Aloha my friends!
If you want strong, well-developed and defined quads (along with healthy knees), it’s essential to effectively work EVERY region of ALL of the quad muscles! And contrary to popular belief, each muscle is primarily responsible for different movements, and needs to be worked accordingly. You can find in-depth examples of how that applies to the vastus medialis (“inner” quad muscle) in one of my recent YouTube videos.
Today I want to highlight one of the MOST important of those differences, and it’s how to effectively work the rectus femoris!
The rectus femoris is the longest and second largest of the quad muscles, and runs down the center of the of the upper leg, inserting on the lower leg just past the knee. However, unlike ALL of the other quad muscles, the rectus femoris DOESN’T originate from the femur (upper leg bone)! Instead, it’s upper end originates from the PELVIS.
That means that it’s a BIARTICULAR muscle (crosses two joints – the hip and knee), and therefore as we discussed last week is susceptible to ACTIVE INSUFFICIENCY (see FTF Week 80).
So here’s the key point to understand!
If the HIP is in a FLEXED (aka bent forward) position, that shortens the rectus femoris at its upper end, rendering it unable to exert significant force in extending the knee at its lower end!! Especially during the second half of knee extension.
So if you are always doing leg extension exercises in a SITTING position, you are not adequately working the rectus femoris, resulting both in limited overall quad growth and in muscular imbalances that will eventually lead to pain and injury!
In order to work the rectus femoris (at least its lower region), you HAVE to perform knee extensions with your hip in a straight or mostly-straight position!! That means you either need to be lying flat on your back or standing up!
Both methods are used in my Hypertrophy Series Total Leg Programs. But here is an example of the standing technique using a cable machine:
In addition to the hip positioning, you also want to make sure that you’re extending your knee STRAIGHT down / forward rather than letting your leg rotate internally or externally, which would preferentially activate the vastus lateralis and medialis, respectively, over the rectus femoris.
Application: You NEED to integrate exercises that work knee extension with a STRAIGHT HIP in order to effectively work the rectus femoris!
Dr. Gains 
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