The leg extension exercise is the most common and widely used quadricep isolation exercise on the planet.
And, even though it does have potential for knee stress, especially when done too heavy, it CAN be an effective way to train the quads.
I'm not going to get into the pros and cons of the leg extension as an exercise here...this is all about how to do the exercise with a dumbbell, if you want to try it out and see how it feels to you.
This dumbbell version of the leg extension can be a potential solution for three problems...if you don't have leg extension machine, if you have a bad leg extension machine, or if you find leg extensions torque your knees.
You'll need a bench, a towel and a dumbbell...and that's it.
How to do Dumbbell Leg Extensions
Sit on the end of the bench with your dumbbell standing on end.
Wrap the towel around the handle, on top of your feet and under the top plates of the dumbbell. This is padding for your feet.
Set your feet so that they hook the top plates and your heels contact the bottom plates. This locks your feet into position.
Sit back until your knees are just over the end of the bench. Lean back and grip onto the sides of the bench.
If you're using a heavy weight, you may want to set a plate on the other end of the bench to counterbalance the load (you'll see the other end of my bench coming off the ground a bit during the exercise).
Now do a leg extension movement up.
This not only hits the quads strongly at the top with a hard contraction, it actually works the tibialis anterior (front shin muscles) isometrically as you hold the dumbbell in place. You're pulling with your toes and pushing with your heels.
Repeat for whatever rep range you're aiming for (this can be high reps or low reps).
Targeting Different Aspects of the Quads and Knee Issue Considerations
Even though, as you can see in the pictures, I'm leaning back and my toes are rotated inwards to hook the dumbbell, this doesn't affect what muscles in the quads get worked. Studies have shown that positioning doesn't matter in terms of muscle activation.
I also find that because the load is on the feet and your quads are working on it directly, it doesn't put torque on my knees like a machine often does. I find that happens when the rotating cam of the machine doesn't properly line up with the knee joint, creating shearing force in the knee.
With this method, it doesn't seem to be an issue.
Naturally, if you do have knee issues and find normal leg extensions a problem, either skip this one completely or start very light and assess how it feels.
Overall, this is a very effective and very simple way to perform a leg extension for the quads when you don't have a leg extension machine.
If quadricep development (and burn) is your goal, try barbell cursing walking lunges.
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Want more unique and challenging exercises to work your entire body with simple equipment? All you need is just a barbell, dumbbells and a bench. Check out The Best Home Gym Exercises You've Never Heard Of!
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