The aim of this study was to evaluate the intra- and inter-examiner reliability and validity of neck range of motion (ROM) measurements. Thirty-five healthy subjects were assessed in all neck movements from two initial positions, sitting and standing, actively (open and closed eyes) and passively by using a 3D ultrasound-based motion analysis device (Zebris). Three tests were employed to assess intra-examiner reliability and two examiners used for the inter-examiner reliability. X-rays in neck flexion and extension were used to validate the Zebris system. The standing position yielded higher intraclass correlation coefficient (ICC) values (>0.86) with less error [smallest detectable difference (SDD)<13.8%] than sitting (ICC>0.79, SDD<14%). Passive assessment of neck ROM presented better reproducibility than active assessment with open or closed eyes in both positions. The inter-examiner reliability was moderate (ICC=0.43-0.68). The correlation between the Zebris system and X-rays was high in both flexion and extension movements. The results showed that the most reliable protocol for assessment of neck ROM is a passive measurement in the standing position. The measurements were well validiated against X-rays and the experience of the investigators must be considered before any comparison among studies is employed.

The Greek FES-I was valid, reliable, comprehensible and acceptable for the sample tested and may thus, be used in cross-cultural rehabilitation research and practice.

1b.

Visual control of postural sway during quiet standing was investigated in normal subjects to see if motion parallax cues were able to improve postural stability. In experiment 1, six normal subjects fixated a fluorescent foreground target, either alone or in the presence of full room illumination. The results showed that subjects reduced body sway when the background was visible. This effect, however, could be mediated not only by parallax cues but also by an increase in the total area of visual field involved. In experiment 2, other parameters such as image angular size and target distance were controlled for. Twelve subjects fixated a two light-emitting diode (LED) target placed at 45 cm from their eyes in a dark room. A second similar two-LED target was placed either at 170 cm (maximum parallax) or at 85 cm (medium parallax) from the fixated target, or in the same plane of the fixated target (0 cm, no parallax). It was found that the amplitude of sway was reduced significantly, by approximately 20%, when the two targets were presented in depth (parallax present) as compared to when they were in the same plane (no parallax). The effect was only present in the lateral direction and for low frequency components of sway (up to 0.5 Hz). We confirmed in experiment 3 on eight subjects with a design similar to that used in experiment 2 that the effect of motion parallax on body sway was of monocular origin since observed with monocular and binocular vision. Geometrical considerations based on these results support the existence of two modes of visual detection of body sway, afferent (retinal slippage) and efferent (extra-retinal or eye-movement based).