Stop Gossiping About the Innocent Leg Extension

Every gym I’ve worked at, there was always that one overly functional trainer or group of trainers who demonized the leg extension. According to these dorks, the leg extension is non-functional because nobody moves that way in real life and apparently the torque from the machine will grind your knee joint into a million pieces.

When I hear crap like this, it makes me want to slap these dorks off a bridge. Like a really high bridge that’ll cripple them out of the industry so they can’t regurgitate bad advice anymore.

I’m obviously kidding, well partially, but the point I’m getting at is the leg extension has always been innocent. The leg extension is like that kid in High School who sits in the corner avoiding drama, yet all these clueless losers talk smack about him.

If you’ve heard nasty things about this machine, here’s why you should reconsider.

Are Leg Extensions Bad For Your Knees?

Some trainers propose leg extensions are bad for the knee joint or surrounding connective tissues.

However, even at the most stressful angle (0-30 degrees), leg extensions apply far less stress than what’s necessary to damage tissue (1). In fact, leg extensions apply only a fraction of the force required to be a problem (2,4). Walking and jumping actually apply similar force levels (3).

Leg extension haters will say squat are safer yet squats apply ten times as much force on the PCL, a key ligament within the knee that aids in ACL strength (5-8).

Direct ACL strain is also similar between squats and leg extensions and may even be higher with squats (9). To be clear, I’m not saying squats are bad for your knees, but prescribing squats and saying leg extensions are dangerous is hypocritical.

Leg Extensions For Rehab?

So not only are leg extensions not bad for you, they could very well be what you need to manage knee pain (10). Leg extensions are the only movement pattern that can shorten all the heads of the quads including the rectus femoris (front of thigh) which can’t be fully shortened from squats.

The front of your quads simply don’t activate and grow as well without leg extensions (11,12). The idea that the pattern of knee extension being a non-functional pattern so it doesn’t need to be trained is idiotic. Your body possesses that pattern and recruits muscles differently from it so to cover your bases, leg extensions should be included (13,30).

Including leg extensions early on in a rehab setting is fine as well (14). Your knee won’t explode like the haters say.

In fact, research is very clear that squats plus leg extensions are better than squats alone for both PCL and ACL reconstruction along with strength and function (15,16).

Higher quad hypertrophy and all forms of quad strength are extremely strong predictors of the following (17-26):

  • Better Function
  • More Mobility (elderly populations)
  • Better Performance
  • Safer Landing mechanics
  • Reduced knee pain
  • Reduced cartilage damage
  • Faster Injury recovery
  • Reduced joint stress

For example, one study took athletes suffering from jumper’s knee (patellar tendinopathy) and had them do 12 sets of 8 leg extensions every week for a month (27). Their knee pain significantly decreased and their strength/function improved.

My Personal Recommendations

I personally have terrible knees from years of Wrestling and Jiu-jitsu. I can tell you leg extensions have been majorly helpful in managing my knee pain and knee function. I used to be skeptical of this machine in my first year as a trainer, but the rumors simply aren’t true.

Over the years, I’ve had numerous people from old ladies to athletic knee rehabbers use leg extensions consistently. They feel great doing them and we usually do them for higher reps (12+).

We still apply progressive overload just like you should with any other exercise by increasing weight and reps when appropriate.

It also goes without saying, this is only possible if your form is strict and you’re controlling the weight on the way down instead of mindlessly swinging your legs like a spastic monkey. Most people who experience knee pain on leg extensions are either using too much weight or lifting with garbage technique.

As for setup, I suggest setting the seat relatively far back to get a deeper stretch in the quads and to grip the handles firmly for stability (28). You should set the pad at about ankle level, but you can move it higher if you’re worried about additional knee stress (29). Lastly, if your leg extension has a seatbelt, use it.

You can also get creative with doing leg extensions in different ways.

Here are my 3 favorite leg extension variations are:

  • Standard Leg Extensions
  • Alternating leg Extensions – Do one leg at a time
  • Leg Extensions with a Hip Hinge – I wrote a full article on this exercise years ago which I’ve never seen before so I’m claiming to be the originator of it cause why not right?

But long story short, anybody looking to rehab their knees, strengthen their quads, or grow thunder like thighs, you better include some leg extensions. Oh and be sure to send this article to any dummy that tries to say otherwise.

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30.

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