Posture is defined as a balance in musculoskeletal system that involves a minimal amount of stress and strain on the body. Any deviation from this normal alignment results in a system of imbalance or abnormal strain on the musculoskeletal system. Excessive stress or strain on the musculoskeletal system leads to postural abnormalities. Musculoskeletal disorders are also known as cumulative trauma disorders, overuse syndrome and repetitive stress injury or repetitive strain injury. These are caused due to excessive forced repetitive movement, awkward posture or prolonged static posture and vibrations. Work related musculoskeletal disorders become hazardous when the tissue loading exceeds its anatomical and physiological limits therefore there should be awareness and better understanding of risk factors. The International Ergonomics Association defines Ergonomics as “The scientific discipline concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance”. Ergonomic risk factors are most likely to cause or contribute to an MSD.

            A recent survey which was conducted in Europe reported a high prevalence of musculoskeletal disorders among microscope workers. These investigators found out risk factors such as the working hours using microscope, duration of work without breaks and poor workstation ergonomics which were associated with symptoms. The most prevalent problems in microscope users are eye pain, neck pain, headaches and backache. While viewing the specimen in conventional microscopes the microscopist maintains a flexed neck posture from this view point of biomechanics there is changes in the length tension relationship in the cervical muscle, fatigue and pain.

           According to international association for the study of pain defines neck pain “pain perceived as arising from anywhere within the region bounded superiorly by superior nuchal line and inferior by an imaginary transverse line through the tip of first thoracic spinous process and laterally by sagittal plane tangential to the lateral border of neck.

            Poor head posture results in neck pain. Forward head defined as the protrusion of the head in sagittal plane so that the head is placed anterior to the trunk. Forward head posture eventually leads to shortening of posterior cervical muscles and weakening of anterior cervical flexor muscles. A specific impairment consists of motor -control deficits of cervical flexor muscles, which results in reduced activation of the deep cervical flexor muscles and overactivity of the superficial flexors eventually leading to fatigue and discomfort. If the forward head posture is maintained for every long time the shortening of the posterior cervical muscles leads to increase load on the noncontractile structures as the fascia and the connective tissue and exerts the abnormal stress on the posterior cervical structure leading to myofascial pain.

            The cervical flexor muscle, mainly the deep neck flexors longus capitus, longus colli, rectus capitus anterior and lateralis function to stabilize the spine. However, in cervical disorders the tonic holding capacity is less in these muscles. Neck pain is considered as chronic if it lasts for more than 3 months. Chronic neck pain symptoms have a large impact on function and QOL. Many clinical tests have been done for subjects with neck pain which focuses on assessment of neuromuscular control and function such as strength and endurance of deep neck flexors and extensors. Patients with chronic neck pain may tend to develop increased cervical lordotic posture associated with a forward head posture. Patients with chronic neck pain may tend to develop increase increased cervical lordotic posture associated with forward head posture. It is suggested that forward head posture leads to increase in the compressive forces on the cervical apophyseal joints and posterior part of the vertebra and to changes in in connective tissue length and strength resulting in pain

            Jull et al found out that muscular performance for the deep neck flexors was reduced in group of patients who had cervical headaches. She had developed a low load craniocervical flexion test to investigate the anatomical action of deep cervical flexors, specifically of the logus colli in synergy with longus capitus. Pressure biofeedback unit provides feedback and direction to the patients to perform the required five incremental stages of the test these incremental changes in pressure can be used as an outcome measure, serving as a reference point during deep cervical flexor re-education and training. The CCFT test is a clinical test asses an individual’s ability to slowly perform and hold a precise upper cervical flexion without flexion of the mid and lower cervical spine. It is based on the anatomical interrelated action of the deep muscles to support and stabilize the cervical spine. Patients with poor activation capabilities of their deep neck flexors may use substitution strategies to achieve contraction common substitutes include recruitment of superficial flexors, sternocleidomastoid, platysma and the hyoid. The test is stopped indicating the deep cervical performance is poor.

             Cervical posture has been evaluated by measuring three angle using photogrammetry they are Craniovertebral angle, cervical inclination angle, inclination angle of head. The three angular measurements are angle between C7, the tragus of the ear and horizontal; the angle between the tragus of the ear, the eye and the horizontal; the angle between the inferior margin of right and left ear and the horizontal. These angles were analysed using kinovea software. An angle less than 50⁰-53⁰ indicate forward head posture.

              Since microscopists are the most vulnerable group maybe prone to postural neck pain disorders due to faulty posture maintained while viewing the microscope. Very few studies have been conducted to understand the relationship between head posture and performance of deep cervical flexor muscles. Hence this study aimed at bridging that gap. The findings of this study could be used to prevent these problems by providing ergonomic advice to the subjects.

OPERATIONAL DEFINITIONS:

Activation Score: The activation score is defined as the maximum pressure (in millimetres of mercury) achieved and held in a steady manner for 10 seconds above the baseline pressure (20 mmHg), without any substitution strategy in craniocervical flexion test (CCFT). 

Performance Index: A performance index was calculated by multiplying the target pressure achieved (activation score) by the number of successful repetitions

Neck Pain: Pain perceived as arising from anywhere within the region bounded superiorly by superior nuchal line, inferior by an unoriginally transverse line through the tip of first thoracic spinous process, and laterally by sagittal plane tangential to the lateral border of neck

RESEARCH QUESTIONS

Is there any correlation between the head posture and performance of deep cervical flexor muscles in microscope users?

ALTERNATIVE HYPOTHESIS (H₁):

There is a correlation between the head posture and performance of deep cervical flexor muscles in microscope users

NULL HYPOTHESIS (H₀):

There is no correlation between the head posture and performance of deep cervical flexor muscles in microscope users.