The purpose of this paper is to assess the reliability, validity and usefulness of three outcome measures: cervical ranges of motion, sagittal neck muscle strength and presence or absence of the flexion relaxation phenomenon (FRP) in the neck. The literature search included the Index Medicus and computerized database of MEDLINE for relevant material. Articles were selected if they contained primary data on neck range of motion, sagittal muscle strength and FRP. The results of 59 articles and 2 textbooks were analyzed. Normative values of cervical ROM have been reported in healthy subjects ranging in age from 18 to 74 years. The extent of degrees of motion lost per year did not differ between male or female subjects, but females started with higher degrees of active range of motion, which they maintained throughout life. Instrumented methods of recording muscle strength have included strain gauge dynamometers and modified sphygmomanometers. Parameters such as gender, age and stature were also observed to have important effects on muscle strength. The ratio of extension to flexion maximum isometric peak force has been estimated to range between 1.40-1.70 in normal subjects. Therefore, the extensor muscles of the neck are approximately 40% stronger then the neck flexor muscles. Evidence suggested that neck pain sufferers have weaker neck flexors than normal subjects. The FRP refers to the absence of myoelectrical activity in extensor muscles upon full forward flexion and has been documented in the cervical spine of asymptomatic subjects. In conclusion, inclinometric methods used for measurements of cervical range of motion were found to be safe, effective and reliable. The Cervical Range of Motion Device appeared to be well suited for clinical practice. The ratio of cervical extension-flexion maximum isometric voluntary contraction has been determined in asymptomatic subjects. The presence of the FRP in the neck has also been observed in normals. Future study is needed to investigate the functional limitations relating to acute and chronic mechanical neck pain which account for a portion of total neck disability.
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