The 30kg head position
I am sure everyone has seen someone with upper cross syndrome (UCS), whether they knew what it was called or not. A person with UCS will look like they are hunched over with rounded shoulders and head protruding forward. See the image below to get a better visual of what UCS looks like.
Basically, if someone has UCS they will have tight (overactive) upper traps and levator scapula muscle as well as tight chest muscles. Along with these tight muscles, the neck flexors on the front side and the rhomboids and lower traps on the back are weak. The tight or over-active muscles have become shortened and the weak or under-active muscles have been lengthened. This is what happens when there is a muscle imbalance in the body.