Biomechanics of the Squat and Deadlift

Table of Contents Introduction ................................................................................................................... 4 Advanced Models .............................................................................................................................................. 4 Assumptions/Limitations ............................................................................................................................. 4

Moment Arms ................................................................................................................ 5

Support Moment ........................................................................................................... 6 Force Sharing ................................................................................................................. 8 Barbell Squat Torques ................................................................................................ 9 Knee Dominant Squat .................................................................................................................................. 10 Hip Dominant Squat ..................................................................................................................................... 11

Barbell Deadlift Torques ......................................................................................... 12 Knee Dominant Deadlift .............................................................................................................................. 12

ROM and Torque ......................................................................................................... 13 Passive-Elastic and Active Muscle Force ............................................................ 14 Sticking Regions.......................................................................................................... 15 Long Femurs in the Squat ........................................................................................................................... 16 The Effect of Femur Length on Maximum Squat Strength............................................................. 17 Long Arms in the Deadlift ........................................................................................................................... 18

Gluteus Maximus EMG and Hip Extension Torque-Angle Curves .............. 20 Effect of Gluteus Maximus Hypertrophy on Maximum Hip Extension Torque............................................................................................................................ 21 Spinal Rounding.......................................................................................................... 23 Spinal Rounding Torques ........................................................................................................................... 23 Spinal Rounding in the Deadlift ............................................................................................................... 23 Spinal Rounding and Spinal Loading ..................................................................................................... 24 Spinal Rounding and Deadlift Muscle Activation .............................................................................. 24

Biomechanics of the Lumbopelvic Hip Complex.............................................. 25 Counterbalance Squat and Torques..................................................................... 26 Trunk Position in the Squat .................................................................................... 27 High Bar vs Low Bar Squats .................................................................................... 28 Squat Variations ......................................................................................................... 29 Front Squat....................................................................................................................................................... 29

2 x 4: Maximum Strength

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Back Squat ........................................................................................................................................................ 29 Box Squat .......................................................................................................................................................... 29 Zercher Squat .................................................................................................................................................. 29

Deadlift Variations ..................................................................................................... 31 Conventional Deadlift .................................................................................................................................. 31 Sumo Deadlift .................................................................................................................................................. 31 Trap Bar Deadlift ........................................................................................................................................... 31 Hack Lift ............................................................................................................................................................ 31

Common “Dysfunctions” .......................................................................................... 33 Knee Valgus ...................................................................................................................................................... 33 Butt Wink .......................................................................................................................................................... 33 Poor Ankle Mobility ...................................................................................................................................... 33 Poor Core Stability ........................................................................................................................................ 34

Dorsiflexion Aids in the Squat ............................................................................... 35 Belts and Intra-Abdominal Pressure ................................................................... 36 Knee Wraps, Suits, Briefs, and Torque................................................................ 37 Theoretical Effects of Support Gear........................................................................................................ 38 Bands, Chains, and Torque ......................................................................................................................... 39 Assistance Lifts ............................................................................................................................................... 40 Hip Thrust......................................................................................................................................................... 41 Back Extension on GHD ............................................................................................................................... 41 45º Hyper.......................................................................................................................................................... 41 Good Morning.................................................................................................................................................. 42 Reverse Hyper................................................................................................................................................. 42 Glute Ham Raise ............................................................................................................................................. 43


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Introduction The word “biomechanics” stems from the Greek language for “life mechanics,” but this doesn’t really tell us much; Oxford tells us a bit more, “the study of the mechanical laws relating to the movement or structure of living organisms.” Biomechanics can refer to a number of subconcentrations, such as fluid dynamics or tissue modeling, but perhaps the most relevant to strength & conditioning is musculoskeletal biomechanics.

Musculoskeletal biomechanics is a subconcentration of biomechanics in which the mechanical laws of physics are applied to the human musculoskeletal system. When one performs a closed chain kinetic movement, their body can be viewed as a system of levers so that the torque on each joint can be calculated. The torque on a joint is indicative of how much turning force is being placed on that joint, which can enable us to estimate how hard a muscle (or group of muscles) has to work to overcome that torque in order to move or prevent the movement of a joint about its axis. Another term for torque is moment. Throughout this text, the biomechanics of the squat, deadlift, and their variations will be discussed, paying particular attention to the effects of technique and form on joint torques.

Advanced Models

In an ideal world, we would use techniques such as muscle modeling, which requires threedimensional motion capture, electromyography, force plates, and specialized software to help us calculate precise and individualized biomechanical evaluations. Unfortunately, this equipment costs hundreds of thousands of dollars and is only used in extensive biomechanics laboratories. However, this does not mean that biomechanical principles cannot be applied using the naked eye.

Assumptions/Limitations

Throughout this text, certain assumptions are made, as we do not have access to the advanced modalities previously described. Assumptions and limitations within this text are as follows: • •

• • • • • • • • • • •

Assuming that the lifter pushes through the center of the foot Assuming that the center of gravity is positioned near the load itself in the barbell squat and through the scapula for the barbell deadlift Ignoring muscle co-contractions Ignoring electromyography (EMG) Focusing on external load, not system mass (ignoring superincumbent bodyweight) Not using video capture and force plates Not using inverse dynamics or 3D modeling Focusing only on vertical forces during the squat and deadlift Ignoring momentum, looking at instantaneous torques using quasi-static models Assuming that the plate radius is 22.5cm Omitting hand length with regards to grip in the deadlift Assuming a high bar squat position Assuming that the spine stays rigid and no pelvic tilt exists


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Moment Arms In physics, a moment arm is simply the perpendicular distance from the axis of rotation to the line of action of the force. In biomechanics, there are two types of moment arms that you should be familiar with. There’s the muscle moment arm, which is internal and represents the leverage of a muscle (perpendicular distance between the joint center and muscle line of pull), and there’s the resistance moment arm, which is external and represents the perpendicular distance between the load and the joint center. This text will focus on resistance moment arms.

With squats, the moment arm (sometimes called lever arm) can be estimated by examining the horizontal distance between the joint center and the ground reaction force vector. With heavy loads, we can assume that the horizontal component of the ground reaction force vector is negligible. Therefore, the ground reaction force vector is perpendicular to the ground and is formed by drawing a line that connects the center of gravity and center of pressure through the feet, as depicted to the left. A compound movement consists of moving multiple levers about multiple joints in order to complete a movement. For example, during the deadlift, knee extension and hip extension occur simultaneously. This is drastically different from isolation movements such as the preacher curl whereby elbow flexion is the only joint action occurring. During the preacher curl, the humerus (upper arm) is in a fixed position such that the forearm must rotate about a fixed axis, and thus not leaving much room to modify the movement. Compound movements have more degrees of freedom, or more ways to complete the movement, consequently making compound movements more complicated, harder to analyze, and more unique from person-to-person.

Moment arms of the knee and hip during a squat.


Movement variation between individuals is not necessarily a bad thing, but it can help identify strengths and weaknesses during movement by calculating joint torques and seeing how different lifters “favor” different joints.

This manual uses computer-aided design (CAD) drawings drawn to scale in order to depict the changing moment arms and subsequent changing joint torques associated with lower body exercise, paying particular attention to the barbell squat and deadlift.

