The neck is made up of flexor muscles in the front and extensor muscles in the back. When you look up at your partner while belaying or climbing, your neck extensors are constantly overworking. Over time, these muscles get strong and stiff while the neck flexors become weak, creating an imbalance. This imbalance can also lead to compression of the joints in your neck. You should be aware of the dangerous movements that can increase the stress on the neck and eventually lead to pain and injury. These movements are likely from poor belaying postures such as a backward-tilted neck, slumped spine and forward shoulders.