Proprioception of the cervical spine in subjects with and without a history of neck pain

Background: Proprioception is considered to make an essential contribution to functional stability of a joint. It is thought that pain can reduce proprioceptive acuity and that this may promote joint pathology. Neck pain is a common musculoskeletal problem and to date there are few studies that have investigated its relationship with proprioception of the cervical spine. The purpose of this study was to determine whether a history of neck pain is associated with altered proprioceptive acuity of the cervical spine.Methods: Twelve subjects with, and twelve subjects without a history of neck pain aged between 17 and 45 years, were recruited from a university population. Subjects sat in a chair wearing a cervical range of motion goniometer (CROM) on their head. Target angles for proprioceptive testing were calculated for each subject at 25% and 75% of their total left and right cervical rotation. The subjects were then blindfolded and their head passively rotated to one of the target angles where it was held for ten seconds. The subjects actively returned their head to the start position and were then asked to actively reproduce this target angle nine times. Deviation from the target angle was recorded in degrees for each of the 9 repositioning attempts. This procedure was repeated for all four target angles. The mean error for deviations from each of the target angles were compared for the two groups using unrelated t- tests (normally distributed interval/ratio data) and Mann-Whitney U test (non-normally distributed interval/ratio data).Results: Neck pain subjects had a greater repositioning error than nonneck pain subjects. Mean errors for the four target angles were between 3.72 (SD=1.82) to 6.19 (SD=3.05) degrees in neck pain subjects and 2.39 (SD=1.70) to 3.61 (SD=3.55) degrees in non-neck pain subjects. The difference in mean errors was statistically significant (p<0.05) for the 25% and 75% left rotation target angles (p=0.025 and p=0.031 respectively) and the 25% right rotation target angle (p=0.020). Repeatability testing of the data collection procedure showed mean measurement errors of less than 1.0 degree. Conclusions: The results of this study suggest that the subjects with a history of neck pain had a significant reduction in the ability to reproduce specified target angles of cervical spine rotation. i.e. reduced proprioceptive acuity of their cervical spine. These results give impetus for further research into the relationship between neck pain and proprioception

Watermark detectors based on n/sup th/ order statistics

This paper deals with some detection issues of watermark signals. We propose an easy way to implement an informed watermarking embedder whatever the detection function. This method shows that a linear detection function is not suitable for side information. This is the reason why we build a family of non-linear functions based on n/sup th /-order statistics. Used with a side-informed embedder, its performance is much better than the classical direct sequence spread spectrum method.Anglai