Simply put, the deep neck flexors are the equivalent of the core for the neck. When we think about our core, we often are referring to our abdominal muscles in the trunk. These mostly support our low back or lumbar spine. The good news is that we have similar supportive musculature for our neck - the deep neck flexors!
There are two main muscles that make up the deep neck flexor group: the longus capitis and the longus colli. In as lay terminology as possible, the longus capitis muscle attaches from the base of the skull to the front side of vertebrae from C3-C6 and the longus colli muscle runs along the front of the spine from C3 down to T3. Any rehabilitation that is focused on improving a forward-head / rounded shoulders posture or any rehabilitation from a neck injury should include some form of exercise for these muscles. The typical exercise is something we call the “chin tuck.” I often refer to this as “the sit up for the neck.”
The challenging part of this deep neck flexor group is being able to isolate and access it without recruiting other neck musculature. When you truly look at the anatomy of the neck, you can see that this deep neck flexor group is named such because it lies “deep” to the esophagus and trachea. This is where the challenge of access comes into play because there are many muscles that work easily but are “superficial” to the esophagus and trachea. These muscles are used for swallowing, talking, chewing, etc. So, in physical therapy, we need to teach our patients how to turn those muscles off and turn the deeper ones on!