Understanding Under and Over active muscles (UA/OA) for the NASM CPT exam

It seems that almost everyone studying for the NASM CPT has had an issue trying to understand UA/OA. I myself had a lot of problems but found an easy way to understand the muscle groups. Before I get into it there are a few things I need to mention. You might not like what I am going to say however, you will thank me later for the tough love ūüôā

  1. This is not something you can memorize, before the exam so please do not try!!
  2. This is the foundation for you being a great trainer
  3. You NEED to practice this every day on yourself, a family member, a friend or by performing assessments on every single person you can get your hands on prior to the exam.

One of the domains covered of the NASM CPT exam and study material is Posture and Movement Assessments covered in Chapter 6. In my opinion one of the most important things to understand, because it is our job as trainers to properly assess clients so we can design the best training program as possible.

It is extremely critical that we understand muscle imbalances. To break it down at a basic level think about it like this.

  1. Overactive muscles receive too much signaling from the CNS
  2. Underactive muscles do not receive enough signaling from the CNS

The postural dysfunctions we are looking for are when working with our clients are:

  1. Pronation Disorder Syndrome –¬†The feet are turning outwards, foot pronation (flat feet), and adducted and internally rotated knees
  2. Lower Crossed Syndrome ¬†–¬†The lower back has a big arch (called anterior tilt of the pelvis)
  3. Upper Crossed Syndrome –¬†The head leans forward and rounded shoulders

NASM teaches us that we can use the postural assessments to identify movement compensation patterns caused by muscle imbalances when we work with our with clients. These are the most common assessment that are used.

  1. OHSA (Over Head Squat Assessment)
  2. Single Leg Squat Assessment
  3. Pushing Assessment
  4. Pulling Assessment

Let’s get in to the practical stuff now. Let’s break down each syndrome so you can do it and talk about it. This will help a ton!!

Pronation Distortion Syndrome – Possibly Overactive (tight muscles) are calf muscles, adductors, IT Band, bicep femoris.

In this example let’s take someone that wears high heels to work. While your heel is elevated upward in a (planter flexed) position you are causing the calf muscles to contract and this makes them become tight or overactive. Issues with the calf muscles can possibly alter joint movement of the feet. In the photo below you can see the muscles in action and what happens.

Photo Credit: walkwellstaywell

Now as I mentioned before if muscles are being overworked the opposite side muscles aren’t getting much attention and are left under worked.

Try this!

  1. Stand with you feet shoulder width apart
  2. Turn both feet outward.
  3. Turn your knees in slightly just enough for a visual

You will feel pressure in your calf muscles and in the outside muscles of your lower legs and knees.

Now look at your chart Table 6.9 and Appendix D (Muscular System) and say each muscles name as you touch each individual muscle. Start first with the tight muscles and  go through all of them, then move to the underactive muscles. Talk out loud to yourself as if you were explaining this to a client and telling them what you found. This will help a lot! You will start to see a pattern with certain muscles groups that work together as you work through each postural disorder.

For this disorder these muscles are running on the outside of the leg (the overactive muscles), and the inside of the leg (the underactive muscles). With regards to the knee joint the one exception is the (AD)ductor muscle group which runs on the inside of thigh. When the adductors become overactive they can pull the knee inwards. This is known as¬†Knee Valgus or “Knock Knees”.

Knock Knees
Photo Credit: NASM.org

To recap: if the outer leg muscles are shortened (contracted) or tight or overactive, this must mean that the inside of the leg muscles will be lengthened (stretched), or underactive. This causes a neuromuscular imbalance.

Lower Crossed Syndrome – Possibly Overactive (tight muscles) are the Calves, Hip Flexors, Pecs, Lats, Erector Spinae, Adductors.

In this example let’s take someone that that is sitting at a desk all day long. When you sit for a prolonged period of time in seated / flexed position you are causing the hip flexor muscles to become tight or overactive.

NOTE: Hip flexion occurs when an individual decreases the angle between the femur (thigh bone) and the pelvis or lumbar spine. This can occur when an individual elevates the knee toward the abdomen (femoral-on-pelvic hip rotation). During this motion the pelvis and spine are fixed while the femur rotates.

See the source image
Photo Credit: spineandsportsmed.com

With that being said one of the biggest causes for hip flexion is when the Rectus Femoirs becomes overactive. This quadricep muscle crosses over the hip joint and is responsible for pulling the pelvis downwards (anteriorly rotated). Once this happens it becomes a chain reaction (reciprocal inhibition can lead to synergistic dominance) and cause the Gluteus maximus to become underused. The same thing will happen with the back muscles, they become overactive which causes the abdominal muscles to become lengthened and weak.

Photo Credit: Human Kinetics

Here I illustrate the hip flexors to give you a visual. I would refer to Appendix D (Muscular System) for the full list which maps to Table 6.9

Photo Credit: MMG

Let’s try this one out.

  1. Sit upright in a sturdy chair.
  2. Arch your tailbone backwards so you cause your pelvis to rotate anteriorly. This will cause a little pressure in the lower back and you can feel your abdominal muscles stretch.
    • NOTE: Just do this lightly so you get the picture. This can be painful for some people and I don’t want you to hurt yourself.
  3. Pull your shoulder blades together slightly and arch your upper back

This should allow you to physically feel the LPHC tilt. Now just like before look at Table 6.9 and Appendix D (Muscular System). Touch each muscle starting with the tight or overactive. Repeat each muscle name out loud. Once you have done this move on to the underactive muscles.

Upper Crossed Syndrome Summary –¬†Possibly Overactive (tight muscles) here are the upper traps, neck muscles, lats, chest and rotator cuff.

Photo Credit: Human Kinetics

In this example let’s take the same person that sits behind a desk all day typing on a computer. While they are sitting in the chair, their head over time will start to lean forward and their shoulders will become rounded / protracted or (internally rotated). This leads to all sorts of pain as you can see in the photo below.

Photo Credit: Bing.com

Now let try this last one!

  1. Sit upright in a sturdy chair.
  2. Put your hands on your knees while keeping your back straight. You will notice that when you do this while you are reaching forward towards your knees you will feel your shoulders internally rotate.
  3. Push your chin forward. While you do this you should feel some slight tension in the neck muscles. You can see that this is the major cause for people having headaches.
  4. Again refer to Table 6.9 and n Appendix D (Muscular System)

I will mention a few things that helped me out A GREAT DEAL before my exam, were finding the BrentBrookBush Institute. Dr. Brent is a former NASM Master Trainer and you can take his functional anatomy classes (1, 2 and 3). He will break down these concepts in super simple detail and you can also get CEU’s for his classes. Click here to get a referral

I also downloaded a great app from MuscleandMotion. It is a GREAT educational anatomy program which you can use on your computer and mobile device.

I hope this helps you connect the dots. If you have any questions please feel free to reach out to me.


  1. NASM CPT Study Guide
  2. NASM.org
  3. BrentBrookBush Institute
  4. National Foundation of Professional Trainers
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