Final answer:
In a halfway lift, the neck should be kept neutral to maintain alignment and prevent strain, utilizing the muscles at the back of the neck to keep the head erect.
Step-by-step explanation:
In halfway lift, we want to focus on keeping the neck neutral. The center of mass of the head is not directly over the principal point of support, which is the atlanto-occipital joint. To maintain proper alignment and avoid strain, the muscles at the back of the neck should exert force to keep the head erect. This prevents the head from falling forward, much like when a person falls asleep and loses muscle tension. When performing a halfway lift, it is therefore important to engage the neck muscles properly to maintain a neutral spine and avoid unnecessary strain. Activating the neck muscles bilaterally will facilitate proper alignment of the head and neck during this exercise, much like the sternocleidomastoid muscle's role in head rotation and flexion as detailed in the described body mechanics.