The squat is one of the most fundamental and commonly performed exercises for strength gains, sports training, and rehabilitation. Many different variations of the squat are routinely prescribed in CrossFit workouts, and while the lower-body movement patterns of the front, back, overhead, and air squats might look the same, they each differ in degree and differentiation of total-body muscle recruitment. For the purpose of this post we will compare the front and back squats.

The back squat is performed with the bar resting on the upper trapezius and the posterior deltoid with the hands gripping the bar. The front squat is performed with the bar resting on the upper pectoralis major just below the clavicle and the anterior deltoid using a loose finger grip to secure the bar just outside of the shoulders; with the arms rotated forward so the elbows are pointing forward, and the upper-arm parallel to the ground. Other than the bar and arm positions, the exercises should ultimately be performed the same way by keeping the weight in the heels, maintaining proper lumbar curve, keeping the hips back and down, eccentrically decelerating down to point that the hip crease is below the knee, tracking the knees over the feet, and then concentrically accelerating back to full extension at the knees and hips.

The squat is generally considered as a Quadriceps exercise in the fitness industry, but limiting the exercise in this way undervalues what it accomplishes if performed correctly. In addition to the quads, the squat recruits and activates the gluteals, the hamstrings, stabilizers of the lower leg, and the core musculature including the abdominals and muscles of the back.

Interestingly, if both variations of the squat are performed with good form, the muscle recruitment and activity are almost identical with only minor variations. However, there are many factors that may influence the exercise, both decreasing efficiency and increasing the risk of injury. These factors include, but are not limited to: not maintaining proper lumbar curve, not tracking the knee over the foot, keeping the weight on the ball of the foot, or not getting the hips back far enough causing the knees to cross the plane of the toes.

Flexibility also plays an integral role in proper squat mechanics. For example, over-active hip flexors may rotate the pelvis forward causing the torso to fall forward, and put more pressure on lumbar vertebrae. If there is not full range of motion at the shoulder, the arms cannot be rotated forward making it easier for the torso to fall forward.

That being said, if there are no barriers to good form, there are a few differences that are observed both quantitatively through EMG data, and qualitatively through biomechanical movement observation. The back squat recruits more Hamstring activity, specifically the Biceps Femoris and Semitendinosus. The back squat also recruits less Quadriceps activity. Other than the minor differences of the lower body, the only other difference in regard to muscle activity is that the front squat requires more stability and therefore the muscles of the lower-back, specifically the Erector Spinae, are much more active in the front squat in order to keep the torso upright throughout the complete movement.

Aside from muscle activation, the other major factor that we need to look at is the potential for injury. During the squat this can most effectively be looked at through the forces that are acting on the joints throughout the movement of the exercise. The forces in regard to the squat are focused primarily on the knee and are compression and shear. (Keep in mind that these forces being discussed are when the exercises are performed correctly. If they are performed incorrectly, then other forces like torque come into play, and compression and shear are both increased, substantially increasing the risk of injury.) Compressive forces are significantly greater during the back squat than the front squat; shear forces are very similar in both squat variations. Both compression and shear are low in comparison isolated, open-chain leg exercises like the leg extension and leg curl machine. While compressive forces are found to be less in the front squat, it may be due to the fact that people front squat less weight than the back squat, and not that it is biomechanically more efficient.

In conclusion, there are few relatively small differences between the back and front squat. However the front squat requires more flexibility and skill to perform correctly, and puts less stress on the joints. So a person will achieve more in progressive strength and flexibility from front squatting, which is what CrossFit training strives to accomplish, getting the most out of every rep, of every exercise.


The nature of CrossFit is inherently competitive. It’s one of the reasons that people keep coming back; but it also tempts some to push more than they should. This may lead to overtraining, and in some cases, injury, or what I like to call “pre-injury.” Injuries are usually structural and prevent continuation of the activity, while “pre-injury” causes pain and immobility enough that the person definitely feels it the next day, but are able to return within a matter of days, instead of weeks or months.

The potential for injury is also greater within CrossFit because of the focus on “prescribed” workouts. Many CrossFitters’ pride forces them to perform workouts as prescribed before their individual strength and endurance progression would allow. CrossFit-style programming usually, but not in all cases, does not spend adequate time with stability training and/or proper form. Most CrossFit injuries and pre-injuries deal with the back, and the majority of those can be traced directly back to those two factors of stability and form.

