Forward head posture assessment

The forward head and shoulder angles were measured using photogrammetry of the sagittal plane. This method favoured reliability (ICC ranged from 0.88 to 0.98), and it has been used in various research^4,25,32,33. Forward head posture was defined as a cervical angle < 50°^15–17. A lateral-view photograph was taken to identify cervical angles in a standing position^15–17. Three anatomical signs, including left tragus, acromion, and the spinous process of C7-vertebra were determined and marked to measure the angles. Then, the subjects were asked to stand at the designated area beside a wall (at a 23-cm distance) so that their left side was placed toward the wall. The photographic tripod supporting the digital camera was placed at a distance of 265-cm, and its height was set based on the subject’s right shoulder level. In such circumstances, the subjects were asked to lean forward three times and raise their hand over their head three times. They were then asked to stand in a completely relaxed and natural posture, and to look at an imaginary point on the opposite wall (eyes in line with horizon). The tester took images of the body profile view after a five-second pause. Finally, these images were transferred to a computer, and the angle of the line connecting tragus to C7-vertebrae, and that of the line connecting C7 and the acromion process were respectively measured with the vertical line (forward head and shoulder angles) using Kinova software (Kinova-0.8.27-64-bit, Kinova company, Canada)^34,35.