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Support Moment Using the moment arm and load being used (along with the superincumbent bodyweight, or mass of the bodyweight above the joint being examined in standing exercises), torques can be calculated. Torque (τ) is the product of the force and moment arm, as described in the equation below where r is the length of the moment arm in meters and F is the force in Newtons. 𝝉𝝉 = 𝑭𝑭 ∗ 𝒓𝒓

In biomechanics, torque is calculated using Newton meters (Nm). Newtons are the SI unit of force. Because gravity on Earth is constant, we can use 9.8 m/s2 for a (we’ll round up to 10 for the sake of simplicity in this manual), and simply substitute the mass of the load in kilograms for m (we’ll use 100 kg throughout this text). The equation below will calculate the force in Newtons using the units described. 𝑭𝑭 = 𝒎𝒎 ∗ 𝒂𝒂

When calculating torque, the force will be constant and the length of the moment arm will determine differences in torque. With explosive lifts, you’d need to deal with momentum, but with heavy lifts, this momentum can be ignored, as quasi-static models with lifts taking more than 2-seconds have been shown to be 99% as accurate as dynamic models (Lander et al., 1990). Variations in form and lever length will show that a movement can be completed using an infinite number of torque and moment variations.

In many activities, it is surprising to find that the body tends to distribute a fairly consistent total amount of joint torque independent of the movement style between the three primary lower body joints. For example, let’s say that 200 Nm of lower body extensor torque is required to lift a box. The body could move mostly at the hips and utilize 150 Nm of hip extension torque and 25 Nm of ankle plantar flexion and knee extension torque to achieve the task. It could also produce 120 Nm of knee extension torque, 50 Nm of hip extension torque, and 30 Nm of plantar flexion torque. The take-away point here is that there are many movement patterns that can lead to successful lifting outcomes, and the various lifting styles tend to require similar total extensor torques but with different distributions across the various joints. See the three pictures below representing a lifter picking up a 20-kg box with a kneedominant style, a blended style, and a hip-dominant style; the combined hip and knee moments of the three variations is 84.36 Nm, 84.54 Nm, and 82.56 Nm, respectively.

In this manual, 𝝉𝝉𝑯𝑯 will stand for hip extension torque, while 𝝉𝝉𝑲𝑲 will stand for knee extension torque.


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Examples 𝑭𝑭 = 𝒎𝒎 ∗ 𝒂𝒂 𝑭𝑭 = 20 𝑘𝑘𝑘𝑘 ∗ 10 𝑚𝑚�𝑠𝑠 2 𝑭𝑭 = 200 𝑁𝑁

𝝉𝝉𝑯𝑯 = 200 𝑁𝑁 ∗ 0.1535 𝑚𝑚 𝝉𝝉𝑯𝑯 = 30.7 𝑁𝑁𝑁𝑁



𝝉𝝉 = 30.7 𝑁𝑁𝑁𝑁 + 53.66 𝑁𝑁𝑁𝑁 𝝉𝝉 = 84.36 𝑁𝑁𝑁𝑁

𝝉𝝉 = 61.94 𝑁𝑁𝑁𝑁 + 22.58 𝑁𝑁𝑁𝑁 𝝉𝝉 = 84.54 𝑁𝑁𝑁𝑁

𝝉𝝉 = 91.42 𝑁𝑁𝑁𝑁 − 7.78 𝑁𝑁𝑁𝑁 𝝉𝝉 = 82.56 𝑁𝑁𝑁𝑁

𝝉𝝉𝑲𝑲 = 200 𝑁𝑁 ∗ 0.2683 𝑚𝑚 𝝉𝝉𝑲𝑲 = 53.66 𝑁𝑁𝑁𝑁



Lander, J. E., Simonton, R. L., & Giacobbe, J. K. (1990). The effectiveness of weight-belts during the squat exercise. Medicine and science in sports and exercise, 22(1), 117-126.


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Force Sharing It is not uncommon for more than one muscle to be able to control for the same joint action, illustrated by the actions of the gluteus maximus and hamstrings on hip extension. How much each muscle contributes to a joint action depends on a number of factors, including the joint angle and the strength of each muscle, but these factors are not universal. For example, the prime mover of the hip thrust is the gluteus maximus, but the hamstrings contribute to hip extension as well, so hip extension forces are not mutually exclusive to one muscle. The contribution of a muscle to a movement on a joint is not the same in every person, thus exercises must be chosen in accordance to how that individual can activate the intended target musculature.

Studies show that with cueing and focus of attention, one can change the amount of EMG activity in the various synergists during a movement involving multiple muscles (Lewis & Sahrman, 2009). For example, using more glutes during hip extension will cause a decrease in hamstring activation. What’s more, this force sharing has been shown to be easier to do with lighter loads compared to maximal loads (Snyder & Fry, 2012). Although we can assume that if a movement produces a large magnitude of hip extension torque, it will be a good movement for the gluteus muscles, we must be careful with our assumptions as the movement could be carried out largely by the hamstring and adductor muscles. Lewis, C. L., & Sahrmann, S. A. (2009). Muscle activation and movement patterns during prone hip extension exercise in women. Journal of athletic training, 44(3), 238.

Snyder, B. J., & Fry, W. R. (2012). Effect of Verbal Instruction on Muscle Activity During the Bench Press Exercise. The Journal of Strength & Conditioning Research, 26(9), 2394-2400.


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Barbell Squat Torques During the torque calculation of a squat, as seen in the drawing below, we can assume that the center of the barbell falls in line with the gravitational force vector (the lifter does not shift the barbell too far forward or backward relative to the midfoot). A line representing the gravitational force vector should be drawn through the bar and center of pressure of the feet (assumed to be midfoot), as shown below. This line should be perpendicular to the ground (we can assume that most of the force is vertical during a squat). In order to calculate hip and knee torques, lines representing the moment arms should be drawn perpendicularly from the ground reaction force vector to each of the said joint centers, as depicted below. Remember, we are ignoring body mass and focusing on barbell mass. If we wanted to be more accurate, we would look at system mass, which includes both, however, this allows for simpler calculations. 𝑭𝑭 = 𝒎𝒎 ∗ 𝒂𝒂 𝑭𝑭 = 100 𝑘𝑘𝑘𝑘 ∗ 10 𝑚𝑚�𝑠𝑠 2 𝑭𝑭 = 1000 𝑁𝑁 Because the measurements given are in centimeters, we will convert them to meters: 1 𝑚𝑚 21.22 𝑐𝑐𝑐𝑐 ∗ = 0.2122 𝑚𝑚 = 𝒓𝒓 100 𝑐𝑐𝑐𝑐 𝝉𝝉 = 𝑭𝑭 ∗ 𝒓𝒓 𝝉𝝉 = 1000 𝑁𝑁 ∗ 0.2122 𝑚𝑚 = 212.2 𝑁𝑁𝑁𝑁 The torque at both the hips and knees is 212.2 Nm.

To the left is the “ideal” squat, that is, the moment arms are equal to one another to balance out the torques on the joints. However, this is not a perfect world and people often do not squat with equal moments. Powerlifters tend to squat with greater hip moments while Olympic weightlifters tend to squat with more equal hip and knee moments. There are two variations to any squat: a knee dominant and hip dominant version (actually there’s a continuum with every possible combination in between). Learning how to adjust the torques depending on the task at hand will enable the lifter or coach to make better decisions in programming and training.