Deep within the core musculature is a muscle called the Quadratus Lumborum, more commonly referred to as the QL. The QL connects the anterior crest of the ilium to the medial (closest to the spine) half of the bottom rib and the transverse processes of upper four lumbar vertebrae. While relatively small, the QL is by no means insignificant. The Quadratus Lumborum is directly linked, and in many cases, responsible for nearly all cases of low back pain.

The QL primarily works ipsilaterally for flexion of the spine (side to side bending), and QL is considered the primary stabilizer in the frontal plane, but more importantly for our discussion as it relates to CrossFit, the QL can work bilaterally to extend the spine, by picking of the slack of the Erector Spinae muscles if they are weak or inhibited.

There are a couple of scenarios in which the QL may be responsible for low-back injuries in CrossFit. The first is if the QL itself is under developed, and the second is the need for the QL to overcompensate for weak or inhibited Erector Spinae and/or Multifidus muscles. Many times it’s a combination of both.

There are not many, in fact I can’t think of any on the top of my head, CrossFit exercises or skill that involve lateral flexion of the spine which is the QL’s primary movment, but there is no shortage of CrossFit exercises that require solid frontal plane stability. Frontal plane stability is characterized by being able to maintain body balance without losing balance forward or backward. Any exercise where a load is raised above the head requires frontal plane stability. The longer the weight is held above the head, and degree of movement progressively increases the need for balance. For example, one may be able to push 95 pounds above the head for a “thruster” easily in comparison to a “snatch.” The “snatch” may be easy in comparison to the “overhead squat.” The QL is primarily responsible for the ability to retain stability throughout the movement. If the QL is weak or underdeveloped, if the load is increased, the pelvis rotates forward putting added stress on the lower back causing pain and/or mechanical injury.

In the case where the other muscles of the lower back and hips are weak or otherwise inhibited, the QL must act synergistically for movement. If the QL uses its limited energy to assist in this way, it will fatigue quickly and will  lose its ability to stabilize the body in the frontal plane.

To decrease the chance of low-back pain and/or injury, every CrossFitter should work progressively to increase the strength and flexibililty of the Erector Spinae, Multifidus, and Quadratus Lumborum. In addition, QL exercises should be incorporated into every dynamic warmup for any workout that requires frontal plane stability. Doing this will essentially “wake up” the muscle if it is/has been inhibited though inactivity. My favorite three exercises to increase QL strength and stability are: 1) side plank with hip raise; 2) side bends with kettlebells, dumbbells, or bands; 3) hanging side to side swings.

If we consciously program to strengthen our stabilizers, specifically the QL, and not let our pride put so much emphasis on “rx” then we will significantly decrease the risk of low-back pain and injury, and we can continue to feed our CrossFit addiction

