Helping the function of trapezius are the splenius capitis and cervicis muscles. These two muscles are commonly injured with whiplash injuries due to car accidents. Pain and spasm in these two muscles lead to tension headaches and significant neck pain.

The person with problems in these two muscles have difficulty in bending the neck backward. There will also be significant pain on bending the neck sideways and also in turning the head to the painful side. Therefore when you see a person with difficulty in turning the head and neck to the left, consider problems with the splenius capitis and cervicis muscles on the left side and the right trapezius and vice versa. Such a person will usually have to turn the whole body since they have difficulty turning the head and neck. They will often complain that they have difficulty in driving due to difficulty in neck rotation.

The splenius capitis (head) muscle arises from the last cervical vertebral spine (C7) to the third thoracic spine (T3) and from the ligament between the spines known as the ligamentum nuchae to insert into the skull bone behind the earlobe known as the mastoid process.

The splenius cervicis (neck) muscle arises from the third thoracic to the sixth thoracic spines (T3-T6) and inserts into the transverse processes of the first through the fourth cervical vertebrae (C1-C4). Both muscles received nerve supply through the middle and lower cervical nerves.

Neck pain|shoulder pain: Role of deltoid

Neck pain and shoulder pain commonly arises from irritation of the C5 and C6 nerve roots. Both roots supply the deltoid muscle.

Deltoid has three portions namely the portion at the front of the shoulder (anterior deltoid), middle of the shoulder (middle deltoid) and a portion at the back of the shoulder (posterior deltoid). It arises from the front of the outer third of the collar bone, the acromion and the spine of the shoulder blade. It attaches to deltoid tuberosity on the arm bone (humerus). It is supplied by the axillary nerve which carries the C5 and C6 spinal nerve root fibers.

The anterior deltoid brings the arm up and forward (flexion), the middle deltoid moves the arm away from the trunk (abduction) and the posterior deltoid brings the arm backward (extension).
It is a powerful muscle in lifting type activities and also works constantly when the arm is outstretched to the front as in writing, typing, driving etc..

These forward motions of the arm known as shoulder flexion is performed by the contraction of many muscles which are large and powerful such as the pectoralis major, long head of the biceps, coracobrachialis and the anterior deltoid. To stabilize the flexion movement, the muscles that bring the arm backward (shoulder extension) have to undergo lengthening contraction. Shoulder extension is performed by three major muscles, mainly the latissimus dorsi, teres major and the posterior deltoid.

Pain, spasm and weakness of the poster deltoid is thus very common especially since C5 and C6 nerve root involvement is also very common. When the deltoid does not function properly, lifting type movements are performed by shrugging the shoulder, an action of the upper trapezius comes into play by . Since trapezius is not strong enough to perform lifting activities, the trapezius muscle goes into spasm and aggravating the neck and shoulder pain.

Therefore pain in the deltoid region cannot be localized to treating only the deltoid muscle. Selective activation using eToims Twitch Relief method must include all muscles involved in lengthening contraction supplied by the C5-C7 nerve roots and the entire length of the paraspinal muscles from the neck to the base of the spine.