The Hack Squat: Benefits, Muscles Used, and More

published by: Debbie Luna
Last Updated:
June 7, 2022

The hack squat is a lower body compound movement best known for its highly effective focus on certain muscle groups responsible for the extension of the patellar joint, rivaling and even surpassing the capacity of the standard barbell squat.

The hack squat presents several advantages over many other lower body compound exercises - but must first be fully understood and performed in the proper manner so as to maximize the training stimulus and benefits received from its performance.

For the most part, the hack squat is a quadriceps femoris-dominant machine based resistance exercise with great usage of the hip and knee joints and a distinct lack of shear force or stress on the lower back; thereby making it an excellent exercise for individuals with a history of injury, or athletes seeking greater quads training stimulus.

What is the Hack Squat?

The hack squat, in a greater definition, is a machine based resistance exercise with a muscle group activation set encompassing much of the lower body and the core stabilizer muscle groups - though with an exemplary activation of the quadriceps femoris due to the angle of resistance and the biomechanics of knee extension.

hack squat machine

With a closed kinetic chain and a moderate to high level of perceived exercise intensity, the hack squat is usually rated at a novice level of exercise complexity due to the many safety mechanisms built into the hack squat machine and the fact that the risk of injury is relatively low when compared to other lower body compound exercises.

Does the Term Hack Squat Refer to the Hack Squat Machine or Barbell Hack Squat?

Unless otherwise specified, the term hack squat will usually refer to the hack squat machine and its subsequent related exercise, though certain articles of fitness will indeed refer to the barbell hack squat as simply “the hack squat”.

barbell hack squat movement

For the purposes of this article in particular however, the term hack squat is meant to mean the primary exercise performed with a hack squat machine.

Can the Hack Squat be Combined with the Squat?

As both the squat and hack squat serve practically the same purpose and train much the same muscle groups, it is generally not necessary that one performs both the hack squat and the conventional squat within the same workout session - though that is not to say that it is not possible.

As the hack squat primarily utilizes the quadriceps femoris as the main source of force throughout each repetition, the posterior chain muscle groups such as the hamstrings and glutes are relegated to a secondary role, a factor otherwise not present in the traditional squat.

barbell full squat

This can equate to the squat and hack squat both having a place within the same workout session, so long as proper programming and avoidance of overtraining is adhered to.

What Muscles are Worked by the Hack Squat?

For the most part, the hack squat recruits every major muscle group in the lower body to a significant extent, with a particular focus on the quadriceps femoris - as was previously mentioned earlier in this article.

Muscle groups such as the gluteus muscle group and the hamstring muscles along the rear of the femur are also recruited to a significant capacity, though not in as distinct an intensity as the quadriceps, thereby placing them in the category of secondary mover muscles.

Though a major characteristic of machine based exercises in a reduction or total elimination in the activation of stabilizer muscle groups, the hack squat nonetheless does recruit the abdominal muscles and the erector spinae in such a capacity - as it is a movement that requires the exerciser to stand upright during the apex of the repetition.

Other muscle groups that may be activated in a small but nonetheless noticeable capacity are the hip flexors and the many muscles of the calves.

Why Should the Hack Squat be Used?

The hack squat is best utilized either as an adjunct to heavier free weight resistance training exercises such as the deadlift or Bulgarian split squat, or as the primary lower body compound exercise in the workout session provided that additional lower body isolation work is also utilized.

As such, quite the hack squat is capable of fulfilling quite a number of roles within a training program and as such can aid the exerciser in achieving a variety of different training goals - with higher repetitions allowing for greater muscular hypertrophy such as in bodybuilding split routines, or the quadriceps-focused training stimulus aiding in the development of lower body eccentric squat-related contraction.

How is the Hack Squat Performed?

Setting Up the Hack Squat

In order to begin performing the hack squat, the exerciser must first position themselves accordingly within the padded portion of the hack squat machine once an appropriate level of resistance has been set up.

Placing the legs slightly closer than shoulder width apart with the knees and feet pointed at an outwards angle atop the angled footrest, the exerciser should find the padded portions of the machine resting comfortably along their shoulders as they face outwards - that is to say, in the opposite direction of the machine. If available, they may also grip the handles above the padded portion for additional stability.

Performing the Hack Squat

Once appropriately set up, the exerciser will then bend at the hips and knees in a simultaneous fashion, bracing their core and maintaining a neutral spinal curve as their hips are drawn backwards - all the while squeezing their glutes or buttocks so as to maximize muscle group activation.

If performed correctly, the exerciser should find themselves descending until their hips are parallel or below parallel to their knees as their feet remain flat upon the angled footrest - ensuring that a full range of motion is achieved and that the quadriceps are activated to the greatest extent during the repetition.

Once the first phase of the exercise has been completed, the exerciser will then begin the second portion of the repetition.

This is done by the exerciser driving their feet into the footrest in a slow and controlled manner, retaining a braced core and neutral spinal curve as the quadriceps and glutes are squeezed, thereby extending the knees and hips and once more raising the exerciser into a standing position in opposition to the resistance of the hack squat machine.

This completes a single repetition of the hack squat exercise, with subsequent repetitions simply requiring that the exerciser repeat the motion until the set has been completed.

Benefits of the Hack Squat

As a highly effective resistance compound exercise, the hack squat is capable of imparting a myriad of beneficial effects to the exerciser that chooses to perform it repeatedly over the course of many training sessions - with some of these effects being characteristic of the hack squat itself and are otherwise difficult to achieve with the performance of other exercises.

