Squatting depth

tim290280 · Sep 24, 2008

The problem with squatting depth is that there are a number of things happening to the joint and they can vary depending on how the squat is performed. As long as the knees and hips rise as one and the weight is not shifted forward (or sideways) onto the toes then you have a decent squat that will keep the knee within acceptable force parameters.

There are few things to consider with squatting depth: shear forces on the ligaments and tendons, compressive forces on the knee cartilages, relative loading, and excessive depth. Excessive depth is easy; go too deep and your hamstrings and calves meet and begin to lever the knee apart, not good! Relative loading is also reasonably simple; you can squat more weight through a shorter ROM and will put greater stressors on the knee than is typically measured in studies.

Meniscus starts to get damaged at 25MPa. Squatting with bodyweight is 4-5MPa, walking can get as high as 14MPa (wonder what running does?!)

Tibiofemoral Joint Contact Force in Deep Knee
Flexion and Its Consideration in Knee Osteoarthritis
and Joint Replacement
Takeo Nagura,1 Hideo Matsumoto,1 Yoshimori Kiriyama,1 Ajit Chaudhari,2 and Thomas P. Andriacchi2
The aim of the study was to estimate the tibiofemoral joint force in deep flexion to consider how the mechanical load affects the knee. We hypothesize that the joint force should not become sufficiently large to damage the joint under normal contact area, but should become deleterious to the joint under the limited contact area. Sixteen healthy knees were analyzed using a motion capture system, a force plate, a surface electromyography, and a knee model, and then tibiofemoral joint contact forces were calculated. Also, a contact stress simulation using the contact areas from the literature was performed. The peak joint contact forces (M ± SD) were 4566 ± 1932 N at 140 degrees in rising from full squat and 4479 ± 1478 N at 90 degrees in rising from kneeling. Under normal contact area, the tibiofemoral contact stresses in deep flexion were less than 5 MPa and did not exceed the stress to damage the cartilage. The contact stress simulation suggests that knee prosthesis having the contact area smaller than 200 mm2 may be problematic since the contact stress in deep flexion would become larger than 21 MPa, and it would lead damage or wear of the polyethylene.

Contact stresses in the knee joint in deep flexion
Ashvin Thambyah, James C.H. Goh∗, Shamal Das De
Department of Orthopaedic Surgery, National University of Singapore, Singapore 119074, Singapore
Received 25 August 2004; accepted 2 September 2004
Abstract
The contact stresses in the knee that arise from activities involving deep flexion have not been given due consideration in view of social and cultural practice amongst many Asians that frequently cause the engagement of these activities. Excessively large stresses (>25MPa) can cause cartilage damage and may be the precursor to the development of degenerative disease of the joint. In this study, forces in the knee derived from previous studies of human walking and squatting were applied to five cadaver knees that underwent quasi-static mechanical testing. This was conducted using a materials-testing machine and a custom-made apparatus that allowed secure and consistent loading of the knee specimen in flexion beyond 120◦. A thin-film electronic pressure transducer was inserted into the cadaver tibiofemoral joint space to measure force and area. Throughout the various positions simulating specific phases of walking, it was found that stresses peaked to 14MPa (standard deviation was 2.5MPa). In deep flexion, the peak stresses were significantly larger by over 80%, reaching the damage limits of cartilage. The results from this biomechanical study suggest that the adequacy of articular cartilage to support loads in the knee joint during deep flexion may be questionable.

