"Engage your quads". This is a common cue used by yoga teachers, but what does it mean? It refers to actively tightening the large quadriceps (quad) muscle on the front of your thigh. Your kneecap (patella) moves upwards toward your hip and your knee straightens as the quad contracts and becomes firm. Why is this important? Because it protects the knee from injury by making it more stable. The quads are also active when the knee is bent, keeping the knee from collapsing (think of bending the knees while lowering yourself into a chair, or walking downhill), but in yoga we often focus on the quads when the knee is straight.
First, a little anatomy. The quad is made up of four parts: vastus lateralis, vastus medialis, vastus intermedius, and rectus femoris. Part of the vastus medialis is referred to as the obliquus, or VMO for short. The VMO is important because the other parts of the quad tend to pull the patella outward; the VMO resists that pull, assisting the patella to stay in its groove in the center of the femur (thigh) bone. The patella moving outward is a common cause of knee pain. The VMO is especially active at the end range of straightening.
When the knee is straight and the quadriceps is relaxed, you should be able to manually move the patella freely up and down, and side to side. When the quad is active, the patella should stay put. Contracting the quad and stabilizing that patella is especially important in many of our standing poses: trikonasana, prasarita, uttanasana, and even tadasana. You do need to be careful to not hyperextend the knee though, which is straightening the knee too far back past straight. This is sometimes referred to as "locking" your knee joint. But that's a subject for another article!
Biofeedback using electrodes on the skin over the VMO can be used to measure the relative level of contraction of the muscle. Surprisingly, straightening the knees in plank pose while pressing the thighs up and pushing out through the heels is one of the best ways to activate the VMO. It's often that last little push into straightening the knee that gets the strongest contraction in plank and other active poses.
Keeping your quads strong is yet another way that yoga practice can help us stay healthy and active for a lifetime. Not only will they help you avoid knee pain and injury, but they also allow you to remain independent as you climb stairs, get into and up from chairs, and balance on one leg. We at Gudmestad Yoga recommend yoga for every phase of your life.
This article originally appeared in the Gudmestad Yoga Spring Quarterly Newsletter for 2019.