The hack squat and leg press are a pair of lower body compound exercises usually involving assistive machines that allow the exerciser to move large amounts of weight in a safe and controlled manner, reducing the chance of injury and allowing a more significant load be placed on the muscular tissue.
Owing to their machine assisted nature, both the hack squat and leg press provide less training stimuli to the various stabilizing muscles normally involved in leg focused compound exercises. This may be beneficial in the event that the exerciser has suffered some sort of injury or otherwise would prefer to only activate the primary muscle groups involved in these exercises.
Generally, both the hack squat and leg press are equally viable exercises that may be incorporated as a lower leg compound movement into a workout program or rehabilitation plan. However, minute differences between the kinetic action behind each individual exercise may provide differing training stimuli and muscular activation, of which must be accounted for.
The hack squat, being a mostly upright leg exercise, generally focuses on the quadriceps femoris muscle owing to the fact that the four heads of the quadriceps femoris are primarily responsible for the extension of the knee joint, of which is used during the concentric portion of the exercise.
While the quadriceps femoris is the primary muscle activated while performing the hack squat, this exercise is still considered a compound movement and as such also incorporates many other muscle groups located in the lower body, such as the gluteus maximus, the abdominal muscles, the hamstrings, the erector spinae and the many smaller muscles grouped together under the hip adductors.
A bilateral push movement, the hack squat will activate these muscles in an even manner across either side of the body, so long as the proper form is being utilized and the feet are placed exactly the same width apart.
The leg press, unlike the hack squat, generally involves the exerciser either lying flat on their back or seated with their legs upright in an incline position.
This small change in position alters the dynamics of the exercise, placing a different emphasis on other muscle groups that only act as secondary activators when performing the hack squat.
Primarily, the leg press also activates the quadriceps femoris, as both hack squat and leg press involve significant force being released through the extending of the knees, of which the quadriceps femoris is directly responsible for.
However, the leg press differs from the hack squat in the fact that it recruits a significantly higher percentage of muscle fasciculi in the soleus muscles of the calves as well as the many smaller muscles in the hip adductors.
Unlike the hack squat, the hamstrings only act as minor stabilizer muscles while the leg press is being performed, making the leg press a far more quadriceps centric exercise.
Also a bilateral push movement, the leg press activates both sides of the lower body equally, though this requires the utilization of proper form.
Unfortunately, the drawback to utilizing machine assisted exercises is that the mechanical nature of their mechanisms eliminates much of the need to stabilize the weights through the exerciser’s own musculature.
This means that, unlike machine exercises such as the leg press and hack squat, free weight exercises require the lifter themselves to keep the weight steady.
Because of this, depending on the particular exercise and biomechanics of the exerciser, certain muscles that are activated in the free weight equivalent of the machine assisted exercise will otherwise not be stressed or trained.
For example, an excellent alternative to the machine assisted leg press is the commonly practiced barbell squat.
Unlike the leg press, the barbell squat rests a considerable amount of weight atop the torso as the exerciser holds themselves in an upright position. In order to ensure that the weight is comfortably supported, the abdominal muscles and obliques work to balance both the torso and the bar atop it. This does not occur as much during the leg press, because the leg press machine itself is holding the weight stable.
However, this is not always a drawback, as less energy being spent on the stabilizer muscles may allow the exerciser to exert more force through the muscles that are otherwise being activated by the machine assisted exercise.
Apart from the regular general health benefits to performing resistance exercises, the hack squat also provides numerous other positive aspects to the exerciser.
If performed properly, the hack squat can induce significant hypertrophic growth to the quadriceps femoris, hamstrings, abdominals, gluteus maximus, and the hip adductor muscle group.
The vast majority of the lower body’s muscle groups are activated and involved when performing a hack squat, helping to prevent muscle imbalances and reduce the chance of injuries.
Because the hack squat is a machine assisted exercise with built in safety measures, it is quite difficult to injure oneself while using it so long as the exerciser is utilizing a comfortable amount of resistance as well as performing the exercise using proper form.
The hack squat is also an excellent way to acclimate new weightlifters to the sensation of performing a squat under significant resistance, though the particular form utilized while performing the machine hack squat is not quite the same as a free weight barbell squat.
Much like the hack squat, the leg press provides many benefits to the exerciser, so long as it is performed with the proper form and an appropriate level of resistance.
Being a strength-based exercise, the leg press is capable of causing muscular hypertrophy in the quadriceps femoris, parts of the calves and the hip adductors.
Depending on the width of the exerciser’s stance, the exact level to which these muscles undergo mechanical tension may vary, with certain muscle groups bearing more of the weight than others.
