Axial neck rotation strength in neutral and prerotated postures.

OBJECTIVE To characterize isometric rotation strength in the neutral and in different prerotated positions of the neck. DESIGN This was a descriptive study involving maximal isometric strength measurements of the cervical musculature. BACKGROUND The literature contains only a few studies pertaining to strength levels of the neck rotator muscles in the neutral position. None of these studies have dealt in detail with maximal neck strength in selected prerotation positions. METHOD Twenty healthy men volunteered as subjects. Maximal axial rotation strength of the neck muscles was measured in a neutral position and bilaterally at 30 degrees and 60 degrees rotation using the isometric neck strength measurement system. Isometric maximum voluntary contractions of the neck muscles in flexion and extension were also tested. RESULTS The highest strength values were not reached in the neutral position, but at the largest joint angles, while turning the head in the opposite direction from the prerotated position. Maximal strength increased with increasing angle, and at the 60 degrees prerotation angle it was 44% higher towards the right and 27% higher towards the left compared to the values obtained in the neutral position. The smallest strength values were also produced at the largest prerotation angles, but in the same direction. CONCLUSIONS The present results show a clear relationship between the prerotated position of the neck and maximal voluntary strength in rotation. RELEVANCE The data suggest that neck strength is highly prerotation angle dependent. Neck strength should be measured at several prerotation positions in addition to the neutral position in order to obtain the true strength values throughout the entire range of motion. Maximal neck rotation strength between subjects is differentiated best at the greatest prerotation angles.