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The Physics of Lifting: Don’t Forget to Hinge

Deadlifts, low-bar back squats, and kettlebell swings are a great way to utilize the posterior chain.

Craig Marker

Written by Last updated on Nov 22, 2021

If your program contains many front squats, Olympic movements, and wall balls, you might want to add in low-bar back squats and hinge movements to stay balanced.

The front squat and its variants emphasize the anterior (thigh) muscles, while the low-bar back squat and hinge movements (deadlift, kettlebell swing) emphasize more of the posterior (hamstrings, glutes) muscles. Let’s take a look at why this happens and what exercises you need to keep yourself balanced.

Bar Position Determines Hip Angle

In any movement, the weight is pulled down by gravity in a straight-line path to the ground. Our bodies move around this path. For example, when we get up from a sitting position, we lean forward to counterbalance the weight in our hips (try to stand from a sitting position without bending forward; it is harder than you think). So, any time we add weight to our body, we balance it out along this imaginary line to the ground.

Any time we add weight to our body, we balance it out along this line to the ground.

In the front squat, we keep an upright torso, as that keeps the weight following our imaginary line to the ground. In a low-bar back squat, we bend forward to keep the weight along this same line.

Mark Rippetoe in Starting Strength has a great discussion about angles and lever arms in the squat and deadlift.

What Muscles Work More?

Squats of any type will use many muscles in the legs. However, the angle of the back changes the emphasis of which muscles do the most work.

“Many CrossFit-style programs overemphasize thigh-dominant exercises, such as front squats (in the Olympic lifts) and wall balls.”

The most basic example is a stiff-legged deadlift or good morning. In this exercise, the legs remain stiff and the upper body bends at the hips. The glutes and hamstrings do most of the pulling to bring the upper body upright. Thus, this movement almost exclusively focuses on the posterior muscles.

At the other extreme, we have a leg extension machine. When using this machine, the knee goes from a bend until it is straightened. The thigh muscles are dominant and are used to pull the lower leg into the straightened position.

More Hip Hinge = More Glute/Hamstring Activation

Putting together the above information, we can see that:

  1. In the stiff-legged deadlift, our posterior muscles are levering our back upward in the movement. Low-bar back squats are going to use more of the posterior muscles, as this movement requires levering our back into the upright position.
  2. The higher the bar (or if it is in the front squat position), the less we need to lever our back, and we will have more thigh muscle involvement to straighten our leg (similar to the leg extension machine).
Muscles worked in the front squat and back squat

Summary

Many CrossFit-style programs overemphasize thigh-dominant exercises, such as front squats (in the Olympic lifts) and wall balls. So, remember to use hip hinge exercises as well to balance out the upright torso squat exercises. Deadlifts, low-bar back squats, and kettlebell swings are a great way to utilize the posterior chain.

Further Reading:

Photo 1 courtesy of CrossFit Impulse.

Photo 2 courtesy of Craig Marker.

Chart From Starting Strength, Copyright 2008, The Aasgaard Company. Used by permission.

Craig Marker

About Craig Marker

Craig Marker, Ph.D. CSCS, StrongFirst Senior Instructor, is a fitness enthusiast who has spent his life trying to help people improve their lives. He is an Associate Professor at Mercer University teaching psychology and research methods. He works with students on how best to understand research and place it into context. He has published over fifty articles on psychology and research methods. As a researcher, he understands the latest cutting-edge research on fat loss, muscle gain, sports performance, and nutrition.

As a psychologist, Craig has focused on research and treatment of anxiety disorders, which positions him to understand motivation and the fear of making life changes. His upcoming book, the AntiFragile Self, takes on the topic of building a stronger person in the mental and physical domains.

As a certified StrongFirst Kettlebell Instructor, Craig views kettlebells as one tool in the trade of forging a better person. He also has certifications in CrossFit, CrossFit Mobility, and CrossFit Gymnastics. He uses the Functional Movement Screen and multiple corrective movements to make sure his students are performing at their best for the rest of their lives. You can visit him in person at CrossFit Empirical in Fort Lauderdale, Florida.

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