Body Leverages and Force Production

How does your body create movement?

In the previous topic we discussed briefly how your body uses muscular stretching and contractions to create movement. In this topic we’re going to expand on that to describe the squat lifting pattern.

We are going to do this by breaking the body down into segments and discuss which muscular systems you use on them when you squat, as well as the forces exerted against them. In the next lesson we will expand on this information, describing how to adjust your squat pattern for maximum power.

The Spine

Function

Many of you don’t think too much about the spine’s function in the squat. You may just think about it as something you pray you don’t injure when you step under your first ungodly heavy weight. The spine, however, plays a significant role in your squat – your spine transfers power directly from your legs to the loaded bar. How effectively you prepare yourself to transfer that power plays a pivotal role, not only in how effectively you squat, but also in your resistance to injury.

Joint(s)

The joints we are concerned here are between each of the 24 vertebrae in your spine. Optimally the spine acts as a static lever while you squat. The function of the spine is to simply transfer power from your legs to the weight, you want to brace your spine so that there is minimal movement, if any, between the vertebrae in your spine. Keeping your spine stable throughout the squat is discussed in the next topic, Blocking and Bracing.

Muscular System

There are three muscular systems engaged to maintain spinal stability as you squat:

• Upper Back: The major muscles of upper back consists of your traps, lats, and rhomboids. You’ll engage the muscles of the upper back to stabilize the thoracic region of your spine while you squat.
• Spinal Erectors: Your spinal erectors are a group of muscles that connect to the top of the pelvis and ribs, and to your vertebrae along its entire length. They assist in maintaining spinal stability along the entire length of your back.
• Abdominals: Your abs help you maintain core stability, and during a heavy squat are used when bracing to create intra-abdominal pressure, which stabilizes the lumbar portion of your back.

Mobility Considerations

While you work to keep the spine itself immobile during the squat, there are mobility concerns to keep in mind to lift heavy and remain healthy.

• Shoulder Mobility: To squat effectively, you need sufficient mobility in your shoulders to wedge yourself under the bar and pull your scapula in and down to create thoracic stability. Insufficient mobility in your shoulders can lead to a great deal of shoulder and elbow pain. It can also impact your thoracic and overall stability.
• Hip Mobility: Lack of hip mobility may cause your hips to rotate to the posterior at the bottom of the squat, resulting in lumbar flexion (commonly called the ‘butt wink’). This can increase the risk of injury under heavy loads.

The Hips

Function

When squatting for power, your hips play a pivotal role. You need the mobility in your hips to reach depth, and once there a strong hip drive extends your hips powerfully, forcing the bar back up (assuming your back is braced solidly providing an effective conduit to transfer your power to the bar) and completes the lift.

Joint

The hip joint is one of the most dynamic joints in the body. It is a ball and socket joint and moves in about every dimension possible:

• Flexion/Extension: Flexion and extension at your hips is, of course, the most significant movement at the hips during the squats. As illustrated below, your hips are in flexion as you descend and your hips and thighs move towards each other. Hip extension occurs as you come back up, with your torso and thighs moving apart until you stand up straight again.
• Abduction/Adduction: Hip abduction occurs when you spread your legs apart, adduction is the act of bringing them back together. You will have abduction as you move into your squat stance, but during the squat there should be little to no abduction or adduction. With a solid squat rep, your knees should track in the direction of your toes throughout the full range of motion down and back up.
• Rotation: You also have a limited amount of rotation of your thigh at the hip. External rotation occurs as you rotate your thigh outward, think about turning your toes outward. Internal rotation occurs when rotate your thigh (and toes) inward. Rotation is an oft overlooked component of the squat. As with abduction/adduction, with good squat technique there should be limited rotation, either internal or external.

Muscular Systems

• Quads: Three of the four quad muscles are concerned solely with knee extension (straightening, see below). The fourth (the rectus femorus) performs knee extension and hip flexion. For the purpose of a power squat, the quadriceps have a greater role as a stabilizer than a source of squat power. The quads are important in maintaining your hip/back angle as your glutes and hamstrings drive you up out of the hole.
• Hamstrings: Your hamstrings have a role in both hip extension and knee flexion. For the purpose of the squat, their primary role is to extend the hips and drive you upwards. Noteworthy, is that since they cross both the hip and the knee joint, increased knee flexion has the tendency to loosen tension on the hamstrings. Where this becomes important is at the bottom of the squat. You often will see a novice squatter allow their knees to shift forward as they hit maximum depth. This causes the knees to flex more, releasing tension on the hamstring, and reducing stability and rebound off the bottom of the squat.
• Adductor Magnus: As the name implies, the Adductor Magnus’s primary role is adduction (bringing your legs back together). It is, however, also a powerful hip extensor. Personal theory: having strong adductors heavily involved in your squat without balancing abductors can cause your knees to cave in as you come up – that is, after all, adduction. What a fortuitous time to discuss the Gluteus Medius.
• Gluteus Medius: The Gluteus Medius role is in abduction and external rotation at the hip. In a heavy squat the Gluteus Medius is an important stabilizer. It is one of the most important muscles in addressing issues with your knees caving in. Personal theory: the abduction/external rotation role of the Gluteus Medius balances the adduction aspect of the Adductor Magnus, allowing the adductor to more effectively contribute to hip extension.
• Gluteus Maximus: I did save the Gluteus Maximus for last on purpose. It is the largest muscle in the body (unless you’re a marathon runner), and the most powerful hip extensor muscle. As you’ll see in coming lessons on squat mechanics, because of your glutes’ great strength, adjusting your squat mechanics to maximize the glute…maximus involvement will greatly increase your squat’s power.