What exactly is full range of motion? We hear the term all the time as one of the key foundational components of CrossFit training and conditioning, but what is it? Who, or what, sets the standard of what full range of motion is? And more importantly, why is it so important? Every joint of the body is biomechanically designed to move in certain directions, and the range of motion is distance and direction of the movement of that joint. The mobility of a joint is limited by a number of factors including, but not limited to: the ends of bones, amount of fat around the joint, and most importantly for our discussion and the CrossFit community, is the elasticity and/or flexibility of the connective tissues (muscles, tendons, ligaments) associated with the joint.  My definition of Mobility has to deal with a combination of flexibility, strength, and proper technique in performing an exercise. A weakness in any one of these components may negatively affect mobility and performance. That then, is my answer to the question posed in the first paragraph. The appropriate range of motion is determined by what is required to perform the exercise correctly and safely.  We all know that strength is the most common limiting factor in beginning CrossFitters. It is also the factor that most CrossFitters care the most about. However, my contention is that the other two limiting factors, flexibility and technique, while not as exciting, play a more important role in the longevity and progression of every individuals CrossFit experience.  Let’s use the “thruster” to discuss this idea. When a CrossFitter is unable to perform a prescribed thruster, the exercise is modified by decreasing the weight. It’s commonly accepted that the modification is due to a lack of strength. It is usually not that simple. That same person might be able to perform different, isolated exercises at the same or even greater weight than the thruster, displaying that they have sufficient strength. So what gives? If the lack of strength is not the culprit, what is? The thruster is a technical exercise to perform. Essentially it combines a front squat and push press. Each exercise requires technique in itself and the transition between the two can pose problems as well. Some technique points include: keeping the weight in the heels, hips back and lower than the knee at the bottom of the movement, holding the bar racked against the chest and keeping the elbows forward throughout the front squat portion of the movement, pulling under the bar and locking out overhead, etc.  As we break down each technique point individually, we find that flexibility, or lack thereof, is the single greatest determining factor of efficiency of the movement. For example, those with tight calves and hamstrings find it difficult to keep the weight in the heels. When they come up on the balls of the feet, there is a loss of stability as the calf muscles are required to support the weight. Those that spend a lot of time sitting usually have tight hip flexors and IT bands. Tight IT bands decrease the knees’ ability to track straight and force them progressively inward as the knees bend. Tight hip flexors cause the pelvis to rotate forward putting added stress on the lumbar vertebrae and pull the trunk forward pulling the weight in front of where the center of gravity should be.  One of the most common technique issues is not being able to point the elbows forward and being able to hold them forward during the squat. This inability is usually caused by overactive or tight Latissimus Dorsi muscles on the back and when coupled with tight hip flexors makes it very difficult to perform without undue risk of injury to the Crossfitter. I know that we are eager to PR our workouts, and because of that we focus on time and weight. But if we refocus, and systematically approach increasing flexibility through a combination of dynamically warming up, and stretching using a combination of static, ballistic, PNF, and myo-fascial release with a foam roller, we will ultimately improve faster and more safely.

Last week, I was on round 4 of the workout “Nancy” (5 RFT couplet of 400m run and 15 overhead squats) when I noticed my left hand, specifically my thumb, felt like it was “asleep.” I figured it was a circulation issue caused by the wrist straps I was wearing. I took the straps off and finished the WOD. Surprisingly to me, I still had the “dead-arm” feeling in the top of my forearm and thumb, which continued throughout the rest of the day. Because of my background in Human Movement Science, I wanted to figure out what was going on.

I found that my symptoms were caused by the compression and impingement of nerve root C6 at which is located on the side and back of the lower portion of the neck. Root compression and impingement is usually initiated by disc herniation, but can in some circumstances be caused by sudden stretching and/or compression.

The snatch-balance movement that I was using to set up my overhead-squats, was most likely the culprit of the sudden compressive force that caused the nerve root to be compressed. However, upon further evaluation, I believe it may have had more to do with poor lift mechanics on my part.

When performing the overhead squat, the arms are elevated at the shoulder (gleno-humeral) joint, and the shoulder blades are retracted, and slightly elevated and upward rotated. This position in itself does not compress nerve root C6, but if the person performing the exercise extends (tilts head upward) and protracts (forward head position) the neck , as I was, the combination of the shoulder and neck movements puts excessive compression on the nerve root, causing radiating, pain and numbness through the top of the forearm and thumb.

After tracing my symptoms to C6, I performed some neck stretches did some myo-fascial release on my Trapezius and Levator Scapulae, the radiating pain and numbness disappeared.  After, the pain was gone, I wanted to test my hypothesis; I elevated my arms, protracted and upward rotated my shoulders. I felt nothing. I pushed my head forward and slowly looked up. As if on cue I started to feel the nervous tingling in my thumb.

While nerve root compression and impingement may cause temporary discomfort, if the incorrect movement patterns are not corrected, chronic injury and herniation may occur and cause more significant and long term problems.

I decided to start a blog to provide information and ideas about the functional movement efficiency of CrossFit exercises and skills. I am a long time trainer and fitness professional in the field of biomechanics and human movement, but am relatively new to CrossFit.

As a new CrossFitter, there have been many times when a movement just didn’t feel right, or may have been painful or awkward.

It will be my attempt to provide information that may be helpful to fellow CrossFitters to decrease the risk of injuries, provide tips to increase mobility, flexibility, and strength.

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Posted: March 23, 2012 in Uncategorized

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