Last Update On January 11, 2012
Leg Curl - Functional?
by Vladi
The functional crowd has always hated on the leg curls and similar knee flexion exercises since the very beginning. I've read articles called “Leg Curls Are For Wankers” and so on and to be honest some time ago I would agree with something similar but not now.
The most used argument is: “Hamstrings are not supposed to be used without your glutes and other small hip extensors.”
How about NO ? First, anybody who thinks that the body is “supposed to” always perform in a certain way is either blind or plain ignorant. I understand that there are “natural” movements like walking, running, squatting and so on but the body can move in hundreds of different ways rather successfully. Acrobats, bboys, cirque artists, skaters, gymnasts and so on perform variety of movements that do not seem to be that “natural”.
What I'm trying to say is this: The body follows certain mechanisms but the variety of combinations formed by flexion and extension of the muscles in our body are endless. Saying that one muscle should always work with another one when if fact the very same muscle can perform isolated action by itself does not make any sense. If I can move that way it's “natural” otherwise I wouldn't be able to do it and will simply hurt myself.
Is it a crime to flex my knee without extending my hip?
According to the functional crowd the hamstrings are used most of the time as hip extensors rather than knee flexors and therefor should be trained using hips extension exercise mainly.
How about NO? Have you ever tried walking? Just try to walk/run without flexing your knee. How does it feel? To make my point even stronger I will go back to my tendonitis story. Years ago when I was in France for 1 week I used to walk and walk and walk and walk all of those 7 days. (Read the tendonitis story for more information). I was walking around 10-12 hours a day. Or more. It was hell. After 1-2 days I woke up with severe soreness right into my knee hamstring insertions. It was caused by the walking of course. I wasn't doing anything else. That's how I found out that the hamstrings tendons behind the knees are largely involved into walking.
What a shock !!!
In other words there is quite a lot of knee flexion during walking and running. You can't flex your knee with hip extension alone. Sorry. The truth is that knee flexion is just as important as hip extension and ignoring one for the other is just plain stupid. The fact that there is not active hip extension during leg curls does not make the exercise any worse. It's an isolation exercise designed for a specific goal - to target the hamstrings without the involvement of anything else. This can be very important if you have excessive hamstring weakness. For example squatting is quad and glute dominant exercise but does not do that much for hamstring as other more specific exercise like Romanian deadlifts, glute ham raises...etc. Therefor people relying primary on squats for their hamstring work will end up with weak hamstrings and may find the use of a hamstring exercise that does not involve the glutes like RDLs or Good Mornings useful. In other words if you have strong glutes and weak hamstrings how are you supposed to strengthen your hamstrings by using other exercises with over-involvement of the glutes? If the glutes are stronger they will always take over.
At the same time the very same functional trainers recommend the use of the glute-ham raise which is a great exercise but please tell me how is it more “functional” than a leg curl. When will you have to perform a glute ham-raise in “real” life?. This is a contradiction in my eyes because the glute-ham raise is mainly knee flexion as well. The bulk of the work is pure hamstring flexion and the knee joint is the only one that actually moves unless you use a specific glute-ham roman chair which a lot of people don't have access to and end up using the homemade version. As a person who has done both (leg curl and glute-ham raises) I don't see that much difference as far as pure hamstring work goes. Yes, glute-ham raises look quite cool and are very effective and tough exercise. They allow you to murder your hamstrings at home and are harder for most people. At the same time heavy leg curls will achieve quite similar effect on the hamstrings.
Bashing the leg curl is just wrong and shows nothing more than failure to understand its function - allow athletes to isolate their hamstrings over a great range of motion without involvement of other muscles in order to improve specific weakness. It's a great tool to have in case you need it.
In the meanwhile the functional crowd can think on this one:
I usually type on the computer using mainly my fingers without that much biceps and triceps involvement? Will this cause potential problems like: burning in hell and being sent to prison in order to become a functional person who uses all of his muscles all the time ?
Just kidding don't take it personally.
Good luck. Have fun.
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