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SUMMARYBackground. Fatigue is one of the factors causing disturbance in proprioception which can be manifested in two ways: general and local. Due to the important role of cervical proprioception on body stability and posture, research on the effects of general fatigue on proprioception helps to better understand its mechanism and to improve the strategies to prevent injury. Therefore, the aim of this study was to identify the effects of general fatigue on head and neck proprioception in young healthy adults.Material and methods. This clinical study was done by implementing pre-and post-test measurements in 112 young healthy subjects aged between 18-30 years and able to walk at a speed of 10Km for 5 minutes. They were randomly divided into an experimental and control group. The patients in the control (not exposed to a general fatigue task) and experimental (exposed to a general fatigue task) groups were matched for age, height and weight. In the first step, the zero absolute reposition angle of the head and neck was measured in all participants. Then the subjects in the experimental group did a five-minute run on the treadmill to achieve the level of general fatigue, following which the head and neck reproduction angle was measured in all subjects for the second time.Results. There was a statistical significant difference between pre-and post-test absolute angular error in the experimental group; however, there was no noticeable difference between the pre-and post-test data in the control group.Conclusions. 1. General fatigue increased the repositioning angular error of head and neck. 2. Neck proprioception decreased due to general fatigue. 3. General fatigue increased the risk of neck injury.

Background: Abnormal head and neck postures play a significant role in developing cervical spine dysfunction. Forward head posture (FHP) is one of the most common findings in individuals who experience head and neck disorders. Objectives: This study used a photographic method to analyze the head, upper neck, and lower neck postures in forward head posture in both static and quasi-static states. Since timely diagnosis and appropriate treatment are important in preventing further complications of this kinematic chain disorder, the postural variables of the head and neck were evaluated by focusing on their separate parts in both static and quasi-static states. Methods: This observational-analytical case-control study included 175 individuals with no history of neck pain in the past 6 months, 138 with FHP, and 37 with non-FHP. The postural angles, including the upper cervical, lower cervical, craniovertebral, head posture, and head tilt angles, were measured through photography in both the static state (with the head and neck in a neutral position) and the quasi-static state (while moving the head and neck in the sagittal plane) in a sitting position. The measurements were taken in two groups (FHP and non-FHP). Results: In a static state, the upper cervical angle was higher in the FHP group than in the non-FHP group. The lower cervical measurements were higher in the non-FHP group than in the FHP group. In the quasi-static state, significant differences existed in the changes of the upper cervical, lower cervical, craniovertebral, head postural, and head tilt angles between the two groups (P-value < 0.05). Conclusions: During full flexion to full extension of the neck, subjects with FHP exhibited reduced mobility in the cervical spine, particularly in the lower cervical region. Additionally, the position of the head relative to the neck remained unchanged in this group.

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