Novice Friendly Compound Exercise

The relatively simplistic form cues, built-in safety mechanisms and reduced stabilizer muscle group recruitment of the hack squat exercise all equate to a movement that is not only easier to perform for advanced weightlifters but also one that is considerably quite suitable for novice exercisers as well.

The hack squat is more than capable of preparing a beginner weightlifter for the form cues and feeling of performing a barbell squat or similar movement, allowing it to not only recreate the training stimulus of said squat with less risk - but also aiding in the novice’s learning of important weight lifting mechanics needed later in their training career.

Higher Maximal Weight Load

Like many other machine based exercises, the hack squat’s reduced usage of stabilizer muscle groups equates to more force and energy being directed towards actually moving the source of resistance - directly allowing the exerciser to lift more weight per repetition than they would be capable of with the hack squat’s free weight counterparts.

This presents several additional benefits, such as the capacity to condition the central nervous system to greater muscle group activation in such a capacity and therefore aiding in total strength output in other exercises, as well as allowing the exerciser to become used to moving such levels of resistance, as may be useful in powerlifters and similar athletes.

Conventional Squat Carry-Over

The conventional barbell squat is considered to be among one of the best possible lower body exercises available, with a reigning place in the majority of modern bodybuilding and strength training workout routines.

As the hack squat shares many similar characteristics, muscle groups activated and levels of intensity to the barbell squat - performing it either as a preparatory exercise or off-season counterpart to the aforementioned barbell squat will greatly aid in its performance, both strength wise and in terms of execution.

Low Risk Conditioning Tool

Conditioning an athlete or exerciser’s entire body and psyche to intense exercise comes with its own set of risks - with such matters like elevated stress levels, greater metabolic expenditure and even risk of injury being presented with many conditioning routines or exercises.

However, this is not entirely the case with the hack squat; with its many safety mechanisms, low risk of injury and relative simplicity of execution allowing many strength and power athletes to condition their nervous system, mind and connective tissues to highly intense weightlifting without significant risk of the aforementioned factors.

How to Program the Hack Squat

Being an intense compound exercise, the hack squat usually takes the place as the first or second lower body movement during a workout session - with more intense and complex exercises such as the deadlift or squat taking precedence over the hack squat.

Even in instances wherein the hack squat is used as an auxiliary exercise, it is still performed before any lower body or core isolation exercises are done - as performing such exercises before the hack squat may lead to overtraining or a breakdown in form.

In terms of workout programs utilizing some form of periodization strategization, the hack squat shares equal capacities for strength-building blocks, endurance blocks or hypertrophy blocks due to its high versatility in terms of volume and level of resistance.

Common Mistakes of the Hack Squat

Though the hack squat is considered to be quite safe, two main mistakes made during its performance can nonetheless place the exerciser at risk of minor injury or reduce the total training stimulus received by the exercise - requiring that they be remedied immediately.

Internally Rotated Knees and Feet

Just like in any other resistance exercise that involves the lower body, internally rotating the knees and feet can lead to significant pressure being placed on the patellar joint and its surrounding connective tissue - as well as reduce the total training stimulus placed on the hamstring and quadriceps muscle groups.

hack squat bad form

Fortunately, remedying this mistake simply requires the exerciser to ensure that their knees and feet are always pointed at a slight outward angle, and that the glutes are squeezed throughout the repetition accordingly.

Bouncing at Bottom of Repetition

Less an issue of form and more of form execution, the exerciser descending excessively quickly during the initial phase of the repetition and then rising just as quickly reduces many important components of the hack squat’s training stimulus, especially in regards to isometric muscle recruitment that is best achieved by slow and controlled repetitions.

In addition to this, bouncing also places the exerciser at significant risk of injury due to additional strain being placed on the knees and ankles as the exerciser’s bodyweight crushes the tissues therein - apart from the fact that it is likely the exerciser will break away from proper form with such an uncontrolled and explosive movement.

A proper repetition of the hack squat should be performed in a slow and controlled manner, with a moment’s pause being made at the bottom of the repetition as the exerciser squeezes their musculature so as to maximize training stimulus accrued.

Conclusion

In conclusion; the hack squat is doubtless an excellent exercise that can otherwise be overshadowed by certain other lower body compound exercises that do its job better - making it more appropriate in the training of novices, exercisers with a history of injury or as a secondary compound movement alongside other lower body exercises.

References

1. Schwarz NA, Harper SP, Waldhelm A, McKinley-Barnard SK, Holden SL, Kovaleski JE. A Comparison of Machine versus Free-Weight Squats for the Enhancement of Lower-Body Power, Speed, and Change-of-Direction Ability during an Initial Training Phase of Recreationally-Active Women. Sports (Basel). 2019 Sep 30;7(10):215. doi: 10.3390/sports7100215. PMID: 31574918; PMCID: PMC6835729.

2. Sigmon, Chip C.S.C.S.1; Duncan, Daniel E. C.S.C.S.2 STRENGTH TRAINING MODALITIES, National Strength and Conditioning Association Journal: August 1990 - Volume 12 - Issue 4 - p 28-32

3. Martín-Fuentes, I., Oliva-Lozano, J. M. and Muyor, J. M. (2022) ‘Influence of Feet Position and Execution Velocity on Muscle Activation and Kinematic Parameters During the Inclined Leg Press Exercise’, Sports Health, 14(3), pp. 317–327. doi: 10.1177/19417381211016357.

Debbie (Deb) started powerlifting and Olympic lifting in High School as part of her track team's programming; She continues to train in order to remain athletic. Inspire US allows Deb to share information related to training, lifting, biomechanics, and more.
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