Knee Extensions are Good Exercises

November 07, 2012

Powerfully effective for strengthening the quadriceps musculature

I was contacted yesterday by someone who asked me the following question:

Dear Mr. Hahn,

I just wanted to say that I heard you on Jimmy Moore's podcast, bought your book, and I've been doing slow burn for a couple of weeks now and have already started seeing results. I am 44 and concerned about getting injured, so I think your method is perfect for me.

I have a question regarding my wife. She is in good shape by appearances, but admits that her muscles are weak and could use some strength training. But she has a concern with doing the leg press or knee extensions. She has some joint issues (particularly in the knees), and a physical therapist once told her that no one should ever do a knee extension, as it is really bad for that joint. She is also concerned about squats and presses. Do you have any advice about how she can strengthen her legs without hurting her knees?

Thanks so much for your help!

I just hate these physical therapists. Well, hate's the wrong word - despise is closer to it.

Let's get down to it here - no matter what strengthening exercise you do HOW you do it matters. I think we can all agree that fast and explosive movements on ANY exercise machine or free weight exercise using challenging weight loads is a recipe for disaster. If you don't agree with this, hit your back button and follow the election results.

Instead of flinging your limbs around like a rag doll when lifting weights, slow and controlled movements impart a much lower degree of force without compromising gains in muscle tissue - the ultimate goal of weight lifting for health and fitness.

Here's a video showing some guy doing them wrong:


Here's me doing a very heavy set of knee extensions (heavy for ME that is) a couple of years ago. Bear in mind that I have severe knee arthritis due to 25 years of Karate, jogging, etc. and perrform this exercise with ZERO knee discomfort.

Also bear in mind that I always train myself, so, you'll see some questionable exercise form. Bear further in mind that I was a little tubby then from rice and sweet potatoes creeping into my life. I was trying to carb up a bit to increase muscle fullness and it resulted instead in a fat gut. Lesson learned.


For people with knee issues, I'd advise a rep range of 6-12 repetitions. This keeps the weight a bit lighter.

Now, some therapists and personal trainers will argue that the exercise isn't "functional." They claim that we don't use our legs in this fashion in real life, meaning, we don't extend our knees against resistance while sitting on a chair. My answer: So what? The issue is the strength of the quadriceps and nothing more. Do these therapists think that if I make Mrs. Smiths quads 50% stronger by making her quads more muscular they will look nice but won't function any better?

They also claim that it puts undue pressure on the kneecap forcing it to crush up against the femur causing compression and potentially injury. But of course, these same therapists go out for their morning jog. The reason for knee injury when doing leg extensions is not due to the exercise itself. It is due to HOW you perform it.

You can't jog carefully and slowly. If you put a chimp behind the wheel of a car and it crashes, don't blame the car.

As the saying goes, slow and steady wins the race. Your thoughts?