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Knee Dominant Squat

Below is a free body diagram representing a lifter that has a knee dominant squat. The individual’s trunk is more upright which decreases the hip moment and increases the knee moment. Because the knee moment is now greater, the individual must overcome a greater knee torque in order to move the weight. The torques can be calculated as follows: 𝝉𝝉 = 𝑭𝑭 ∗ 𝒓𝒓 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.1414 𝑚𝑚 = 141.4 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.2829 𝑚𝑚 = 282.9 𝑁𝑁𝑁𝑁


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Hip Dominant Squat A hip-dominant squat is just the opposite of a knee dominant squat, that is, the individual leans forward and sits back more, which in turn increases the hip moment and decreases the knee moment. The hips now have more torque to overcome and the knees have less. Hip-dominant squat torques can be calculated like so: 𝝉𝝉 = 𝑭𝑭 ∗ 𝒓𝒓 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.2829 𝑚𝑚 = 282.9 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.1414 𝑚𝑚 = 141.4 𝑁𝑁𝑁𝑁


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Barbell Deadlift Torques The torque of a deadlift is calculated similarly to that of the squat, and again, it is safe to assume that the center of the barbell is the center of gravity, thus, it is where we draw the gravitational force vector. As one would probably think, the deadlift is a very hip dominant movement when compared to the squat, as seen below. 𝑭𝑭 = 𝒎𝒎 ∗ 𝒂𝒂 𝑭𝑭 = 100 𝑘𝑘𝑘𝑘 ∗ 10 𝑚𝑚�𝑠𝑠 2 𝑭𝑭 = 1000 𝑁𝑁 Because the measurements given are in centimeters, we will convert them to meters: 1 𝑚𝑚 45.71 𝑐𝑐𝑐𝑐 ∗ = 0.4571 𝑚𝑚 = 𝒓𝒓 100 𝑐𝑐𝑐𝑐 𝝉𝝉 = 𝑭𝑭 ∗ 𝒓𝒓 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.4571 𝑚𝑚 = 457.1 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.0389 𝑚𝑚 = −38.9 𝑁𝑁𝑁𝑁

Knee Dominant Deadlift

𝝉𝝉 = 𝑭𝑭 ∗ 𝒓𝒓 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.3879 𝑚𝑚 = 387.9 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.0290 𝑚𝑚 = 29.0 𝑁𝑁𝑁𝑁 As you can see, the hip and knee dominant deadlifts are quite different than those of the squat. The top image actually involves a knee-flexion net moment where the hamstrings dominate the quadriceps, whereas the bottom image shows a knee-extension net moment where the quadriceps dominate the hamstrings. However, the net torques are only around 70Nm apart. Any way you slice it, the deadlift is a hip dominant movement.


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ROM and Torque Once one has basic knowledge of the workings of torque, it is easy to see how range of motion affects the torque placed on joints. In the picture below, you’ll see a parallel squat and a quarter squat. Assume a 100kg load for the parallel squat and 115kg load for the quarter squat.

𝝉𝝉 = 1000 𝑁𝑁 ∗ 0.2121 𝑚𝑚 𝝉𝝉 = 212.1 𝑁𝑁𝑁𝑁

𝝉𝝉 = 1150.02 𝑁𝑁 ∗ 0.1844 𝑚𝑚 𝝉𝝉 = 212.1 𝑁𝑁𝑁𝑁

As you can probably imagine, similar torques are created with partial movements compared to full range movements because more load can be utilized. In the above example, one would need 15% more load to make up for less ROM (right) in order to match the torques placed on his joints in the deeper squat (left). The full range movements possess greater moment arms with lower forces, while the partial movements possess smaller moment arms with greater forces. Since torque equals perpendicular force times the length of the moment arm, you end up with similar torques. It should be noted, however, that full range movements tend to produce greater hypertrophic adaptations in the literature (Bloomquist et al., 2013). Bloomquist, K., Langberg, H., Karlsen, S., Madsgaard, S., Boesen, M., & Raastad, T. (2013). Effect of range of motion in heavy load squatting on muscle and tendon adaptations. European journal of applied physiology, 1-10. 2 x 4: Maximum Strength

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Passive-Elastic and Active Muscle Force There are two forces that make up total muscle forces: passive-elastic and active. As one would probably guess, active forces originate from the contracting muscles, but passiveelastic forces are less heard of. A passive-elastic force is simply the force generated from the elasticity in passive tissue structures, such as tendons and the elastic properties of muscle. They’re called into play when the structure is stretched and are for the most part independent of active contraction. However, titin, a large molecule in the sarcomere, elicits much more passive force when activated and stretched.


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Sticking Regions Everybody has a weak point, or sticking region, in the squat and deadlift. These become especially apparent at near-maximal loads and tend to be different for everyone, but why do these sticking points occur?

Various theories have been presented, but here, we are going to concentrate on two of those theories. The first being that sticking regions are caused by the lifter running out of passive forces, for example from titin and other passive tissues, and having to switch over to purely active, contractile forces. This seems to be the case in the bench press (Elliot et al., 1989). This is most likely the cause of most sticking regions.

Another theory is that the body acts like a spring, especially in large individuals. Let’s take the squat, for example. As one descends, their hamstrings will make contact with their calves and their belly will make contact with their thigh. These tissues pressing against one another will create contributory passive forces in the bottom of a lift. This is not the case for every individual and varies greatly between lifters depending on their form, depth, and size. Where sticking regions occur seems to differ greatly from individual to individual, but they are similar between lifts in the same individual. For example, person A will have a similar sticking region in both the sumo and conventional deadlift, but those sticking regions will differ from person B’s sticking regions in the sumo and conventional deadlift (McGuigan & Wilson, 1996).

It should be noted that often the sticking regions in the squat and the deadlift occur at different joint angles. For the hips, the sticking points are at 82º and 96º for the squat and deadlift, respectively. For the knees, the sticking points are at 101º and 155º for the squat and deadlift, respectively. These data indicate that one lift does not necessarily carry over to the other lift, as sticking points are significantly different from one another (Hales et al., 2009).

Elliott, B. C., Wilson, G. J., & Kerr, G. K. (1989). A biomechanical analysis of the sticking region in the bench press. Medicine and Science in Sports and Exercise, 21(4), 450.

McGuigan, M. R., & Wilson, B. D. (1996). Biomechanical analysis of the deadlift. The Journal of Strength & Conditioning Research, 10(4), 250-255. Hales, M. E., Johnson, B. F., & Johnson, J. T. (2009). Kinematic analysis of the powerlifting style squat and the conventional deadlift during competition: is there a cross-over effect between lifts?. The Journal of Strength & Conditioning Research, 23(9), 2574-2580.


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Anthropometry and Torque (Lightning Bolt) The length of one’s limbs and trunk have a large effect on the torques their bodies must produce in order to move a load. Every individual possesses an inherent “lightning bolt” when you consider the anatomical lengths of their torsos, femurs, and tibias. These limb length proportions determine much of what form looks like in a squat. Technique, muscle strengthening, and motor control can certainly alter form, but there’s only so much one can do, especially with extreme proportions.

