We present our study of the influence of the head 30 degrees flexion position on the changes in the muscle strength of the upper extremities. This position is typical for a person working in front of a computer.The study involved 100 healthy volunteers and was performed at the Department of Morphology in Riga Stradiņš University, Riga, Latvia. For measurements we have used the MicroFET2 Hand Held Digital Muscle Tester to determine the strength of the muscles of the hand and the arm (M. deltoideus, M. biceps brachii, M. triceps brachii, M. abductor pollicis longus). The results of measurements were then used to analyze the difference in the strength of the muscles innervated by the spinal cord cervical region (C5-C8 nerves) for the same person sitting in the vertical position and sitting with the head flexed at 30°.The results of our study support the hypothesis that the changes in the strength of the measured muscles are related to the mechanical distension of the spinal cord, which leads to changes in spinal cord's blood supply. The kyphosis position of the cervical spine during head flexion at 30°extent shows Papers on Anthropology XXVI/1, 2017, pp. 115-125 116 | J. Vetra, V. Sklarevich, G. Anoufriev et al. that in the spinal cord segments C5, C6 and C7 are form mechanical distension, but the changes in segment C8 were not detectable.Using our statistical study, we can conclude that there is strong relationship in the strength change in most of the observed muscles between the vertical position and the flexion of head at 30 degrees.

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We present our study of influence full cervical flexion position on the changes in muscle strength of the upper extremities. This position is typical for a person working on mobile phone or iPad. The purpose of the study was determination of the connection between change of the head flexed position and changes in upper extremity muscles strength. The present study involved 80 healthy volunteers and was performed at the Department of Morphology in Riga Stradins University, Riga, Latvia. For measurements we have used the MicroFET2 Hand Held Digital Muscle Tester to determine the strength of the muscles of the hand and arm (M. abductor pollicis longus, M. biceps brachii, M. triceps brachii, M. deltoideus). The results of measurements were then used to analyze the difference in the strength of the muscles innervated by the spinal cord cervical region (C5–C8 nerves) for the same person sitting in the vertical position and sitting with the head flexed maximally. The results of our study support the hypothesis that the changes in the strength of measured muscles are related to the mechanical distension of the spinal cord, which leads to changes in spinal cord's blood supply. The kyphotic position of the cervical spine during head flexion shows that in the spinal cord segments C5 and C7 are formed mechanical distension. Using our statistical study, we can conclude that there is strong relationship in the strength change in some of the observed muscles between vertical position and full flexion of head

Background: Technology is prevalent in almost every aspect of life, from handheld phones to computers. Increases in cervical flexion can cause a strain on the neck and muscles of the upper extremity. Objective: To examine the effect of 30 minutes of cervical flexion at 45 degrees. It was hypothesized that muscle strength will decrease after flexion, and there would be no significant differences between dominant and nondominant arms or genders. Study design: Twenty-four participants (12 male, 12 female) (n = 24; height = 173.1 + 9.3 cm; weight = 73.33 + 22.58kg) were measured before and after cervical flexion using a MicroFET2 Hand Held Digital Muscle Tester to test the middle deltoid, biceps brachii, and triceps brachii of each arm. Results: Compared to pre-measures significant differences were found in both middle deltoids and both biceps brachii, but not in either triceps brachii (p < 0.05). Overall no limited significant differences were found between genders of muscles of either arm. Significant differences (p < 0.05) were found in the dominant biceps brachii, non-dominant biceps brachii, dominant triceps brachii, dominant deltoid, and non-dominant deltoid. Conclusion: These results suggest that a normal daily degree of cervical flexion will decrease some upper extremity strength over the course of 30 minutes.