Patellofemoral joint kinetics during squatting in collegiate women athletes
George J. Salem, and Christopher M. Powers
Objective. To characterize the biomechanics of the patellofemoral joint during squatting in collegiate women athletes.
Design. Repeated measures experimental design.
Background. Although squatting exercises are required components of most intercollegiate resistance-training programs and are commonly performed during rehabilitation, the effects of various squatting depths on patellofemoral joint stress have not been quantified.
Methods. Anthropometric data, three-dimensional knee kinematics, and ground reaction forces were used to calculate the knee extensor moment (inverse dynamics approach) in five intercollegiate female athletes during squatting exercise at three different depths (approximately 70°, 90° and 110° of knee flexion). A biomechanical model of the patellofemoral joint was used to quantify the patellofemoral joint reaction force and patellofemoral joint stress during each trial.
Results. Peak knee extensor moment, patellofemoral joint reaction force and patellofemoral joint stress did not vary significantly between the three squatting trials.
Conclusions. Squatting from 70° to 110° of knee flexion had little effect on patellofemoral joint kinetics. The relative constancy of the patellofemoral joint reaction force and joint stress appeared to be related to a consistent knee extensor moment produced across the three squatting depths.
Relevance
The results of this study do not support the premise that squatting to 110° places greater stress on the patellofemoral joint than squatting to 70°. These findings may have implications with respect to the safe design of athletic training regimens and rehabilitation programs.

So if walking and running are higher knee compressive forces than those in the parallel and ass to grass squat with bodyweight then squatting with good form and progressive overload techniques shouldn’t be harmful to the meniscus (within reason). Of course extra weight is going to impact upon these forces greatly. Where the forces get big is when you add weight, and it is much easier to add big weights to shallower depths of squatting. You also tend to have slower “hypertrophy” of the tendons, ligaments and cartilage than in muscles which further exacerbates the issue of adding big weights.

Next post will be on the ligament forces.

Tunen · Sep 24, 2008

But there's a big difference between running/walking and squatting with stable feet. When squatting, there's no impact between the foot and the ground. As far as I know, the impact factor has a great impact (pun intended) on MPa. IMO this makes it really hard to compare MPa's...

tim290280 · Sep 24, 2008

Tunen said:
But there's a big difference between running/walking and squatting with stable feet. When squatting, there's no impact between the foot and the ground. As far as I know, the impact factor has a great impact (pun intended) on MPa. IMO this makes it really hard to compare MPa's...

Yes that is what I was alluding to. :tiphat:

We do activities everyday that have more force on the knee than deep squatting does. So when we see that a squat to 140-155 degree knee bend is 4-5 times less than what is needed to damage the meniscus and walking is 3 times BW squats you don't need to worry about depth damaging the meniscus.

Minchinator · Sep 25, 2008

Interesting stuff, thanks

ibanezman1988 · Nov 29, 2008

i used to do "regular" depth squats and was forced to use a lot of weight.

this ended up really messing up my tendons.

until my dad told me to strip some weight off and do a full range of motion.
i was very skeptical see as i have read countless mumbo jumbo about that being bad for the knees.

well, i put a 5lbs plate under my heel just because i can achieve greater depth that way without feeling pain in my lower back.

i did a full range of motion, and worked out that way for a couple of months. lo and behold, knee pain was gone and i was squating that way ever since.

when you go half way, you're using more weight and you are damaging your tendons by stopping the weight half way. when you stop 400lbs half way, most of the stress is placed on the knee.
however, if you go almost all the way down, now it's more of the glutes and hamstrings that are getting worked and less stress is placed on the knee.

think about it. when your knees hurt when you squat heavy, when does it hurt most?
just as you're about to go back up right?

tim290280 · Nov 29, 2008

ibanezman1988 said:
i used to do "regular" depth squats and was forced to use a lot of weight.

this ended up really messing up my tendons.

until my dad told me to strip some weight off and do a full range of motion.
i was very skeptical see as i have read countless mumbo jumbo about that being bad for the knees.

well, i put a 5lbs plate under my heel just because i can achieve greater depth that way without feeling pain in my lower back.

i did a full range of motion, and worked out that way for a couple of months. lo and behold, knee pain was gone and i was squating that way ever since.

when you go half way, you're using more weight and you are damaging your tendons by stopping the weight half way. when you stop 400lbs half way, most of the stress is placed on the knee.
however, if you go almost all the way down, now it's more of the glutes and hamstrings that are getting worked and less stress is placed on the knee.

think about it. when your knees hurt when you squat heavy, when does it hurt most?
just as you're about to go back up right?

Few points:
Squatting with a plate under the heels is a way of saying that you haven't got the mobility to squat correctly. Fix your mobility.