Long Femurs in the Squat

The Crural Index is the ratio of the length of the lower leg to that of the upper leg. If one has a low Crural Index, that is, longer femurs, it puts the lifter in a disadvantageous position during the squat. The next page shows a comparison of a squatter with normal femur length with a squatter with short femurs and a squatter with long femurs. Taken to an extreme level, if most of the total “lightning bolt” is taken up by the spine and tibias, the lifter will stay upright and be much stronger in the squat as a result. Conversely, if most of the total “lightning bolt” is taken up by the femur, the lifter will fold like an accordion and be weaker in the squat as a result.

Take world-class 114-pound Polish powerlifter Andrzej Stanaszek, for example. Stanaszek is a dwarf, meaning he has disproportionately short limbs and is less than 4’10 (he actually stands under 4’). These proportions give him a mechanical advantage to lift huge loads, including a 662.5 lb squat and 402.3 lb bench press. Both the bench and squat favor shorter limbs. Click HERE to see his squat. Ironically, these same proportions don’t appear to help him in the deadlift - HERE Andrzej fails with 319 lbs.


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Below are squats and their moment arms for a normal sized femur, disproportionately long femur (+20%), and disproportionately short femur (-20%), respectively.

Medium Femurs 𝝉𝝉 = 1000 𝑁𝑁 ∗ 0.2122 𝑚𝑚 𝝉𝝉 = 212.2 𝑁𝑁𝑁𝑁

Long Femurs 𝝉𝝉 = 1000 𝑁𝑁 ∗ 0.2546 𝑚𝑚 𝝉𝝉 = 254.6 𝑁𝑁𝑁𝑁

Short Femurs 𝝉𝝉 = 1000 𝑁𝑁 ∗ 0.1697 𝑚𝑚 𝝉𝝉 = 169.7 𝑁𝑁𝑁𝑁

The resulting knee and hip torques are directly proportional to the increase or decrease in femur length (20%). As you can imagine, having shorter femurs confers a distinct advantage in the squat!

The Effect of Femur Length on Maximum Squat Strength

Now, let’s say we have two individuals: one with short femurs and one with long femurs (as seen above). How does femur length and its effects on torque requirements affect how much one can lift? Well, let’s find out. Let’s assume each lifter possesses 500Nm of hip extension torque and 400Nm of knee extension torque at the bottom of the squat, which would make them highly advanced powerlifters.


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Long Femurs 400 𝑁𝑁𝑁𝑁 𝑭𝑭𝑲𝑲 = 0.2546 𝑚𝑚

𝑭𝑭𝑲𝑲 = 1571.09 𝑁𝑁

500 𝑁𝑁𝑁𝑁 𝑭𝑭𝑯𝑯 = 0.2546 𝑚𝑚 𝑭𝑭𝑯𝑯 = 1963.86 𝑁𝑁

𝜮𝜮𝜮𝜮 = 𝑭𝑭𝑯𝑯 + 𝑭𝑭𝑲𝑲 𝜮𝜮𝜮𝜮 = 1571.09 𝑁𝑁 + 1963.86 𝑁𝑁 𝜮𝜮𝜮𝜮 = 3534.95 𝑁𝑁 = 796.35 lbs

Short Femurs 400 𝑁𝑁𝑁𝑁 𝑭𝑭𝑲𝑲 = 0.1697 𝑚𝑚 𝑭𝑭𝑲𝑲 = 2357.10 𝑁𝑁

500 𝑁𝑁𝑁𝑁 0.1697 𝑚𝑚 𝑭𝑭𝑯𝑯 = 2946.38 𝑁𝑁 𝑭𝑭𝑯𝑯 =

𝜮𝜮𝜮𝜮 = 𝑭𝑭𝑯𝑯 + 𝑭𝑭𝑲𝑲 𝜮𝜮𝜮𝜮 = 2357.10 𝑁𝑁 + 2946.38 𝑁𝑁 𝜮𝜮𝜮𝜮 = 5393.48 𝑁𝑁 = 1,215.04 lbs

According to these estimations, a squatter with 20% shorter femurs with the same amount of knee and hip extension torques can squat 41.6% more than a squatter with 20% longer femurs. In fact, reducing femur length transformed the powerlifter from strong to world record holder!

Long Arms in the Deadlift

Because the starting position of the deadlift is determined by an individual’s arm length, an individual with longer arms is at a much greater mechanical advantage than an individual with shorter arms. This is due to the peak torque of a deadlift being at the bottom of the movement. A more vertical trunk angle can be seen in the diagrams below just adding length to the arms of the lifter without altering leg and torso lengths.

Lamar Gant is a great example of a phenomenal deadlifter with long arms. At a bodyweight of 132, Gant was able to pull 683.4 lbs. Click HERE to watch Lamar’s deadlift – notice that he locks out with the bar resting just above the kneecaps. The free body diagram on the following page shows why and is drawn similarly to the squats in that the arms were either shortened or elongated by 20%. The first image is normal length, second is shortened, and third is elongated.


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Medium Arms 𝝉𝝉 = 1000 𝑁𝑁 ∗ 0.4571 𝑚𝑚 𝝉𝝉 = 457.1 𝑁𝑁𝑁𝑁

Short Arms 𝝉𝝉 = 1000 𝑁𝑁 ∗ 0.4610 𝑚𝑚 𝝉𝝉 = 461.0 𝑁𝑁𝑁𝑁

Long Arms 𝝉𝝉 = 1000 𝑁𝑁 ∗ 0.4326 𝑚𝑚 𝝉𝝉 = 432.6 𝑁𝑁𝑁𝑁

The resulting hip torques are directly proportional to the increase or decrease in arm length (20%). In addition the joints have to move through a much larger range of motion, which will lead to greater fatigue throughout the lift. As you can imagine, having longer arms confers a distinct advantage in the deadlift!


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Gluteus Maximus EMG and Hip Extension Torque-Angle Curves Worrell et al. (2001) investigated gluteus maximus EMG and its relation to hip extension torque, and the findings are puzzling to say the least. Below is a rendition of Figure 6 from the study.

Subjects performed maximal hip extension torque at four different angles of hip flexion. As

you can see, hamstring EMG does not change very much throughout the hip range of motion, however, gluteus maximus EMG rises from a flexed to an extended hip position. Interestingly, hip extension torque is greater in a hip flexed position compared to a hip extended position. Why this occurs is not fully understood. We are probably stronger in hip flexion due to the increased involvement of the adductors in hip extension. The glutes probably fire harder at end range hip extension to compensate for their shorter lengths or because they have better leverages at that range of motion. These findings are highly applicable to training as they explain how the muscle works and provide some insight as to the best way to train the gluteus maximus. If one wants to optimize the gluteus maximus hypertrophic response, he or she needs to incorporate multiple hip extension movements such as hip thrusts, squats, and deadlifts. Worrell, T. W., Karst, G., Adamczyk, D., Moore, R., Stanley, C., Steimel, B., & Steimel, S. (2001). Influence of joint position on electromyographic and torque generation during maximal voluntary isometric contractions of the hamstrings and gluteus maximus muscles. The Journal of orthopaedic and sports physical therapy, 31(12), 730. 2 x 4: Maximum Strength

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Effect of Gluteus Maximus Hypertrophy on Maximum Hip Extension Torque It is well known that when a muscle is hypertrophied, it is also stronger. This is due to the increase in physiological cross sectional (PCSA). Let’s quickly familiarize ourselves with a few formulas pertaining to muscle PCSA and its relationship to torque. 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 (𝑐𝑐𝑐𝑐2 ) =

𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣 (𝑐𝑐𝑐𝑐3 ) 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙ℎ (𝑐𝑐𝑐𝑐)

𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 (𝑁𝑁) = 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 (𝑐𝑐𝑐𝑐2 ) ∗ 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 (𝑁𝑁�𝑐𝑐𝑐𝑐2 )

Specific tension refers to the force exerted by the fibers per unit of PCSA. This would be measured in N/cm2. Muscle force denotes how much force the muscle pulls with, but as we know from previous sections in this text, we care about torque.

