The semispinalis muscles are a group of three muscles located in the back of the cervicothoracic spine. These large and long muscles are involved in rotation, lateral flexion and when acting bilaterally extend the head and neck as a unit.
The semispinalis cervicis together with the semispinalis capitis are powerful neck extensors. When training it is important to note that these muscles are strongest in the neutral position. Starting a neck extension exercise with the neck flexed does not allow you to utilize the weight that these muscles are capable of moving. Take advantage of the neutral position when training on the Pendulum 4 or 5 Way Neck Machines to Get these powerful extensors Strong.
Starting Neck Extension from Neutral on the Pendulum 4 Way Neck Machine