"Half way down" I assume to mean 90 degrees. This is where knees are most vunerable as the cocontraction of the muscles allows for shear that it offsets at other angles. Stopping at the point and changing direction allows forces to be directly placed onto ligaments and meniscus in a shearing action.

Knees shouldn't hurt from squatting. If a rep hurts you are doing something wrong.

ibanezman1988 · Nov 29, 2008

whoa bud

all olympic weightlifter use special shoes with heals on them for squatting. your body's natural reaction when squatting deep is to lift the heels.

and no, a 90 degree squat is fine. but when you tell someone to go down 90 degrees, they never do. 90 degrees is almost all the way down so they end up doing more of a quarter squat.

all i was saying was that doing a full range of motion is the way to go.

it works for me, my knees don't bother me, and my legs have grown best this way.

why should there be more argument? i'm happy with the way it worked for me. the goal of squatting is to get big legs and i have achieved that without damaging anything.

your article is very informative!

tim290280 · Nov 29, 2008

ibanezman1988 said:
whoa bud

all olympic weightlifter use special shoes with heals on them for squatting. your body's natural reaction when squatting deep is to lift the heels.

If you are going to make a statement at least know the history:
They don't have that much of a heel, it is actually an 1.25-1.5", pretty similar to most running shoes or boots that are worn every day. The difference comes in the solid heel. Putting a plate under your heels is a completely different practice. Read the article, lifters initially went for a big heel of >2.5" but it was gotten rid of as it was only making up for a lack of mobility.

and no, a 90 degree squat is fine. but when you tell someone to go down 90 degrees, they never do. 90 degrees is almost all the way down so they end up doing more of a quarter squat.

90 degree knee bend (unless your shins are completely vertical) is akin to a deep 1/4 squat. Parrallel squats are actually ~100 to 110 degrees. Big difference. I'm sure that I posted the study on knee forces once past 90 degrees (either in this thread or in the articles section), so I think you don't understand what is actually being said.

It is worth noting that the powerlifting style squat of sitting back with vertical shins is only possible with a very wide stance. This is a completely different style of lifting to what was discussed.

all i was saying was that doing a full range of motion is the way to go.

it works for me, my knees don't bother me, and my legs have grown best this way.

Agreed.

why should there be more argument? i'm happy with the way it worked for me. the goal of squatting is to get big legs and i have achieved that without damaging anything.

your article is very informative!

There should be more argument when you make statements about changing the biomechanics of the squat. And don't assume that people only squat to get big legs. Squatting is an important exercise to many sports where they don't need or want big legs. Many people squat purely for strength and performance enhancement. I'm glad you liked the article, it took me a while to compile in any logical sequence. But read it carefully and have a read of the full references quoted.

The Creator · Nov 30, 2008

You make some good points 12 ibanezman1988 about squatting with full range of motion and it is good to hear that it doesnt make knee pain any worse. As far as squatting with a plate under your heel, this shortens your gastrocnemius and this is what allows you to squat lower. That being said, it is not a good practice for squatting movements. Reason being, a gastrocnemius with good flexibility should be able to allow the feet to remain on the ground while squatting low without excess forward lean of the trunk. You should be able to squat hams to calves with 1) your feet flat on the floor and 2) your spine lining up parallel with your tibia (shins). You mentioned back pain associated with keeping your feet flat. This pain is not normal. Many of my clients are surprised to find out that tight gastrocs can lead to problems all the way up in the back. I would suggest you look over my "foam rolling for a better physique" thread for good ideas on how to loosen up those gastrocs.
Nobody is trying to start an argument here. Tim is a smart guy and I think he is just trying to clear up some confusion about the often discussed squat :xyxthumbs:

Daniel Andersson · Nov 30, 2008

IMO parrallel squats work your outer quad more then a "full range" squat.
A "full range" squat feels more in the middle quad and my hamstring. So a deep squat will give you more mass (atleast me) but they will also putt WHAY more stress on your knees whether you feel it or not, hence I only do deep squats up to 120kg [265lbs] and then Parrallel squat the rest of my sets which makes it feel more "comfortable"