For instance, placing the feet wider and higher on the leg press platform will increase gluteal muscle activation.
Apart from hypertrophic induction, the leg press is also an excellent way to train the leg muscles of an individual who is not capable or not a suitable candidate for performing other free weight leg exercises, such as members of the elderly population as well as individuals with certain types of injuries.
As always, first consult with a physician before attempting this exercise.
The hack squat is quite a safe exercise for most healthy individuals, especially considering the fact that the hack squat machines are usually built in such a way that safety mechanisms will activate in the event that something goes wrong.
However, even with built in safety features, individuals with lower back issues as well as those who suffer from chronic injuries involving the patella and surrounding joint structure may still manage to injure themselves while performing the hack squat.
Instead, it is best to use exercises that bring the legs to a different angle or utilize much less resistance, unless otherwise directed by a coach or medical professional.
Apart from individuals with certain types of injuries or disorders, those seeking to train to their maximum possible effectiveness such as athletes undergoing power training or strongman athletes training for a meet should most likely replace the hack squat machine with a barbell hack squat instead.
This is due to the previously mentioned fact that the hack squat machine tends to stabilize the weight by itself, causing the accessory muscles normally involved in free weight leg exercises to be left untrained. This may translate to minor muscle imbalances or an otherwise incomplete level of training.
The leg press is much the same as the hack squat in the fact that it is quite safe to perform so long as a reasonable level of resistance is used and the individual performing the leg press is healthy and uninjured.
And just like the hack squat, the leg press is also often built with safety mechanisms involved, preventing the weight from injuring the exerciser in the event that anything untoward may occur.
If the individual performing the leg press has recurring injuries or impingements around the lower body, though, it is best to switch out the leg press in their exercise routine for something that places less stress on the connective tissue at that particular angle, such as bodyweight squats or other individual machine assisted leg isolation exercises.
The machine hack squat is quite easy to perform and only requires a small amount of weight be placed on the machine.
To begin, first load the machine with a moderate amount of weight. Lay the exerciser against the padding of the seat if the machine is at an incline, or otherwise stand beneath the shoulder pads, with the exerciser holding a small amount of tension in their body as if preparing to jump. The machine should be adjusted so that at rest, the exerciser’s legs are slightly bent somewhat and not fully extended.
The exerciser will place their feet facing slightly outwards, planted approximately shoulder width apart. Depending on the machine, the safety lock or handles may first need to be disengaged before beginning the first portion of the exercise.
The exerciser will then lower themselves by bending their knees until they are parallel with their hips at the least. All the while, the exerciser must brace their core and keep their spine as straight as possible, facing the head forward and maintaining a stable torso by pressing against the shoulder padding.
The concentric portion of the exercise now complete, the exerciser simply needs to raise themselves back to their starting position by exerting force downwards through their legs, straightening at the knees and hips.
Keep in mind that it is best not to fully lock out the knee (as pictured above) as this may result in impingement or patellar dislocation.
Being a machine assisted exercise suitable for beginners, the leg press is not difficult to perform in any way, and only requires weight plates in order to add resistance.
To prepare the machine for use, load it with a low amount of weight, especially if the exerciser has not performed a leg press before. Ensure that the machine is evenly balanced with weight plates of the same denomination on both sides.
The exerciser will then either lay horizontally on the seat if the machine is of the horizontal type or otherwise lay at an angle against the padding if the leg press machine is of the forty five degree angle.
Bracing their legs against the metal plate by placing their feet shoulder-width apart with the toes facing slightly out, the exerciser will then disengage the safety lock handles usually placed near their padding or seat.
Ensure that the exerciser never locks out their knees, as this may cause dislocation.
Bracing their core and retracting their scapula, the exerciser will drive the heels of their feet into the metal plate, raising it and pushing it away from the exerciser. As they do so, the exerciser should ensure that their feet are kept absolutely flat against the plate.
Once the knees are nearly fully extended, they must then allow the metal plate to slowly fall back towards them, bending at the knees and hips in order to engage the quadriceps and calves fully. The repetition is considered complete once the knees are bent as far as is comfortable for the exerciser.
The leg press may be stopped by raising the plate back to its original position and engaging the safety lock handles once more.
1. Unknown Author. (N.D.) “Machine Hack Squat Video Exercise Guide” muscleandstrength.com Exercises category
2. Tony Caterisano, Mike Gentry (2005). A Chance to Win: A Complete Guide to Physical Training for Football. Champaign: Sports Publishing L.L.C