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Barbell Leg extension as main quad mover

Michael Brian Turner

Level 3 Valued Member
I'm confused about the hate the leg extension gets, understandably, doing them stupidly heavy would lead to stupid results, however, high repetitions and concentrating on contraction is a Saint.

The thing is, the older I get the worse my knees are due to past mistakes that are resulting in arthritis even at 31 years old however with that being said I train at home and normally do squats but it's now apparent that these are bothering me now which even light weights are too.

I've had my form checked and everything is fine, it's just appearing the arthritis doesn't like it lol, but what doesn't hurt is leg extensions/leg Curls.

So why all the hate for leg extension when done properly target all the musculature in the quad? I understand that the squat is the king and I'd be the first to agree to this too.

So who else exclusively doesn't squat or instead does extensions?

william bad butt

Level 6 Valued Member
Are you doing low bar "powerlifting" squats (hip dominant) or high bar (knee doninant) squats. If you have knee issues, try the former.

And if you cant do any squatting, can you do good mornings with partial knee flexion, without pain?

I occasionally fo leg curls and leg extensions. I'm not too serious about then though. Honestly, I've come off those machines with my knees feeling a bit uncomfortable (pain would be too strong of a word).



Mark Limbaga

Level 7 Valued Member
Elite Certified Instructor
You can go ahead and do some leg extensions if you feel they work for you.

I would recommend however getting your form checked and being able to keep a squat pattern (think sitting in the toilet) has multiple uses

Steve Freides

Senior Certified Instructor
Elite Certified Instructor
@Michael Brian Turner, I'd like to question some of the assumptions you're making in your post. I'll start by saying you're right, leg curls and leg extensions can be great muscle builders for your legs. And you're right again that, if you can't squat, those exercises might be the best choice for you.

But around here, we like to talk about movement more than about muscles. I'd like to suggest that you've perhaps given up too soon on squatting, and that if we can help you fix the movement pattern that is the squat, perhaps you can still perform it and, overall, it will always be a better choice as a primary exercise for your legs than extensions and curls will be because all large, compound movements are a better choice, overall, for anyone without a specific reason to avoid them.

I'd like to see a video of you performing a goblet squat with a kettlebell or dumbbell. Let's see if we can help you squat again. Unweighted, or lightly counter-balanced squats like the goblet squat are things we hope everyone can do. I'm still doing them at more than twice your age and with knees that, after 25 years of bad running form, aren't in very good shape, e.g., I can't do anything "tall kneeling" because I can't put weight on my cartilage-less knee caps, but I can still squat.



Level 6 Valued Member
I'm not sure if this thread is a response to my comment in your other thread (the minimalism challenge one), where I implied leg extensions are not a great choice if one is pursuing minimalism.

All the same, if hypertrophy is your goal, leg extensions can be good for getting volume in, but that strategy only really works if you're using something else to get properly stronger (a Squat variation or leg press).

Leg extension alone won't give you strong or big legs. Added as a spice to the main dish of compound exercises, they can help you build bigger legs than the aforementioned compound exercises alone.

Kenny Croxdale

Level 6 Valued Member
I'm confused about the hate the leg extension gets,

Leg Extensions

Overall, Leg Extension don't have much value of the majority of individual. The are not what is considered to be a Functional Exercise for daily activities.

Secondly, Leg Extensions place a lot of Shear Force on the knees. Few Physical Therapist advocated them.

Leg Extension in which your legs are fold back underneath you too far, place an incredible amount of torque on the knees, Shear Force.

Individual who preform Leg Extension need to limit the range of the movement.

This bring us to one movement that many Physical Therapist recommend...

Quad Sets for Quadriceps Activation

This article provide some good information.

Regaining Knee Extension After Surgery! | Episode 21

This video from the article provide some great Quad Extension Strength Training Movements.

Biking For Quads

Exercise Bikes are synonymous with for individual with Knee Issues.

Essentially, an Exercise Bike is a one Legged Leg Press; it is a Quad Dominate Exercise.

A Bike provides Concentric Only Contractions. One of the benefits is Concentric Only Training allow for quicker recovery.

There is no Eccentric Loading; more recovery is required from exercise with that component.

doing them stupidly heavy would lead to stupid results,

"Stupid Is As Stupid Does"

As you know, the Leg Extension isn't an exercise, for anyone, that you can go heavy on.

Individual who can move a lot of weight on a Leg Extension are "Launching It" with momentum; which is idiotic.


