The Effect of Physical Exercise Training on Neck and Shoulder Muscle Function Among Military Helicopter Pilots and Crew:
A Secondary Analysis of a Randomized Controlled Trial

Source: https://pmc.ncbi.nlm.nih.gov/articles/PMC7719717/

Exercises included:
Upper cervical flexion/extension from a supine position, and cervical rotation against mild resistance. (used elastic training bands for resistance
Conclusions:
Specific exercise training targeting the neck and shoulder muscles significantly improved MVC and RTD in the upper neck extensors of participants in the ETG.

Some examples of extensive studies on resistance training techniques.