In order to calculate the muscle moment (torque), we must multiply the muscle force by the perpendicular distance from the muscle’s line of pull to the joint center. The following image shows how hypertrophy can affect the muscle’s moment arm and therefore, moment.


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As you can see, as a muscle hypertrophies, it not only gets larger and farther from the joint center, but the angle of the fibers also change, thus giving it a larger capacity for torque development. Below is an example of how someone’s hip extension torque would change as a result of a 31.85% increase in gluteus maximus size.

𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 = 28.92 𝑐𝑐𝑐𝑐2 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 = 28.92 𝑐𝑐𝑐𝑐2 ∗ 61 𝑁𝑁�𝑐𝑐𝑐𝑐2 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 = 1,764.12 𝑁𝑁

𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 = 38.13 𝑐𝑐𝑐𝑐2 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑒𝑒 = 38.13 𝑐𝑐𝑐𝑐2 ∗ 61 𝑁𝑁�𝑐𝑐𝑐𝑐2 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 = 2,325.93 𝑁𝑁

Muscle Moment 1,687.04 𝑁𝑁 ∗ 0.0469 𝑚𝑚 = 79.12 𝑁𝑁𝑁𝑁

Muscle Moment 2,325.93 𝑁𝑁 ∗ 0.0567 𝑚𝑚 = 131.88 𝑁𝑁𝑁𝑁

Muscle force corrected for angle of insertion 1764.12 𝑁𝑁 ∗ sin 73º = 1,687.04 𝑁𝑁

Muscle force corrected for angle of insertion 2325.93 𝑁𝑁 ∗ sin 90º = 2,325.93 𝑁𝑁

Thus, a gluteus maximus that is 31.85% larger can produce 50% more hip extension torque.


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Spinal Rounding Some amount of spinal rounding, specifically in the thoracic region, is acceptable when approaching maximal loads in the deadlift. Some lifters are strongest when maintaining a good arch, while others are strongest when they round their spines. You want to make sure the rounding is in the upper back and that lower back (lumbar) rounding is kept to a minimum when pulling heavy loads. Here is why you may be stronger when rounding the upper back.

Spinal Rounding Torques

Depicted below is a conventional deadlift for a lifter with a “neutral” spine, and the same lifter pulling with a rounded spine. By rounding the spine, the individual is able to decrease the hip moment, which decreases hip torque and in turn makes the load easier to lift.

Straight Back

𝝉𝝉 = 1000 𝑁𝑁 ∗ 0.4571 𝑚𝑚 𝝉𝝉 = 457.1 𝑁𝑁𝑁𝑁

Rounded Back

𝝉𝝉 = 1000 𝑁𝑁 ∗ 0.4337 𝑚𝑚 𝝉𝝉 = 433.7 𝑁𝑁𝑁𝑁

With a 45º arch, the moment arm on this individual shortens by around 5%. A 5% decrease in torque could mean the difference between finishing a pull and not, especially in competition. Rounding also places the places the muscles at different starting lengths, especially if the pelvis changes position. The pelvis modulates hip extensor length, with anterior tilting placing the hip extensors at longer lengths and posterior tilting placing the hip extensors at shorter lengths. How this impacts strength is not very clear, but it may depend on the individual.

Spinal Rounding in the Deadlift

There are several other strength benefits to spinal rounding in addition to its effects on joint torques, including: 2 x 4: Maximum Strength

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• • • •

Increased Intra-Abdominal Pressure – Provides additional spinal stabilization. Passive Erector Support – Titin filaments within the thoracic erectors and tendons will provide resistance to stretch, similar to the way a spring works. Spinal ligaments, fascia, joints, and discs – When one approaches full flexion, these are more or less the body’s last chance to support itself. One should not rely on these structures, but they do provide support if need be. Support from the rib cage and sternum – According to Watkins IV et al. (2005), the sternocostal complex has been shown to increase thoracic spine stability during flexion/extension by 40%.

For more information on the benefits of spinal rounding in the deadlift, check out Bret Conteras’ article on T-Nation, A Strong Case For The Rounded Back Deadlift.

Watkins IV, R., Watkins III, R., Williams, L., Ahlbrand, S., Garcia, R., Karamanian, A., ... & Hedman, T. (2005). Stability provided by the sternum and rib cage in the thoracic spine. Spine, 30(11), 1283-1286.

Spinal Rounding and Spinal Loading

Shearing forces occur when two parts of the body are not aligned which pushes one part of the body in one direction, and another part of the body in the other direction. This is vastly different from compression forces, for which intervertebral discs are designed to handle efficiently. When performing a lift, whether in the gym or in daily life, one should consider the ramifications of shearing forces on spine health. While the dangers of shear loading may be grossly exaggerated, spinal rounding undoubtedly places the discs and ligaments under much greater load. Therefore, spinal rounding should be utilized sparingly, if ever.

Information from: McGill, S. (2007). Low back disorders: evidenced-based prevention and rehabilitation. Human Kinetics.

Spinal Rounding and Deadlift Muscle Activation

When one rounds his or her spine, the ratio of active to passive forces acting on trunk extension decreases for the reasons described in the previous sections. In full stretch, the erectors actually shut off, which is deemed “myoelectric silence.” This means that spinal erector activation would decrease and, instead, passive tissues would support the spine.


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Biomechanics of the Lumbopelvic Hip Complex The lumbar spine, pelvis, and hips make up the lumbopelvic hip complex. Learning how to properly control and move through this complex can be difficult and daunting, but doing so will result in a safer, more efficient lift.

One must keep in mind that these structures affect how one’s lumbar spine moves as well, hence the lumbo in lumbopelvic. For example, if one cannot flex at the hip joint any further, they will compensate via posterior pelvic tilt and lumbar flexion. During periods of deep hip flexion, such as the bottom of the squat, it may be beneficial to maintain anterior pelvic tilt because 1) it will put more tension on the adductors and hamstrings and 2) the glutes are already inhibited due to deep hip flexion. As for near lockout, such as the top of a deadlift, the opposite is true: increased posterior pelvic tilt will be a more advantageous position to produce hip extension torque because the gluteus maximus can better activate in this position. Intimately involved in the lumbopelvic hip complex are four different muscles groups: hip abductors, hip adductors, hip flexors, and hip extensors; one’s structure/anatomy greatly affects how these function by either increasing or decreasing the moment arm of each muscle. For example, a 2cm superior displacement of the hip joint center decreases the moment generating capacity of the hip abductors by 49% and hip flexors by 22%. A hip center displaced 2cm superiorly, 2cm laterally, and 2cm anteriorly was shown to maximize hip extension torque (Delp & Maloney, 1993). Bret does a phenomenal job introducing and further explaining the lumbopelvic hip complex and these concepts in this video.

