Stop Crapping on Leg Extensions

Why They Have a Place in Your Training

Stop avoiding the leg extension machine if you want bigger, stronger legs. Bonus: It’ll make you better at the big lifts. Here’s why.

The leg extension machine has a bad reputation. It’s known as the machine lifters do when they just want to avoid harder compound lifts. But does that mean it’s useless? Of course not.

Here’s how to get the most out of the leg extension machine and the truth about what it will and won’t do for you.

Leg Extensions for Quad Growth

Leg extensions are a great way to place targeted tension through your quads. You don’t need a study to know it’s working. Exercises like these – that target the shortened range a little more – are notorious for their isolated squeeze and the burn that comes with it.

Some may argue that multi-joint exercises like squats and leg presses are enough to build strong quads. While squats activate three out of the four quadriceps muscles, they’re not as effective at activating the rectus femoris, the quad musculature that runs down the middle of the thigh. Supplementary exercises, like leg extensions, can address this shortcoming.

Leg extensions activate this area greater than squats (1). The timing of activation is also different (2). That makes the leg extension a good side dish to your meat-and-potatoes entree.

Rehabilitating Knee Pain with Leg Extensions

Always consider the risk-versus-reward ratio of any exercise. It’s person-specific. Leg extensions have both negative and positive impacts, depending on your circumstance. Numerous studies and real-world results show that leg extensions are beneficial in rehabilitating knee injuries, such as patellar tendinopathy.

Leg extensions provide a controlled environment where the load and range of motion can be carefully manipulated over time. For example, you could only extend your knee from 90 to 45 degrees (where load under the knee cap is lowest), then, as pain-free ranges of motion improve, explore ranges closer to full knee extension. You can also do them for eccentric strengthening protocols, which further benefits tendon health and loading capabilities.

Safety for Healthy Knees

Some argue that leg extensions are bad for the knees, but this isn’t true if you’re doing them correctly with an appropriate weight for your capabilities.

And they’re “bad for the knees” comparable to what? Leg extensions shouldn’t scare you if you’ve spent any time playing a field sport involving change of direction, unpredictability, and human collision. Heck, you’re more likely to injure yourself taking the dog for a walk!

Did you know the ACL can withstand roughly five times the force a leg extension machine can provide with virtually any weight and rep scheme?

The health of the ACL also depends on the strength of your hamstrings. If you’re not giving your hamstrings and glutes enough attention, then an increase in isolated quad strength may increase your risk of ACL injury. So, don’t be weak or have strength imbalances, and you’ll do a lot better than those arguing that leg extensions are bad for your knees.

For Strength Improvements

Consider exercise selection carefully to manage fatigue in your program. Leg extensions produce very little neurological fatigue, making them easier to recover from compared to big lower-body lifts. This is a good reason to sprinkle them in to complement, rather than detract, from your compound lifts.


Leg extensions are a good supplementary exercise for building the quads in those who can perform them pain-free, have good strength symmetry, and devote time to training their hamstrings and glutes as part of a well-balanced training plan.

Be aware. If end-range knee extension causes pain, then avoid that range of motion. On the other hand, you may also change the setup of the leg extension machine and use a foam pad to increase range of motion at the bottom, and benefit from that hypertrophy stimulus.

Overall, exercises and training methods should not be labeled as “good” or “bad.” Context is always key. If you’re concerned with heavy leg extensions, aim for 15-25 reps performed close to failure. For everyone else, sets of 10-15 reps will generally work best.

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  1. Ebben, W., Feldmann, C., Dayne, A., Mitsche, D., Alexander, P., & Knetzger, K. (2009). Muscle activation during lower body resistance training. International Journal of Sports Medicine, 30(1): 1-8.
  2. Stensdotter A., Hodges P., Mellor R., Sundelin, G., Hager-Ross, C. (2003). Quadriceps activation in closed and in open kinetic chain exercise. Med Sci Sports Exerc, 35(12): 2043-7.

What is your opinion of doing single leg reps on leg extensions?


Big fan. Especially for those with left-right strength/size differences. A few other techniques I like with leg extensions:

  1. 2/1 eccentric technique: Raise with both legs lower with one
  2. Iso-dynamic: Isometric hold for 10-30 seconds at the top followed by standard reps.
  3. Leg extensions with pauses: Hold each rep at the top for 2-3 seconds.
  4. “Isometronics”: Full reps, 7-10’s iso hold at the top, then bottom-half partials to failure. The isometric can also be done at the start and before the full reps.

Hope that helps :+1:


I had surgery for my Patella tendon and my surgeon made sure I understood to stay away from leg extensions. One of the worst exercises you can do if you have that injury.

It depends what stage of the healing process you were in. For late stage rehab leg extensions are actually used successfully quite often by PT’s. In scenarios like that, using lighter leg extension loads coupled with blood flow restriction training can be very effective.

It’s all context-dependant of course, and I’m sure at that stage you were given great advice. But, for some of the reasons highlighted in this article they still have a place for rehabbing cranky knees :slight_smile:

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This was immediate post surgery.

I do use them now but I don’t go heavy or lock out, I just feel it’s too much of a stressor on the knee. This of course is my experience and opinion.

Thank you for the insight :+1: Hope the knee is back to full capacity!

What Gareth_Sapstead stated. Also, having done weight training for 47 years, arthritis has overcome me, impacting my leg workouts. I do only Leg Presses, Leg Extensions, and Seated Leg Curls now. If our Purple Gym would get more leg machines, I’d use them too.

Use the toes in, toes straight, and toes out positions for some fun. Additionally, as you noted, doing one leg at a time on the equipment might create variety, but maybe help equalize the load when using both legs.

To longevity,

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Couldn’t agree more!

Big thanks from Cape Town South Africa. I remember while I was still on instagram following your account, I made a nasty comment about the background music was on one video. Gareth asked what about it, I responded that its too loud…I expected a nasty comeback and this fellow simply improved the sound quality on his videos AFTER. I learned the true meaning of taking criticism constructively and this shows you take fitness and sharing all these tips with us seriously. Thank you again!

I’m always open to hearing thoughts and ideas in how I might better my delivery of things. So always feel free to throw ideas my way for videos and article topics :slight_smile:

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Really helps! Thanks Gareth!!

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Great! You’re welcome!