Level 2 Valued Member
“A Bike provides Concentric Only Contractions. One of the benefits is Concentric Only Training allow for quicker recovery.”

Same with sled/prowler/car pushes.

Cut and paste…​

Enter the Sled!​

The advantage heavy sled pushes have over heavy squats lies in the contrast between their eccentric loading patterns. During a heavy sled push the legs are only forced to work against resistance during the concentric phase which occurs during the push against the floor. The eccentric portion of the lift happens when the leg is lifted and the knee bought forwards after finishing each step. This means that a heavy sled push will be quicker and easier to recover from than a squat with a comparably heavy weight, perfect for a Rugby player who will be back out on the pitch 48hrs after his gym session or a combat athlete in the last week or two of his fight camp when fresh (but strong!) legs are crucial.



Level 6 Valued Member
I had my first knee dislocation on a quad extension machine, after my first ACL tear the physios suggested that building quad strength was the best to way avoid surgery. So I got to the point where I was lifting the whole stack on the machine and adding plates & or dumbbells to it to make it heavier. So I had insane quad strength (I was also balancing it with hamstring curls on the same machine) but it didn't develop any lateral stability like a deadlift or squat does and one time my knee popped out sideways and tore my medial collateral ligament.
So I'm not a big fan of those machines, sure they have their place but I wouldn't put all my focus on it. They place an unnatural shear stress on the knee joint that it's not really "designed" for. I've managed a few gyms in my time and I've seen 4 other people get to the point where they were adding extra weight to the stack and they had the same dislocations as I did. For some reason the knee always seems to pop out to the front and then the lower limb twists and moves laterally in the cases I've seen (including my own).
Extensions are great for rehab in some situations and they're great for a pump (using high reps) if that's your thing but functional natural movements are always the best . If you want to use them for hypertrophy then that's cool but don't try to set any records in regards to the weight you're pushing, just go for reps with a reasonable weight.
Muscles (especially quads for a young man) develop really fast but the ligaments and tendons take a lot more time to catch up, so don't rush it if you chose to use quad extensions as your main quad exercise.


Level 6 Valued Member
Leg Extensions place a lot of Shear Force on the knees. Few Physical Therapist advocated them.

Leg Extension in which your legs are fold back underneath you too far, place an incredible amount of torque on the knees, Shear Force.
I’m curious: How is this shear force different than that experienced in a full butt to heels squat?

Philippe Geoffrion

Level 6 Valued Member
As @Steve Freides said, movements over muscles.

A leg extension does not have much transferable strength. As others have noted, it is not highly recommended as a therapeutic knee movement.

Squats, however are. Max Shank wrote an article on the benefits of rehabbing his knee after surgery with basic squats and returning to lift heavier barbell following a basic daily bodyweight squat rehab. As someone else mentioned, good mornings are valuable as well. The Bruce Randall story…

All that being said, if squats bother your knee, some posterior chain work might be needed. The hips, glutes and hamstrings are really the foundation of the lower body(good ankle dorsiflexion doesn’t hurt). SumoDL or even trap bar lifts will still hit the quads to some degree while taking stress off the knees.

Squatting to a box through your pain free ROM and learning to push the hips back might help. Knee problems and squatting can often be traced to the trainee push solely from the knees and trying to stay super upright. As someone mentioned…low bar squats.

We train movements over muscles because we like to harmonize the body to coordinate tasks in complete unison, like a well tuned orchestra. Cutting up your quads from leg extensions is like recruiting a guitar player who can play fast scales but can’t play through a convincing 12 bar blues.


Level 5 Valued Member
I’m curious: How is this shear force different than that experienced in a full butt to heels squat?

excellent question!

in a squat with a decent amount of load, you are getting a good deal of a compressive force downward through the knee joint, which offers more stability. This is why closed chain exercises are so safe and effective. Also, the direction of the lever arm in a squat does not allow for forward tibial shear.

With the leg extension, the lever arm is placed distal from the knee joint and the lever arm is shorter with no compression. So the proximal tibia is free to move in the direction opposite of the load force.

I need to be better like Kenny to offer you empirical data (plus I am horrible at explaining physics). In my line of work and own research, I have come across a a great deal of studies that look at shear forces of quad dominant exercises, with the leg extension being significant higher than other movements. It’s not even allowed in the greater majority of ACL rehab protocols I have come across.

In short, during the squat, the anterior force comes from your femur on a fixed tibia. In the leg extension, the anterior shear comes from the tibia on a fixed femur, placing greater stress on ACL and patellar tendon
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