The Leg Extension Machine

The Leg Extension Machine

What is a leg extension machine?

The leg extension machine is designed to target the quadriceps (the big muscle located at the front of your thigh) in the leg. The basic principle is you sit on the machine with your legs bent 90 degrees at the knee while your lower part of your legs are behind a padded bar. You then extend your legs up to the straight position while moving the padded bar up. Once at full extension, you lower the bar under control to the lower position. This movement specifically targets the quadriceps (quads) in the legs and is known as an isolated exercise.

leg extension machine


Cable leg extension machine construction

The mechanics behind how this machine works is with the cables, and the utilization of the principle of levers. If you look at the construction of a cable leg extension machine you will see a cable attached to the weight stack. This cable is routed over a number of pulleys in order to orient at the other end of the cable so it is attached to the section you raise with your legs. Some machines have this attached directly to the bar, whereas others have a cam or large disk the cable runs in. Either way, the mechanical result is the same: when you extend your legs, you raise the bar which pulls the cable, which in turn lifts the weight stack.


cable leg extension


The seat back is generally adjustable so that you can move in, back or forward, to position your inner knee joint at the edge of the seat. Most machines will have hand grips on each side of the seat, and this is good because it allows you to grip and maintain a good posture throughout your leg movement. If you do not use the grips, there is a chance that you will lift yourself off the seat during the exercise due to the weight at the other end of the cable system.


The padded bar you place your legs behind should also be adjustable, which allows you to position the bar at your ankles; this lets you give the maximum effort in this workout motion while maintaining comfort.


leg workout with leg extension


The only other adjustable feature would be the weight stack where you can select the appropriate weight by placing a pin in the desired weight position. Most machines have a weight stack starting at 10 lb with 10 lb plate increments. A home or light commercial leg extension machine may have a weight stack of 160 lb whereas a heavy commercial machine could have a weight stack of 260 lb or more.


The benefits of leg extension exercises

As the leg extension machine targets the quads, adding this exercise to your workout will help increase the size and strength of your quads. If you are looking to obtain the bodybuilder physique, then muscle isolation workouts will be your core style of workout. The leg extension machine should be part of your equipment, as this gives a very specific isolated workout for the development of your quads.


The cable leg extension machine is also used effectively for rehabilitation exercises for those people who have had knee or other leg surgery. The isolated workout on the quads and the movement in the knee helps with the initial rehabilitation phase.


Light commercial or heavy duty commercial?

If you are looking to add the cable leg extension machine to your gym equipment, we think you need to consider the ‘level’ of machine you are going to purchase.


Light commercial

The light commercial level machine would be very suitable for any home or garage gym as these are designed for light use, dozens of times a day, which in the home gym routine would be way excessive. These machines are aimed at the hotel gym or the shared condominium style gym where the throughput of gym users is not that many.

 light commercial leg extension machine

The light commercial machines are very well constructed with full adjustment and high grade materials being used in their construction. The weight stack would generally provide a total weight of around 160 lb, maybe more with some brands. This is generally enough for the gyms they are targeted towards, including most high end home gyms.


Heavy duty commercial

The heavy weight commercial level machines on the other hand are designed for hundreds of uses per day and can be found in most membership style gyms. The construction of these commercial level machines will use heavier grade materials such as steel, cables and a heavier duty fabric and even the stitching on any padding.

heavy commercial leg extension machine

The cost of these commercial leg extension machines will be higher than the light commercial because of the materials used and they would have a heavier weight stack, often over 250 lbs.



If you are looking to increase the size and strength of your quadriceps then the isolation exercises you can do on a leg extension machine makes it a clear “go-to” piece of equipment for anyone intent on developing their leg muscles. By sitting on the machine and extending your legs while raising the padded bar, you are lifting the weight stack.


There are different levels of this type of machine; the light commercial machine is aimed at home gyms, hotel and condominium style gyms where the daily use is light, and the heavy duty commercial machine which is designed for hundreds of users per day and is aimed at the membership style gyms.


There are multiple brands available on the market, however, we at Gym Gear Direct are focused on providing both light commercial and heavy commercial cable machines from TKO Strength.