Sore neck muscles most likely indicate too much flexion and/or extension in the cervical spinal column (neck) during load carrying or repetitive movements. Looking down at your feet during hiking or staring too far down or up the trail both place your neck in a position that is not natural and will more often than not lead to neck pain or worse. I've had neck pain due to my tendency to stare down at my feet while hiking, running, or walking (excessive extension). Every time I went on a long hike my neck was sore the next day. After realizing what I was doing wrong I decided to re-train myself to look several feet in front of me and use my peripheral vision to mind my footwork. Only if the footing got tricky did I look down. Hope this helps.
