Some practitioners argue that text neck, military neck, and reverse C curve (Kyphotic). are caused by different reasons, but I explain to my patients that these changes are all induced by the same reason. Please watch the video (01:22) and see the below image for better understanding.

Even though your neck becomes a text neck due to weak core muscles, the neck curve would still look normal (C-curve). However, the neck extensors in the back of the neck do not want the neck to go further forward, so they start to pull it back by strongly contracting. This can change the curve into a straight line, which is often called 'military neck'.

This phenomenon does not get resolved by itself, but rather, gets worse as long as the root cause is still there. Weak core muscles create insufficient abdominal pressure (Root cause) -> Rib cage sinks down -> Neck extensors and spinal muscles are unnecessarily overactivated -> Military neck turns into the reverse C-curve.

As the normal neck curve changes from text neck (still normal C-curve) -> military neck (straight line) -> reverse C-curve, more pressure will be placed on the front of the disk, which can contribute to problems such as cervical disk herniation.