Could you explain to me why quad function could be lost on either side as a result of a left AIC or PEC and how re-establishing a neutral zone of transition can allow us to regain quad girth and function? I recognize it has to do with general length-tension dynamics, but could you specifically explain why positionally the quad is at a disadvantage in the above patterns?
In the L AIC pattern, the L pelvis is in a position of flexion, abduction, and external rotation. The sagittal position of flexion (anteriorly tipped pelvis) is the problem for the quad. This position places the L quad in a passively shortened state. As a result, the rectus femoris becomes hyperactive during inappropriate times, such as heel strike and mid stance.
The L vastus intermedius is asked to contract all the time because the position of the pelvis inhibits the hamstring (because it's now too long) and gluteus maximus (because it's now too short). In the interest of not falling over, the vastus intermedius is asked to work with the rectus femoris to pull the COM forward as the hip extensor group is lost.
The L vastus lateralis becomes leveraged as the "accidental gluteus complex" to attempt to generate some frontal plane activity, but it is a poor femoral rotator and abductor. Since the body has no choice, the vastus lateralis is overworked to perform the incorrect jobs of FA IR and FA ABD.
Essentially, the entire quad group is in a shortened state and is overworked. The hamstring, gluteus max, anterior gluteus medius, piriformis, adductors, and deep rotators of the hip are effectively inactive due to either being habitually too long or too short. Unless the pelvis is able to move from the position of AF ER into AF IR to alter these length-tension relationships, the quads are the only muscles of the thigh that can work, so they become overworked. The result of this forced hyperactivity of the quads can result in what appears to be weak quads; the quads aren't weak, they are overworked and get fatigued and need a break.
If the pelvis is able to be moved into AF IR (extension, adduction, and internal rotation) the quad muscles are now in a lengthened state, and they will need to be re-trained to learn how to work in conjunction with a fully functional hamstring, gluteus complex, and adductor group from a lengthened state. That's why many people appear to have weak quads after they have been repositioned. The quads literally have not been asked to work from a lengthened state with other leg muscles contributing properly in a long time.
Personally, I don't really pay attention to quad girth because you can get a lot of girth that is phony. Just because someone has a large thigh circumference doesn't mean they know how to use it, or are using is properly. I'm much more interested in function than muscle girth because of how easy it is for a muscle to become hypertrophied while either performing the wrong job, or the correct job at the wrong time with the wrong co-workers.
I want to make sure I have this right for the right quad. In a L AIC, it appears weak because it is in a positionally lengthened state at the rectus femoris and sartorius and does not know how to contract and coordinate from a shortened position. Or would you expect to see more of a hypertrophied quad on the left with an actually normal right quad? Could you please clarify this for me?
Yes, the right quad is in a lengthened state and is perpetually asked to contract from a lengthened state. Any muscle that is consistently asked to contract without the muscle actually getting shorter at the proximal attachment site can appear to be weak just because of its position. In the L AIC pattern, the muscles on the R side that are accessible are early to mid stance muscles, and the muscles for late stance and push off are less accessible because of the lack of pelvic movement.
Once again, I don't really look at quad hypertrophy because from my experience, it's not an accurate reflection of function. However, due to the L AIC/R BC and their influence on our COM, we are likely to spend more time on the R leg as a general statement. That alone can cause any muscle to become hypertrophied on the R side. It doesn't mean the muscle is functionally superior or better at its job; it's merely because our COM is positioned on top of our R calcaneus. If I do happen to note that the R thigh is bigger, my goal is not to make the L thigh as big as the R one. My goal is to improve the functional performance of the entire R and L side so they work together as teammates for walking and breathing.
Personally, I'm not sure you can assign hypertrophied muscles as a clinical assessment of the AIC or BC patterns. Which muscle the brain decides to use as its best option to move the body through space incorrectly and with compensation varies person to person. I can't tell you in the L AIC pattern you will see a larger L quad or a larger R quad because it varies person to person.
If there is one thing I have learned over the course of nearly 20 years in PRI is to never trust your eyes. The tests don't lie; your eyes do. If anyone is attempting to assess patterned behavior based on what they see or palpate, their assessment will be incorrect the overwhelming majority of the time. The most common question I get is some version of "how do I get better at PRI?" My answer is to get better at performing and interpreting the tests. They tell you everything you need to know and how to proceed with any client or patient.
The people who struggle with the application of PRI concepts often rely on what their eyes and fingers tell them. I'm sorry, but our eyes and palpation skills are not accurate enough to determine the neuromechanical influence that patterned respiration has on our musculoskeletal system. Thanks for the great questions!