Delp, S. L., & Maloney, W. (1993). Effects of hip center location on the moment-generating capacity of the muscles. Journal of biomechanics, 26(4), 485-499.


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Counterbalance Squat and Torques The counterbalance squat is a variation of the squat in which weight is held out in front of one’s body. This will shift the center of mass forward, which will allow a person to sit back more in order to counteract this shift. The counterbalance is commonly done to help someone learn the squat or learn pistol squats. The change in moment arms resulting from this shift in center of gravity increases hip torque and decrease knee torque. Lynn et al. (2012) looked at the effects of a counterbalance squat vs. regular squats. This shows the effects of shifting the system center of mass forward on forward trunk lean, which decreases knee extension torque while increasing hip extension torque.

Goblet Squat 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.1982 𝑚𝑚 𝝉𝝉𝑯𝑯 = 198.2 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.2261 𝑚𝑚 𝝉𝝉𝑲𝑲 = 226.1 𝑁𝑁𝑁𝑁

Counterbalance Squat 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.3183 𝑚𝑚 𝝉𝝉𝑯𝑯 = 318.3 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.1060 𝑚𝑚 𝝉𝝉𝑲𝑲 = 106.0 𝑁𝑁𝑁𝑁

Lynn, S. K., & Noffal, G. J. (2012). Lower Extremity Biomechanics During a Regular and Counterbalanced Squat. The Journal of Strength & Conditioning Research, 26(9), 2417-2425.


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Trunk Position in the Squat One can change the torques of a squat simply by changing trunk position. When one leans forward, as seen below, he or she is shifting the torques by decreasing the knee moment and increasing the hip moment. This is simply another way of sparing the knees, which may be an individual’s weak link. The opposite is true for someone staying upright, in that they are sparing their hips (and also lower back) and transferring torque to their knees by shifting position to increase the knee moment and decrease the hip moment.

Some variables that may also affect trunk position are: • Dorsiflexion ROM – If one cannot adequately dorsiflex, the knee cannot go forward, therefore he or she must compensate at the hips by leaning forward more or by rounding the spine. Otherwise, the lifter would fall backwards. • Tibia Length – A short tibia means, at the same angle of dorsiflexion, one’s hip moment arm is greater than that of a person with a longer tibia. • Femur Length – At the same angle of dorsiflexion, a person with a long femur will have a greater hip moment arm than a person with a short femur, meaning he or she will need to lean forward more to keep the center of gravity over the feet. • Strength Compensation – As noted above, if one has weak knee extensors and strong hip extensors, it may be beneficial to keep the knee moment small and compensate by more forward lean. This is often seen mid-lift, i.e., the lifter “runs out” of knee extension strength/torque, shifts the hips back to increase the hip moment and decrease the knee moment (which also increases the spinal moment). This shift in hips also increases hamstring length and allows for greater force output so the lifter can finish the lift.

Moderate Lean 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.2122 𝑚𝑚 𝝉𝝉𝑯𝑯 = 212.2 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.2122 𝑚𝑚 𝝉𝝉𝑲𝑲 = 212.2 𝑁𝑁𝑁𝑁


Upright Torso 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.1733 𝑚𝑚 𝝉𝝉𝑯𝑯 = 173.3 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.2510 𝑚𝑚 𝝉𝝉𝑲𝑲 = 251.0 𝑁𝑁𝑁𝑁

Marked Forward Lean 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.2510 𝑚𝑚 𝝉𝝉𝑯𝑯 = 251.0 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.1733 𝑚𝑚 𝝉𝝉𝑲𝑲 = 173.3 𝑁𝑁𝑁𝑁

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High Bar vs Low Bar Squats When one places the bar lower on the back, he or she must compensate by leaning forward more. This makes low bar squats more hip dominant when compared to high bar, as shown below. Notice the greater hip extension moments and lesser knee extension moments in the low bar squat compared to the high bar squat.

High Bar Squat 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.21215 𝑚𝑚 𝝉𝝉𝑯𝑯 = 212.15 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.21215 𝑚𝑚 𝝉𝝉𝑲𝑲 = 212.15 𝑁𝑁𝑁𝑁 2 x 4: Maximum Strength

Low Bar Squat 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.3012 𝑚𝑚 𝝉𝝉𝑯𝑯 = 311.2 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.1231 𝑚𝑚 𝝉𝝉𝑲𝑲 = 123.1 𝑁𝑁𝑁𝑁

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Squat Variations There are four primary variations of the squat: the front squat, back squat, box squat, and Zercher squat. Each one of these variations distributes torques differently and those torque distribution differentiations should be taken advantage of, especially to work on weak points and during times of injury.

Front Squat

During the front squat, the bar is placed across one’s shoulders and is supported by the hands. Shifting the bar forward shifts the center of gravity forward, which in turn allows the lifter to stay more upright. This upright position spares the hips and low back by placing more torque on the knees, making the front squat a knee dominant movement.

Back Squat

The most popular of the squat variations is the back squat. During the back squat, the bar is placed on the upper trapezius and the bar is stabilized with the lifter’s hands. This allows the lifter to go through a more natural range of motion.

Box Squat

Box squats are very similar to back squats, but at the bottom portion, the lifter must sit on a box. Typically, this movement allows the lifter to keep their shins more vertical as the lifter leans forward to keep the center of mass over their feet. This alleviates stress on the knees and makes the movement much more hip dominant than the typical back squat.

Zercher Squat

The Zercher squat is the most unique of the bunch in that instead of the weight resting on the trunk, it is being held in the lifter’s elbows. This variation is somewhere between the front squat and back squat in terms of hip and knee joint torques. Below is a comparison of all four variations.


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Front Squat 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.1766 𝑚𝑚 𝝉𝝉𝑯𝑯 = 176.6 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.2477 𝑚𝑚 𝝉𝝉𝑲𝑲 = 247.7 𝑁𝑁𝑁𝑁

Box Squat 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.4240 𝑚𝑚 𝝉𝝉𝑯𝑯 = 424.0 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 𝑛𝑛/𝑎𝑎


Back Squat 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.2122 𝑚𝑚 𝝉𝝉𝑯𝑯 = 212.2 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.2122 𝑚𝑚 𝝉𝝉𝑲𝑲 = 212.2 𝑁𝑁𝑁𝑁

Zercher Squat 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.3627 𝑚𝑚 𝝉𝝉𝑯𝑯 = 372.7 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.0516 𝑚𝑚 𝝉𝝉𝑲𝑲 = 51.6 𝑁𝑁𝑁𝑁

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Deadlift Variations Similar to the squat, there are variations of the deadlift that make use of different combinations of torque in order to complete the lift.

Conventional Deadlift

Obviously the most popular variation of the deadlift, the conventional deadlift, is performed with the legs in between the arms. This variation is the most hip dominant.

Sumo Deadlift

Powerlifters often utilize the sumo deadlift. By abducting and externally rotating the legs, they can decrease the hip moment arm and perform the lift in a more upright position since hip abduction brings their body closer to the bar.