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tim290280 · Nov 30, 2008

Creator said:
You make some good points 12 ibanezman1988 about squatting with full range of motion and it is good to hear that it doesnt make knee pain any worse. As far as squatting with a plate under your heel, this shortens your gastrocnemius and this is what allows you to squat lower. That being said, it is not a good practice for squatting movements. Reason being, a gastrocnemius with good flexibility should be able to allow the feet to remain on the ground while squatting low without excess forward lean of the trunk. You should be able to squat hams to calves with 1) your feet flat on the floor and 2) your spine lining up parallel with your tibia (shins). You mentioned back pain associated with keeping your feet flat. This pain is not normal. Many of my clients are surprised to find out that tight gastrocs can lead to problems all the way up in the back. I would suggest you look over my "foam rolling for a better physique" thread for good ideas on how to loosen up those gastrocs.
Nobody is trying to start an argument here. Tim is a smart guy and I think he is just trying to clear up some confusion about the often discussed squat

Good points. Mobility issues often need something more than just stretching.

I regard to the whole heels rising and plate under the heels thing:
I measured my running shoes and my plates. The smallest of my plates is 3/4" thick, the thickest is 2", the most likely plate to be used for the practice is 1.5" thick. The heel on my running shoe was 1.5", while the fore-sole was 1".

So some basic maths later you can see that the sort of shoe that most guys wear at the gym is roughly equivilent to the modern weightlifting shoe, albeit with a harder sole that will maintain the heights measured. Unless you remove the shoe to squat the plate under your heels will actually take you up to 3" heel raise over a 1" fore-foot position. This is not even in the same ballpark as even the most extreme weightlifting shoes (which are no longer made because of the limitations of mobility created).

Hopefully this will get people to stop people squatting with plates under their heels, get them to improve their mobility and into Creator's foam rolling thread,

Hypocrisy86 · Nov 30, 2008

lmao, i thought the title said "squatting death"

damn..

PrinceVegeta · Nov 30, 2008

Nice article tim and nice discussion going on here

All this applies to back squats mostly...so what about front squat? seeing that the heavy load is placed at the front of the body instead of the back which puts more strain in the inner thighs quads and knee's

Any thoughts?

tim290280 · Nov 30, 2008

Daniel Andersson said:
IMO parrallel squats work your outer quad more then a "full range" squat.
A "full range" squat feels more in the middle quad and my hamstring. So a deep squat will give you more mass (atleast me) but they will also putt WHAY more stress on your knees whether you feel it or not, hence I only do deep squats up to 120kg [265lbs] and then Parrallel squat the rest of my sets which makes it feel more "comfortable"

While the various muscles involved in the squat do change their involvement over the ROM the only real change is in the glutes involvement:

J Strength Cond Res. 2002 Aug;16(3):428-32.Links
The effect of back squat depth on the EMG activity of 4 superficial hip and thigh muscles.
Caterisano A, Moss RF, Pellinger TK, Woodruff K, Lewis VC, Booth W, Khadra T.

The purpose of this study was to measure the relative contributions of 4 hip and thigh muscles while performing squats at 3 depths. Ten experienced lifters performed randomized trials of squats at partial, parallel, and full depths, using 100-125% of body weight as resistance. Electromyographic (EMG) surface electrodes were placed on the vastus medialis (VMO), the vastus lateralis, (VL), the biceps femoris (BF), and the gluteus maximus (GM). EMG data were quantified by integration and expressed as a percentage of the total electrical activity of the 4 muscles. Analysis of variance (ANOVA) and Tukey post hoc tests indicated a significant difference (p < 0.001*, p = 0.056**) in the relative contribution of the GM during the concentric phases among the partial- (16.9%*), parallel- (28.0%**), and full-depth (35.4%*) squats. There were no significant differences between the relative contributions of the BF, the VMO, and the VL at different squatting depths during this phase. The results suggest that the GM, rather than the BF, the VMO, or the VL, becomes more active in concentric contraction as squat depth increases.

