A Biomechanical Analysis of the Squat: How Bar Position Affects the Movement

Written by: Kevin Cann

The terms “hip dominant” and “knee dominant” squats get thrown around quite a bit. I use these terms frequently myself. Often times people will alter the bar position on the body to attempt to get a different training effect.

For example, we may high bar squat, or front squat instead of using a low bar position to get more quad work in our squat. The idea is that if we move the bar 2-3 inches higher on our back to the top of our traps that we will have a more positive shin angle (knees tracking further over the toes) and we will get more quad work out of the exercise. A front squat places the bar in front of the body and would lead to a greater shin angle than a high bar squat.

Low Bar Position and Squat

High Bar Position/Squat

Front Rack Position/Squat

The problem with this is it is not the case. All squat variations have very similar muscle activity (1). No matter what the shin angle or bar position is in the squat, the muscle activity for the quads is the same (2). The reason for this is the co-contraction of the hamstrings.

The hamstrings are a biarticulate muscle group, meaning that they cross two joints. The hamstrings attach at the hip and also the knee. Due to them crossing two joints, they can act upon two joints. Not only do they extend the hips, but they also flex the knee.

During the concentric portion of the squat we are trying to extend the knee. The quads are our primary knee extensor muscle group. When we have a more positive shin angle we increase the moment arm for the knee extensors, that part is true. This is where logic tells us that it is a more quad dominant squat.

However, if we sit back into the squat and make it more hip dominant, we get a smaller moment arm for the knee extensors, but they have to fight the co-contraction of the hamstrings harder. This is why the muscle activity for the quads is the same for all shin angles. They are either fighting the weight on the bar, or fighting the hamstrings.

The body will attempt to use monoarticulate muscles first. This means that the glutes should be our primary hip extensors in the squat, with the quads extending the knee. There are no negatives associated to the glutes extending the hip. If the hamstrings take over for the glutes, there is a cost associated with it because they are trying to bend the knee as well.

We want the hamstrings to kick in at the sticking point of the lift. By this point some knee extension should be achieved, which gives the quads greater leverage to extend the knee, making the hamstring contraction less of a problem for the quads.

Often times we will see a breakdown in the lift where we get the knees extending somewhat, hips shifting further back, and the chest pitching forward out of the hole. This is our body shifting the load to our hamstrings, glutes, and back. This is not as ideal as it may sound.

Example of a “good morning” squat

To lift big weights you need to stay as upright as possible in the squat. Having the torso fall forward puts the weight of the bar in front of our center of gravity, making it very difficult to lift. We want the bar to be over our midfoot at all times (right over our center of gravity).

When this technique fault occurs we also get a lot of body movement with very little bar movement. This is wasted energy and will result in less weight being lifted. When this technique fault occurs often times we chalk it up to weak quads.

This absolutely could be the case. Quads get maxed out and shift the hips back and chest forward, which allows us to get some knee extension without having to fight the weight of the bar. From there it is up to the glutes, hamstrings, and back to fight through the tough position. This is your body giving you the best chance to stand up with the weight.

I am not arguing that weak quads are a culprit here. However, I do not think it is the definite culprit. Remember, the quads are not the only muscle group helping us stand up from the squat. The glutes also play a major role. If the glutes are weak, this pattern also makes sense.

It is true that when we shift the hips back we are increasing the moment arms for hip extension, but we are also increasing the musculature involved. Often times people’s hamstrings are better hip extensors than their glutes. This is probably due to the increasingly sedentary lives we lead. When we shift the hips back we are increasing moment arms of the hip extensors, but we are possibly shifting it to the stronger hamstrings.

This would explain why beginners tend to have this movement pattern in the squat, even unloaded at times. Often times these beginners will have overdeveloped quads when compared to the hamstrings as well. I find it hard to believe that their quads are too weak to handle an unloaded or minimally loaded squat. However, I do reserve the right to be wrong here.

The goal to lifting bigger weight is fighting that torso lean as much as possible. If that is the case, and shin angle does not affect the muscles involved, then why can people typically lift more with a low bar squat than a high bar position or a front squat?

The one main difference between all of these bar positions is obviously where the bar is positioned on your body. The lower the bar is on our back, the shorter our torso is for the lift. This means a smaller moment arm for our thoracic extensors. Placing the bar lower on the back decreases the requirement of our back muscles within the lift.

Weightlifters have very strong thoracic extensors, and this may explain why they can lift very heavy squats in a high bar position. One of my past clients was a weightlifter that also had an almost 4 times bodyweight deadlift. Her squat was very weak compared to the competitive lifters in her class, but her pull was one of the best.

She got pitched forward very easily in the squat, so using a high bar position was beneficial for her at the time. This allowed her to stay as upright as possible, and her squat numbers were nowhere near challenging enough for her thoracic extensors. This was the fastest route to a bigger squat when a national championship meet was approaching. But as her squat numbers increase, she will need to lower the bar on her back.

With that said, there are many great squatters that train mostly with the high bar squat. I remember Fred Hatfield saying that he primarily trained with a high bar squat in training. This helps strengthen the back muscles, while muscle activation is the same, and it tends to be safer for the elbows, as low bar squatting is a major culprit of elbow pain.

Even if you train in a high bar position at some point the weight will become too heavy for your quads and you will run into the same technical fault that we discussed earlier. The goal is to continually make yourself stronger so that these faults happen with heavier weights.

You need to find which squat variation fits you best. If you are a competitive powerlifter, you should probably squat low bar. However, if you are just using the squat to get stronger, find which position is most comfortable for you.

If you have ever had knee issues, I would suggest squatting with the more “hip dominant” squat. This may mean low bar and sitting back a bit more. Squatting with a greater shin angle places more shear force on the knee joint. Limiting this with knee issues would be smart.

However, a greater forward lean places greater sheer force on the spine. If you have back issues, you may do better with a high bar squat or front squat. I have also found that people having pinching in the front of their hips also do better with a low bar squat and sitting back more into the squat, as the glutes and hamstrings help pull the femur back in the hip joint.

If your elbows hurt from squatting with the bar lower on your back, raise it up just a hair. Often times this small amount of bar placement changes makes all the difference in the world for comfort. This would place the bar between a high bar and low bar position.

This article may sound like I am saying that the hamstrings are not important. They absolutely are. They are very important for the deadlift. They are also very important to preventing ACL and other knee injuries in field and court athletes. All I am saying is they may not be a culprit in your squat issues.

When we squat our knee angle does not alter muscle activation. Our glutes should extend the hips, while the quads extend the knee. The hamstrings should primarily be used to transfer force from the hip to the knee, and aid in hip extension when we hit the sticking point and have already achieved some knee extension. Makes sure your quads are strong, your glutes are strong, and you are fighting to keep your torso as upright as possible while maintaining the bar position over your midfoot.

from The Paleo Diet http://ift.tt/2hx9bbS