Why leg extensions are a better quad exercise than squats

Categories: Videos & podcasts


00:00 Introduction

00:32 The problem with squats

01:29 Studies

02:33 Optimal way to train the quads


Squats are famous mass builders, widely regarded as one of the top exercises for the quads, their reputation is largely justified. Leg extensions don’t quite have the same reputation. However, the idea that just squatting is best for your quads and that leg extensions are a poor secondary exercise for the quads is false. In fact, it is technically the other way around. Leg extensions are the more complete quad exercise compared to squats. See, the problem with squats is that they don’t train the rectus femoris. As I explained in my other video so rectus femoris is the muscle of the quads in the middle of the quads here. And, when you want to activate this muscle, you have to take into account that it’s bi-articular.

So it crosses the hip and the knee. And as a result of that, it shortens when you lift up the leg because it’s now contracting at the hip. Therefore, during a squat when the knee is up and your hips are flexed in the bottom position of a squat, the rectus femoris cannot actively participate without disrupting hip extension forces. If the rectus femoris in the bottom position of a squat contracts, yes it’s trying to extend the knee, which would be good, but it’s also dragging you down in further hip flexion, whereas you want to come up and extend the hip. As a result, we see in research that muscle activity of the rectus femoris during squats is very low – and it makes perfect biomechanical sense. We also see in research directly comparing leg extensions to both leg presses and squats. We see that leg presses and squats are relatively ineffective, in fact completely ineffective in many studies to grow the rectus femoris. Whereas leg extensions produce growth in all heads of the quads roughly equally well. Thus, we can say that leg extensions as a simple knee extension exercise, they activate and grow all of the knee extensors very well, whereas squats basically only train the vasti – vastus medialis and the vastus lateralis.

Other lower body, squat or deadlift type movements don’t perform considerably better. A study by Fonseca et al. compared the same volume of either just barbell back squats or a combination of squats, leg presses, deadlifts and lunges for rectus femoris. The combination group trended to achieve more robust growth of rectus femoris but the growth rate was still below that of the vastus lateralis and the vastus medialis. So any squatting type movement is going to be sub optimal for the rectus femoris. And it is particularly annoying if you train in a home gym or any type of gym that doesn’t have a leg extension machine because you need ideally leg extensions. Or alternatively, another exercise that trains the rectus femoris or hip flexors very well to get complete quad development. The rectus femoris is not the most important head of the quads, It doesn’t give you the sweep, it doesn’t give you a teardrop at the knee, but it does provide a nice, meaty extra part in the middle, especially for physique competitors to get lean enough to show the striations and the muscle separation there.

So squats are great, leg extensions are great and they complement each other very well. They also complement each other well because leg extensions, typically depending on the machine used, emphasize the shortened position they are hardest when you extend the knee the most, whereas with squats you can go very deep. Unfortunately, most leg extension machines don’t allow for full range of motion, which is a tragedy because research finds that the deeper you go, the more you lengthen the quads the more they grow, which is called stretch mediated hypertrophy. Now you can either combine squats and leg extensions in the same program. That typically works super well. One is open chain, one is closed chain. So the different kinetic chains also complement each other well in terms of different joint stresses, different stimulus, perhaps slightly different regional hypertrophy due to these differences in muscle activation. Or what you can do is you can do a squat type movements and add a hip flexor movement. You can do hanging knee or leg raises, for example, but they don’t train rectus femoris as well at long muscle lengths. My personal favorite exercise, if you go this route, is to perform lying hip flexions. So lying leg raises and here you have to differentiate them from a reverse crunch.

Where you actively involve a crunch type movement to train the ABS. If you purely use the hip flexors, so you just have to legs that go up like a bridge. You’re pulling them up like a bridge. It’s best to perform this on a bench so that you can get extra depth in the bottom. If you perform them on the floor, then your heels are going to touch the floor in the bottom position. They cannot go more than horizontal on a bench. They can go a little bit lower, get that nice stretch on the hip flexors and then like a drawbridge you pull up the legs without actively performing a crunch type movement, unless you also want to train the lower abs or your abs in general. If you’re wondering, aren’t leg extensions unsafe, then you should subscribe to this channel because I’m going to talk about that in my next short video.

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About the author

Menno Henselmans

Formerly a business consultant, I've traded my company car to follow my passion in strength training. I'm now an online physique coach, scientist and international public speaker with the mission to help serious trainees master their physique.

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