Note that not only does hip extension use one of the largest and strongest muscle in the body, the Gluteus Maximus, a large number of powerful muscle groups are engaged to perform hip extension. This is a very good reason to use lifting technique that is hip dominant when squatting for power.

Mobility Considerations

To squat effectively, you need hip mobility in all three dimensions: flexion/extension, abduction/adduction, and internal and external rotation. To keep things simple, let’s test your hip mobility using a body weight squat, and a plyo box that has you below parallel when you sit on it.

Squat to the box, maintaining the proper squat pattern, with your shoulders directly over the center of your feet. If you are unable to keep your back flat or slightly arched, or your knees cave inward while squatting to the box, you may need to test further to determine if hip mobility is the root cause of these issues. You might try the Thomas Test for additional hip mobility assessment. You can find descriptions of the Thomas Test online.

Keep in mind that some people have physical hip structures that do not allow significant abduction and external rotation while squatting. I’ll touch on that a little in the later lesson addressing individual squat mechanics.

The Knee

Function

To maintain a proper squat pattern, your knees flex in relative balance with hip flexion as your hips descend. As they flex your knees will shift forward in the direction of your toes. The extent to which they travel forward is largely a function of your body mechanics.

As you ascend upwards, your knees will extend. In a proper squat they should extend evenly until you lock out. Locking your knees early, before your hips lock out, reduces your leg drive during the ascent.

Keep in mind, that while I don’t have a specific section here on the ankle joint, your ankle must also flex in relative balance with your knee flexion to maintain a balanced squat pattern.

Joint

As opposed to the hip joint, the knee is a relatively simple joint, flexing and extending in just one plane.

Flexion is simply bending the knee, and extension is straightening it.

In a well executed squat your knees should track in line with the direction of your toes through the full flexion and extension movements. Although knee valgus (caving inward) is not a function of the knee’s movement, it is an indication of a weakness that should be addressed for maximum squat effectiveness.

Muscular Systems

• Quads: Your quadriceps are powerful knee extensors. They are actively engaged stabilizing your knee joint as you descend. During your ascent they extend your knee in unison with your hip extension. Although with the power squat we work to maximize your glute involvement in the movement, your quads’ role remains significant.
• Hamstrings: As described above, the hamstrings’ primary role in your squat is to help extend your hips as you come up. The hamstrings, as an antagonist to the quads, also play a role in knee flexion. They do not have to actively flex the knee during the squat (the weight on your back will do that), but they do need to stay actively engaged to maintain stability as you descend. As noted above, allowing your knees to flex and shift forward suddenly once you hit parallel relaxes your hamstrings reducing their ability to extend your hips and your control of the weight. This limits the hamstrings’ effectiveness in extending your hips as you start your ascent.

Mobility Considerations

Knee mobility is largely a function of your quads. When your quads begin to tighten up they pull your patella out of position as the knees flex, resulting in knee pain as you squat. Often myofascial  release techniques, such as foam rolling or deep tissue massage, can return the quads to their full range of motion function. I have also found that dynamic warm-ups that give the quads a deep stretch, such as Bulgarian split squats, can significantly improve and maintain knee mobility.

Ankle

Function

Your ankles play a passive role in your squat. As you descend your knees shift forward with an even pattern throughout the ROM. To allow your knees to move forward, your ankles must also flex forward (plantar flexion).

Joint

The ankle is actually a quite dynamic joint. It allows movement in all directions. Using the knee as a reference point:

• Plantar Flexion: Occurs when the knees move forward. This is the movement we are most concerned with as you squat. When executed flawlessly, this should be the only ankle movement.
• Dorsiflexion: Occurs when your knees move backward from the midline of the foot.
• Inversion: Occurs when your knees move inward, towards each other.
• Eversion: Occurs when your knees move outward.

Mobility

To execute a proper squat, your ankles must have sufficient mobility for plantar flexion so that they allow the knees to move forward as you descend. The magnitude of this flexion is dependent on your individual body mechanics, but typically your knees will not travel forward past your toes. If you have insufficient plantar flexion mobility, your body will adjust, creating a dysfunction in your squat. For example, your knees may shift inward as you descend, resulting in ankle inversion. Your hips may also shift further backwards, resulting in a greater forward lean, possibly forcing the bar forward of your center of gravity.

A simple test of ankle mobility is to stand with your toes close to a wall and push your knees forward to see if you can reach the wall with them.