Maximal isometric muscle strength of the cervical spine in healthy volunteers

Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hung Hom.
Clinical Rehabilitation (Impact Factor: 2.24). 11/2002; 16(7):772-9. DOI: 10.1191/0269215502cr552oa
Source: PubMed

ABSTRACT To describe the maximal isometric neck muscle strength in healthy Chinese volunteers, in six different directions, as measured by a Multi Cervical Rehabilitation Unit.
A standardized cross-sectional observational study.
A university rehabilitation unit.
Ninety-one healthy volunteers aged 20-84.
During the measurement the subject was instructed to do three consecutive steady contractions as hard as possible, with a 10-second rest in between each contraction and a 2-minute rest between different directions. The peak isometric strength for each of the six directions (flexion, extension, lateral flexions, protraction and retraction) was calculated.
No significant difference was found in muscle strength between different age groups. Isometric muscle strength in the direction of right lateral flexion was significantly greater than that to the left in men (p = 0.030), but no difference was found in women (p = 0.297). Isometric strength in all directions in men was 1.2-1.7 times that in women (all p < 0.028). Correlations between physical measurements (height and weight) and strength values were all insignificant in both genders.
Men have approximately 20-70% greater isometric neck muscle strength than women. Both men and women can maintain high levels of cervical muscle strength in six different directions up to their seventh decade. There is no significant correlation between physical measurements and isometric neck muscle strength.

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    • "In addition, only few studies have examined the influence of gender [1] [5] [8] [27] that has been demonstrated for other joints such as the knee [18]. For instance, authors [5] [8] reported no significant differences between men and women when comparing flexor/extensor ratio at any angle of flexion or extension. "
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    ABSTRACT: The aim of this study was to compare maximal isometric torque and EMG activity of neck flexors and extensors in flexed and extended positions between men and women. Twenty four non-trained young healthy subjects (12 men vs. 12 women) performed maximal isometric neck flexion and extension within 30◦ around the neutral position in a sitting posture using a modified isokinetic dynamometer. Surface EMG activity of sternocleidomastoid, scalenus, paraspinal and upper trapezius muscles was recorded bilaterally. Men exhibited higher normalized-to-lean body weight torque than women mainly during neck flexion (44%, P < 0.001) compared to extension (18%, P < 0.05). In addition, torque increased from extended to flexed positions in women only (+17%,P <0.001). This was associated with a decrease in EMG of neck extensors and upper trapezius muscles (from 35% to 20% and from 18% to 7%,P <0.001, respectively) without changes in agonistic activity of neck flexors with neck position. In contrast, men displayed similar torque and muscle activation level within 30◦ of range of motion around the neutral position for both directions. These findings demonstrate gender-specific differences in neck function that was probably linked to higher coactivation level in antagonist muscles (neck extensors) and stabilizers (upper trapezius muscles).
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    • "In these studies neck strength was measured in the neutral position only. Only a few studies have been published concerning the rotation strength of the neck muscles in healthy subjects (Ylinen et al., 1999; Vasavada et al., 2001; Chiu et al., 2002) and in patients with chronic neck pain (Berg et al., 1994; Bronfort et al., 2001; Chiu and Lo, 2002). The most significant reason for this has probably been the lack of reliable instruments with which to measure rotation strength. "
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    ABSTRACT: To characterize isometric rotation strength in the neutral and in different prerotated positions of the neck. This was a descriptive study involving maximal isometric strength measurements of the cervical musculature. 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. 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. 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. The present results show a clear relationship between the prerotated position of the neck and maximal voluntary strength in rotation. 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.
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