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Are Leg Extensions or Leg Curls Better?

Last updated: June 8, 2022

If you feel confused when you are at the gym, don't worry, even the most seasoned of athletes aren't sure of which workout (or most commonly, machine) they should be using at any given time. Your legs contain the largest muscle groups in your body, so it is extremely important to select the right exercise, primarily for utilizing the strength in your legs wisely to not build up too much lactic acid and put you out of commission for the rest of the workout. Leg extensions and leg curls are the most popular leg isolation exercises in and outside the gym.

In this guide, we'll take a deep dive into both leg extension and leg curl, and look at both the benefits and focus of each routine. Finally, we'll list which one is the best exercise for your particular situation.

Unless you have suffered an injury in one of the muscles (quads vs hamstrings), both should be done on the same leg day, as both offer benefits and a range of motion for other daily activities and harder lifts. For example, squats are the most commonly performed compound lift in the gym. You perform a leg curl when you squat down, and a leg extension when you return to your standing position. By performing both leg curls and extensions, you can squat much more.

Leg Extension Vs Leg Curl

Leg curls and extensions can often be done apart, or put together into a superset, much like you would pair bicep curls with triceps dips/extensions. Both exercises are not compound lifts and aim to isolate a particular muscle group within the leg, hyper-focusing the training of the area for rapid muscle memory training, definition, and development. Let's take a look at each workout in detail:

Leg Extension

Leg extensions can be thought of as working the "triceps" of the leg, as it opposes the curl motion. Leg extensions are most commonly performed via machine assistance, as it is difficult to balance free weights on the front part of your leg. If you are at home, you can substitute resistance bands instead. The leg extension machine is padded with a grooved area allotted for the placement of your feet.

How to perform:  Start by sitting in the leg extension machine, with your back straight and relaxed. Place both your feet into the grooves in the padded leg holders. Adjust the weight with your hands so that it is comfortable for your workout, less weight for conditioning, and more weight for strength training and focus. Raise your legs slowly and simultaneously to properly propel the weight upwards. If the weight feels slightly heavy, push down the handlebars with your arms to give you that extra push to finish your set.

What muscles does it work?: Leg extensions work many of the auxiliary muscles in the front of your leg, as well as your front knee joint, and help to build strength along the shins and ligaments. Of chief importance is the quadriceps, which is the primary muscle worked in this movement. The quadriceps are the largest muscle group in the leg and help with many leg extension movements, kicking harder, running faster, more revolutions when cycling, and even better compound lift strength, such as squats and deadlifts.

Leg Curls

If leg extensions are akin to the "tricep dips/extension" of the leg, then leg curls work just like arm curls, which primarily focus on the biceps. It is so aptly named as the same "curling" motion that occurs during a workout and is usually done with the assistance of a machine as it would be even more difficult to balance a free weight during this movement compared with leg extensions. Because our knee joint only lets us curl backward, it is difficult to perform without a machine. If you are using resistance bands, it's recommended to have a spotter

How to perform: Leg curls are done in the "leg curl machine" (fancy right?) which is similar to the leg extension machine, except it features the opposite motion. You will need to set up the weight beforehand, as you will be lying flat on your stomach for the duration of the set(s). Once set up, lie down flat on your stomach with your body relaxed and straight. Place your legs in the curl pads and try to move them around to gauge a secure grip. Your foot shouldn't have any room to jiggle out of the holding. Grip the handles with your hands and engage your core, and perform the curl motion - as much as you can - up to a perpendicular angle. If you cannot reach 90 degrees, it's better to remove some weight, as great form often beats heavyweight with improper form.

What muscles does it work?: Leg curls work many of your joints and ligaments as well, but it primarily targets the hamstrings. These muscles are important for physical exercise, carrying heavy loads, and helping with compound lifts. Leg curls also engage the midsection and knees much more, strengthening the stabilizer tendons in your knees and increasing the balance that comes with a strong core.

Final Decision: Which One Is Better?

The best answer is: that they are of equal importance. Unless you have suffered an injury in one of the muscles (quads vs hamstrings), both should be done on the same leg day, as both offer benefits and a range of motion for other daily activities and harder lifts. For example, squats are the most commonly performed compound lift in the gym. You perform a leg curl when you squat down, and a leg extension when you return to your standing position. By performing both leg curls and extensions, you can squat much more.

FAQs

Can leg curls replace deadlifts?

Deadlifts are a unique compound movement that aims to focus on the muscles that are not isolated during the squat and are often combined into a strongman strength training workout. It targets the shoulders, back, hip, leg, and stabilizer muscles. Leg curls cannot replace the importance of deadlifts but can be one of the exercises done to prepare for them. 

Can I do leg extensions after hip replacement?

Post hip replacement, it is important to follow your aftercare routine. Leg extensions can be done after a few days of healing if they are done as a motion and without any weight. It is important to consult your healthcare practitioner when you are cleared to start with weight-assisted machine exercises such as leg extensions.

How do quadriceps and hamstrings work together?

They work much like an arm would work. When you bend or curl your leg, your hamstrings contract, taking pressure off the quads. The quads are activated when you straighten your legs and let your hamstrings relax. This is the basic movement of running or walking.


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