Trap Bar Deadlift

The trap bar deadlift utilizes a trap bar rather than a barbell. This allows the load to be shifted more posteriorly when compared to the conventional deadlift, and has similar torque values to that of a squat. Some people refer to this as a squat/deadlift hybrid, or a squat-lift. This variation is much more knee dominant compared to all other common variations of the deadlift.

Hack Lift

A hack lift is very similar to a conventional deadlift, except that the bar is behind your legs instead of in front. This makes the variation much more knee dominant. Below is a comparison of all four variations.


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Conventional Deadlift 𝝉𝝉 = 1000 𝑁𝑁 ∗ 0.4571 𝑚𝑚 𝝉𝝉 = 457.1 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 𝑛𝑛/𝑎𝑎

Hex Bar Deadlift 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.3017 𝑚𝑚 𝝉𝝉𝑯𝑯 = 301.7 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.1191 𝑚𝑚 𝝉𝝉𝑲𝑲 = 119.1 𝑁𝑁𝑁𝑁


Sumo Deadlift 𝝉𝝉 = 1000 𝑁𝑁 ∗ 0.3307 𝑚𝑚 𝝉𝝉 = 330.7 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 𝑛𝑛/𝑎𝑎

Hack Lift 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.2108 𝑚𝑚 𝝉𝝉𝑯𝑯 = 210.8 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.2096 𝑚𝑚 𝝉𝝉𝑲𝑲 = 209.6 𝑁𝑁𝑁𝑁

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Common “Dysfunctions” Knee Valgus

Knee valgus occurs when someone’s knees “collapse” inwards toward one another. This condition can exist out of movement, and is referred to as genu valgum in those cases, but during movement, it can often be seen in the concentric portion of a squat or landing from a jump. Knee valgus is associated with ACL injuries and patellofemoral pain syndrome. The gluteus medius is a small muscle on the side of your hip that attaches to your illiotibial (IT) band, which attaches to the lateral aspect of your tibia. This muscle acts to abduct the hip and, when strengthened, may help prevent knee valgus. For more on knee valgus, check out Bret’s blog article on it.

Butt Wink

Butt wink occurs when one’s femur runs out of room during hip flexion and makes contact with the acetabulum. This contact induces posterior pelvic tilt and lumbar flexion, and is commonly seen in the bottom of a squat. For more on butt wink, check out Bret’s video on it.

Poor Ankle Mobility

The ability for someone to dorsiflex may affect how they squat, that is, not allowing that person’s knees to go forward enough which puts an immense amount of torque on their low back and may cause the person to go into butt wink sooner or have valgus collapse in order to compensate. Proper ankle dorsiflexion will allow for a more balanced distribution of torques, and these concepts are also discussed in Bret’s video on butt wink and article on knee valgus.


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Poor Core Stability As mentioned earlier, spinal rounding is not just affected by a weak core, it’s affected by hip and knee strength and is used as a compensatory mechanism. Blaming spinal rounding on a weak core is a common misconception. Below, one can see how just 15º of spinal rounding can shift torques in a front squat. If a lifter has weak quads, he or she will be tempted to round the upper back in the front squat in order to shift more torque to the hips.

However, if one does need to increase their core stability, they can do so by bracing the abdominals/obliques. This will increase intra-abdominal pressure, which will increase spinal stability. The downside of this is that it increases spinal compression and your spinal erectors must produce more torque in order to counteract the spinal flexion moments provided by your abdominals, and this may lead to greater fatigue.

Front Squat 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.1414 𝑚𝑚 𝝉𝝉𝑯𝑯 = 141.4 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.2829 𝑚𝑚 𝝉𝝉𝑲𝑲 = 282.9 𝑁𝑁𝑁𝑁


Roundback Front Squat 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.21215 𝑚𝑚 𝝉𝝉𝑯𝑯 = 212.15 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.21215 𝑚𝑚 𝝉𝝉𝑲𝑲 = 212.15 𝑁𝑁𝑁𝑁

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Dorsiflexion Aids in the Squat Because dorsiflexion mobility is an issue for many lifters, there are external methods to help compensate for a small ankle range of motion. These include everything from placing a plate under someone’s heels to wearing Olympic lifting shoes. These methods, as seen below, make someone’s starting position in slight plantar flexion, which in turn gives them a greater range of motion before they reach their true dorsiflexion limit. This concept is better understood by looking at the free diagrams below, assuming the dorsiflexion aid puts the lifter in 10º plantar flexion, this dorsiflexion aid can change the moment arms from a 2:1 to nearly 1:1 ratio, thus balancing out hip and knee torques.

Back Squat 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.2829 𝑚𝑚 𝝉𝝉𝑯𝑯 = 282.9 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.1414 𝑚𝑚 𝝉𝝉𝑲𝑲 = 141.4 𝑁𝑁𝑁𝑁 2 x 4: Maximum Strength

Back Squat with Oly Shoes 𝝉𝝉𝑯𝑯 = 1000 𝑁𝑁 ∗ 0.2131 𝑚𝑚 𝝉𝝉𝑯𝑯 = 213.1 𝑁𝑁𝑁𝑁 𝝉𝝉𝑲𝑲 = 1000 𝑁𝑁 ∗ 0.2112 𝑚𝑚 𝝉𝝉𝑲𝑲 = 211.2 𝑁𝑁𝑁𝑁

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Belts and Intra-Abdominal Pressure As discussed earlier, IAP helps maintain a stable spine, but the addition of a belt will enhance that effect by creating more intra-abdominal pressure. This is most likely due to the rigidity of a belt (a bottle) compared to the rigidity of your muscles and connective tissue (a balloon). Because of the elastic qualities of connective tissue, it will expand like a balloon with some resistance. A belt, on the other hand, will not give way, thus limiting the amount of volume in your abdominal cavity. Boyle’s law states that there is an inverse relationship between volume and pressure, and this explains why a tight belt will increase IAP.


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Knee Wraps, Suits, Briefs, and Torque By wearing what is often referred to as “gear” in powerlifting, one can shift their strength curves, and therefore torque curves to become more even. This works by giving the lifter assistance where they are weakest but, after that tension from the “gear” is gone, the lifter must use their own strength to finish the lift. For example, with knee wraps, elastic tension is added to the knee to help the lifter “spring” out of the hole in a squat. Once the lifter has taken advantage of this elasticity, he or she must finish the lift with his or her own strength. In the graph below, the black line represents the standard torque curve and the red line represents the torque curve with “gear”. Hip Exte nsion Torq ue (Nm)

Hip Angle (º)


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Theoretical Effects of Support Gear Olympic Shoes Mainly used for front squats or Olympic squats. Allows lifter to stay more upright which decreases spinal torques and shifts the demand more to the knee joint. A lifter with strong knees but poor ankle dorsiflexion rounds his low back when he squats. Using Olympic shoes enables him to squat deeper while keeping his back upright, leading to greater forward knee migration and knee extension torque.

Knee Wraps Mainly used in geared powerlifting during squats. Provides passive knee extension torque, especially during deep knee flexion.

A lifter can produce 300 Nm of active knee extension torque at the bottom of a squat. With knee wraps, he may be able to produce 350 Nm of total torque.