So don't go making the mistake of trying to target parts of the quad by different types of squatting, it just doesn't work. Check this thread for more info:

Improving legs

Hi Guys, I'm not satisfied with my legs so I toughed that maybe someone can suggest some good routine/ split that mainly helps to improve overall leg size. I'm currently following split like this: 1.Chest. biceps 2.Legs 3.Off 4.Back, traps 5.Shoulders, triceps. 6.Off 7.Off Should I add...

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PV said:
Nice article tim and nice discussion going on here

All this applies to back squats mostly...so what about front squat? seeing that the heavy load is placed at the front of the body instead of the back which puts more strain in the inner thighs quads and knee's

Any thoughts?

Front squat maintains a more vertical position for the spine thus shifting the load off the hips. The involvement of the quads and hamstrings is roughly the same though, so you are comparitively weaker in this movement. There is no emperical evidence to suggest there is more quad activity and definitely none to suggest any one part is taxed more.

KNEE JOINT KINETICS AND LOWER EXTREMITY MUSCLE ACTIVATION DURING FRONT AND BACK SQUATS
Mark D. Tillman, Jon C. Gullett, Gregory M. Gutierrez, and John W. Chow

INTRODUCTION
Most activities of daily living require the coordinated contraction of several muscle groups simultaneously. Squats require this type of synchronization and are considered one of the most functional and efficient weight-bearing exercises whether an individual’s goals are sport specific or are for an increased quality of life (Lutz et al., 1993). Because a strong and stable knee is extremely important to an athlete’s or patient’s success, an understanding of knee biomechanics while performing the squat is helpful to therapists, trainers, and athletesalike (Escamilla, 2001). Two forms of the squat lift are the back squat and the front squat. Strength and conditioning professionals have recognized the similarities between the lifts, but feel that these variations can be used to protect and isolate different muscle groups. It is believed that the front squat requires lower muscular force in the low back and may also isolate the quadriceps more than back squats. These beliefs are not supported by empirical evidence. The two primary purposes of this study were to determine which squat variation places the least force and torque on the knee and to examine the effects of front and back squats on primary as well as secondary muscle groups. More specifically, we compared the compressive forces, shear forces, and moments applied to the tibiofemoral joint, and lower extremity muscle activity as well.

RESULTS AND DISCUSSION
The back squat resulted in higher
compressive forces on the knee (10.8 ± 2.1
N/kg) than the front squat (9.2 ± 1.5 N/kg)
(t14 = 3.661, P = 0.003). Shear forces at the
knee did not vary between the back and
front squat (t14 = -1.243, P = 0.234).
Extension moments at the knee did not vary
between the two types of squats (t14 = 1.284,
P = 0.220). Bar position did not influence
muscle activity. Univariate tests indicated
that all six muscles were more active (P ≤
0.003) during the ascent phase of the
exercise (Figure 1). By decreasing the
compressive force encountered while
performing squats, the risk of osteoarthritis
and pain may be reduced. Since the muscles
monitored were equally active during the
front squat while lifting a lighter load, it is
presumable that the same workout can be
achieved with less compressive forces on the
knee. This information suggests that front
squats could be advantageous for people
with knee problems such as ligament and
meniscus tears, and for general long-term
joint health.

SUMMARY
The front squat was shown to be just as
effective as the back squat in terms of
overall muscle recruitment, with
significantly less compressive forces on the
knee. This suggests that front squats may be
more beneficial for certain individuals.

So front squats are comparitively better for the knee and lower back when performed correctly. But this is as much about the relative loading of the squat as it is about the biomechanics. Neither can be as abusive as leg presses and leg extensions.

PrinceVegeta · Dec 1, 2008

Thanx for the great explanation my friend!

Daniel Andersson · Dec 1, 2008

Im not doing squats differently because I want to target different parts of my legs no. I do it because I have more then one injury to my legs ,(Quad tear on my left leg, 2 hammy pulls, and my fu**ed up right knee from an accident) Any of the legs can give out without warning...I can "save" the floor in the gym and myself (hopefully :jerkoff1:

) if Im not to deep down in a squat. Before my injuries it was all the way down for all my weights.

Thanks for the info though, always nice to read stuff like that :xyxthumbs:

Squatting depth

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