted squats (knees past toes), the pressure on the knees increased by almost 28%.
“See!,” I hear your fitness instructor shout.
However, looking at the alternative, we see that the pressure on the hip joint increases by over 973%! Researchers attribute this to the fact that with restricted squats, the torso must lean further forward to prevent falling backward.
So the question is whether you consider this a good deal: Almost 30% less pressure on the knees at the expense of almost 1000% more pressure on the hip joint, ultimately transferred to the lower back and spine? Apart from the difference in percentages, the importance of the various body parts (think of the nerve pathways in the spinal cord) should already give you the answer.
Squatting and knee ligaments
During squatting, pressure is placed on the knee ligaments and the patellar tendon. The knee ligaments ensure that the thigh bone stays directly above the lower leg and doesn’t shift forward or backward. The patellar tendon is the attachment of the quadriceps to the lower leg. It runs over the kneecap and allows the leg to be extended.
In their research report, the University of Memphis researchers refer to various studies showing that the forces on these ligaments are well within their maximum capacity during squats.
Speed of the squat
It’s also important to consider that the pressure on these ligaments increases when the movement is made faster (3). For example, many would do well to squat down slower. The most common mistake I see people make in strength training in general is that they perform the eccentric part of the exercise too quickly. In squatting, this is the part where you lower. This is often done too quickly because it saves energy that can be used to come back up. As a result, more weight can be lifted, and people think they’ll make more of an impression in the gym.
Fortunately, most people don’t realize that the elasticity of the attachments (in this case, the patellar tendon and attachments of the lower back) also makes it easier to lift the weight when the descent is performed faster. If you’re a weightlifter or powerlifter trying to lift as much weight as possible, that’s fine. However, if you’re training to increase your strength and/or muscle mass, the goal is to make it hard for the muscles.
Lowering slowly reduces the pressure on the knees while increasing the load on the muscles. Moreover, by descending slowly, you train the eccentric part better, and that part leads to more muscle growth than the concentric part (rising in squats)(4). So, it’s a win-win-win situation. Try to lower in at least three seconds instead of dropping down.
Position of the barbell during the squat
Finally, the position of the barbell is also important. You can influence the pressure on the knees and lower back by holding it higher in the neck like weightlifters do or lower on the shoulder blades like powerlifters (5,6).
Because the torso is
bent forward during squatting, a higher placement of the barbell also means it’s further forward. This moves the center of balance forward, allowing for deeper squats without having to bend forward more from the hips to prevent falling backward. This results in slightly higher knee stress while significantly reducing lower back stress.
If you place the bar lower on the back, you bring the weight backward, requiring you to lean further forward from the hips to maintain balance. This greatly increases the pressure on the spine and lower back. The pressure on the knees then becomes slightly lower because they are less bent.
Conclusion
Unless you have a knee injury that justifies disproportionately loading the lower back compared to the knees, there’s no reason to keep the angle in the knees large. The tip that ensures this, “Don’t let your knees go past your toes,” was originally intended as a safe method for people who have no experience with the movement. Even in this respect, however, you should consider how safe this is given the greater stress it means for the lower back.
Research shows that the pressure on the knee ligaments and patellar tendon during squats is well within their maximum capacity.
In addition to the position of the knees relative to the toes, you also influence the pressure on the knees with the speed of execution of the squat. Lower slowly, in about three seconds, to not increase the pressure and at the same time develop more muscle mass.
Finally, you also influence the pressure on the knees and lower back with the position of the barbell. Holding it higher, in the neck, slightly increases knee stress and greatly reduces lower back stress.
If you have bad knees and a bad back, leave the barbell squat alone and go for the squat in the Smith Machine. With the Smith Machine, the bar is fixed in the rack and can only move up and down. Because you can lean against the bar with this device, you can keep your back straight and maintain a large angle in the knees without falling backward.
References
- List R, Gülay T, Stoop M, Lorenzetti S. Kinematics of the trunk and the lower extremities during restricted and unrestricted squats. J Strength Cond Res. 2013 Jun;27(6):1529-38. doi: 10.1519/JSC.0b013e3182736034.
- Fry, AC., Smith, JC, S., & Schilling, BK. (2003, November). Effect of knee position on hip and knee torques during the barbell squat. Journal Of Strength And Conditioning Research / National Strength & Conditioning Association, 17(4), 629-633.
- ANDREWS, J.G., J.G. HAYS, AND C.L. VAUGHAN. Knee shear forces during a squat exercise using a barbell and a weight machine. In: Biomechanics (Vol. 8B). H. Matsui and K. Kobayashi, eds. Champaign, IL: Human Kinetics, 1983. pp. 923–927.
- Enoka, R. M. Neural adaptations with chronic physical activity. J. Biomechanics 30:447-455, 1997.
- FRY, A.C., T.A. ARO, J.A. BAUER, AND W.J. KRAEMER. A comparisonof methods for determining kinematic properties of three barbell squat exercises. J. Hum. Move. Stud. 24:83–95. 1993.
6. WRETENBERG, P., Y. FEND, AND U.P. ARBORELIUS. High- and low-bar squatting techniques during weight-training. Med. Sci.Sports Exerc. 28:218–224. 1996.