Briefs/Squat Suit Mainly used in geared powerlifting during squats. Provides passive hip extension torque, especially during deep hip flexion.

Belt Mainly used for squats and deadlifts.

A lifter can produce 400 Nm of active hip extension torque at the bottom of a squat. With a briefs and a squat suit, he may be able to produce 500 Nm of total torque.

A lifter can produce 200 mmHg of IAP during the squat exercise. Wearing a belt, the lifter can produce 230 mmHg, which further stabilizes the spine.

Enables the lifter to produce greater intra-abdominal pressure during the squat exercise.

These seemingly minor aids combine to produce large increases in the total poundages that a lifter can hoist.


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Dynamic Effort and Muscle Activation Dynamic effort is a method of training popularized by Louie Simmons from Westside Barbell. Many lifters swear by the dynamic effort method and have noticed marked strength gains once implementing it. One major benefit of dynamic effort training is that it is not as taxing on the CNS and can be performed more frequently compared to heavier lifting. However, one pitfall with dynamic effort is that at the bottom range of motion, you will accelerate the load, but one must slow down as he approaches the end range of motion to prevent jarring forces from occurring associated with ballistics. Therefore, muscle activation decreases to decelerate the bar at end range of motion. To counter this decrease in muscle activation and increase the acceleration phase of the lift, bands and chains can be used as accommodating resistance. Even a small amount of accommodating resistance goes a long way in this regard.

Bands, Chains, and Torque

Bands and chains work similarly to the way powerlifting “gear” works in that they alter the strength and torque-angle curves, but the way in which they do it works a little bit differently. Bands and chains are often used to add resistance towards the top of a lift, or when a lifter is strongest. So, instead of decreasing the resistance in the beginning of a lift like “gear,” bands and chains increase the resistance toward the end of the lift to help even out the torque curve. A graph of this can be seen below, where the black line represents a standard torque curve, and the red line represents the torque with accommodating resistance.

Hip Extension Torque (Nm)

Hip Angle (º)


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Assistance Lifts Numerous, non-conventional lifts exist that may help one achieve more success with more traditional compound lifts. Some important ones will be discussed, along with their applicability to training and how they are carried over to other lifts.

Muscle Length Compared to Anatomical Position at Peak Hip Extension Torque Glutes Hamstrings Vastis Squat Lengthened Unchanged Lengthened Deadlift/Good Morning Lengthened Lengthened Slightly Lengthened Hip Thrust Unchanged Shortened Lengthened Back Extension Unchanged Unchanged Unchanged 45º Hyper Slightly Lengthened Slightly Lengthened Unchanged


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Hip Thrust

The hip thrust, popularized by Bret Contreras, is an exercise in which the lifter places their feet on the ground, upper back on a bench, and bar over their hips, and thrusts the bar forward. EMG data shows this to be the most constructive exercise for gluteus maximus activation, which would not only help hypertrophy the glutes, but also strengthen them. Implications of stronger glutes include a stronger squat if hip extension is a bottleneck and the lockout in the deadlift. The gluteus maximus has also been shown to be the strongest stabilizer of the sacroiliac joint (SIJ) (Barker et al., 2013). The activation patterns of the hip thrust jive very well with the findings of Worrell et al. (2001), i.e., the gluteus maximus has the highest EMG activity at end range. Because the force from the load is always perpendicular to the hips, resisting extension, one is able to maximize hip extension torque and gluteal EMG activity. Below is a graph of the hip extension torque in a hip thrust of a 6’4, 100kg male using a 220kg load.

Back Extension on GHD

Somewhat of a misnomer, the back extension is really a hip extension exercise. Because the legs are straight during the back extension, this exercise would elicit more hamstrings and, because the back is held in a neutral position, the spinal erectors are working isometrically to stabilize the spine. The gluteus maximus and hamstrings share the hip extension torque. The movement can be performed on a glute ham developer. The most challenging position in the back extension is at full lockout where the torso is fully extended.

45º Hyper

The 45º Hyper is a piece of equipment on which the back extension is often performed. The torques when performing a back extension on the 45º Hyper are on the graph and show an inverted u-shaped curve, with the most challenging portion in the middle of the lift. 2 x 4: Maximum Strength

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Good Morning

A good morning is performed similarly to a stiff leg deadlift, but instead of the bar being held in one’s hands, it is placed on the back – similarly to a back squat. This movement elicits similar EMG activity as the stiff leg deadlift, that is, hamstrings and glutes contributing to hip extension and the spinal erectors acting isometrically to maintain a neutral spine. The torques necessary to complete a good morning are shown on the graph and show that the most challenging portion is a the bottom of the movement when the hips are fully flexed.

More information on these concepts, horizontal back extension, 45º hyper, and good mornings are discussed further by Contreras et al. (2013). Bret was also nice enough to record a video summarizing the article and these concepts.

Contreras, B. M., Cronin, J. B., Schoenfeld, B. J., Nates, R. J., & Sonmez, G. T. (2013). Are All Hip Extension Exercises Created Equal?. Strength & Conditioning Journal, 35(2), 17-22.

Reverse Hyper

The reverse hyper was popularized by Louie Simmons at Westside Barbell and is a great movement for learning how to control one’s pelvis and lumbar spine during a hip hinge while properly utilizing the glutes. The reverse hyper is performed by laying one’s upper body face down on a surface with the legs hanging off, secured to a pendulum via a strap. The lifter will simply move in and out of hip flexion while controlling the movement with their hip extensors. It should be noted that on the graph below, we are assuming a quasistatic model, i.e., there is no momentum and that the lifter is not actively preventing the weight from swinging past 90º of hip flexion.

Below is a graph showing the torque-angle curves of the previous four exercises if a 6’, 200 lb subject were to hold a 100 lb weight at the top of his or her chest.

Hip Extension Torque (Nm)

Hip Extension Exercise Torque-Angle Curves

600 500

Good Morning

400

45º Back extension

300 200 100 0

90º


135º Hip Angle

180º

Horizontal Back Extension Reverse Hyper

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Glute Ham Raise

Just like the name says, the GHR is an excellent movement for the development of one’s hamstrings, but as far as the glutes go, it is a bit of a misnomer. This is due to the fact that knee flexion is the bottleneck: one has a much higher capacity for hip extension torque than knee flexion torque, but the GHR puts a lot more torque on the knees than it does the hips. It is performed on a glute ham developer (GHD) by extending at the knees and flexing at the hips until the body forms an L shape. Once at the bottom, the lifter simply extends at the hips and flexes at the knees.

Glute Ham Raise Torque-Angle Curves

Torque (Nm)

600 500 400 300 200 100

0

Knee: 180º Hip: 90º


Hip Extension Torque




Knee Flexion Torque

As you can see, the GHR is a knee dominant (knee flexion) exercise and not a hip dominant exercise. For more information on the Glute Ham Raise, check out Bret’s article on T-Nation, Gutting the GHR. Barker, P. J., Hapuarachchi, K. S., Ross, J. A., Sambaiew, E., Ranger, T. A., & Briggs, C. A. (2013). Anatomy and biomechanics of gluteus maximus and the thoracolumbar fascia at the sacroiliac joint. Clinical Anatomy.


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Biomechanics of the Squat and Deadlift

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