The main objective of this research is to asses the effectivity of action observation therapy, left/right discrimination and therapeutic exercise in the nociceptive processing of the cervical region.

Neck pain is the fourth cause of loss of years due to disability, behind back pain, depression and joint pain. Studies show that about half of the population will experience at least one episode of the clinically important neck during their life. The vast majority of studies indicate a prevalence of neck pain that varies between 15% and 50%, including a systematic review with a ratio of 37.2%, the investigators can ensure that neck pain is a common pathology among the population. Among the variables associated with neck pain, besides rheumatology, include genetic, psychopathological variables (such as depression, anxiety, coping skills, somatization), sleep disorders, smoking and a sedentary lifestyle, among others. All those variables alter the nervous system in a proprioceptive level, so that deep and superficial flexor, as well as the rest of the muscles, they do not receive correct information that prevents them from processing properly the obtained information. Therefore, alterations also occur at central nervous system levels as in the processing of pain and its control by inhibitory descending systems.

The most used treatment for neck pain is exercise. In a recent Cochrane review conducted by Gross A. et al., It has been proven, despite the shortage of high-quality studies, that the use of exercise routines based on strength and resistance training causes a reduction in pain.

Motor imagery (MI) or graduated motor imagery (GMI) is defined as "the mental and dynamic process of action, without real movement execution" and the action observation (AO) consists in observing an action carried out by another person. These treatments are based on the ability of the nervous system to assimilate the images seen and process them until they reach the motor cortex, and thanks to the mirror neurons, the painful pattern decreases until it disappears. Thus, visualising a painful situation provokes and evokes in the brain, a painful experience, even when this is not actually happening.

Therefore, the interruption of this neural network of cortical proprioceptive representations and integration of motor processes, also known as "body schema", is particularly relevant for movement and manual therapies. One way to measure the current state of the body scheme is through laterality tasks or "left / right judgement task" (LRJT), which have proven to be an effective and reliable tool and can also be used as a treatment.

All of the above facilitates the possibility of using these tools as treatments focused on the cortical area with GMI. However, the effectiveness of MI is controversial. Some studies have been carried out in pathological patients, in a pilot study they confirmed the changes produced in the neck region, both by an increase in the range of movement and an increase in the pain threshold to pressure, focused on the population with chronic neck pain. It is difficult to find studies in healthy patients, although in recent years some publications on motor imagery can be found finding changes in the descending inhibitory systems of pain and its processing. Many variables such as the duration of the sessions, the time per exercise or the type of tasks to be performed, together with the lack of studies on the neck region and the comparison between different tasks and their respective affectation of the descending pain inhibitory systems, have led us to carry out this study.

Inclusion Criteria:

• Healthy volunteers.
• Asymptomatic on cervical region.
• Understands and accept the informed consent.
• Spanish speakers.
• People with no cognitive disorders.

Exclusion Criteria:

• Pregnant women.
• Positive neurological signs or evidence of spinal cord compression (abnormal diffuse sensitivity, hyperreflexia or diffuse weakness).
• Previous cervical surgeries with recurrent symptoms.
• Previous headaches.
• Inability to provide informed consent.
• Cognitive disorders.
• Reading or verbal misunderstanding when receiving instructions.
• Having suffered any pain in the last 3 months, both in the quadrant suppressor as in the lumbar region and pelvis.
• Suffer any pain at the time of the study.
• Any recent traumatic event, whether physical or psychological / emotional.

Single blind