Comparison of upper and lower trapezius muscle strength in female office workers with and without chronic neck pain.

BackgroundIn chronic pain patients, pain sensitivity and maximum voluntary contraction (MVC), a measure of muscle strength, are often impaired and related to the pain intensity. Therefore, this study aimed to assess MVC, pain sensitivity, and the potential association with pain intensity.MethodsA cross-sectional observational and analytic study with 133 female office workers was conducted, including both asymptomatic controls and those with chronic neck pain. The workers with chronic pain were categorized into pain conditions (chronic trapezius myalgia and chronic non-specific neck pain) and pain intensity groups, as mild pain (Visual analogue scale (VAS ≤ 3) and moderate pain (VAS > 3) groups. A handheld dynamometer was used to measure MVC at the upper trapezius (UT) and lower trapezius (LT). Pressure pain threshold (PPT) and temporal summation of pain (TSP) were assessed as measures of pain sensitivity.ResultsThe chronic trapezius myalgia group (n = 49) had a significantly decreased UT MVC [F (2128) = 4.099, p = 0.019] and LT MVC [F (2128) = 3.511, p = 0.033]. The moderate pain group (n = 43) had a significantly decreased UT MVC [F (2128) = 5.507, p = 0.005], and LT MVC [F (2128) = 4.119, p = .018]. Pain intensity, UT/LT ratio explained 19.4% of the variability in LT MVC, plus PPT explained 19.3% in UT MVC.ConclusionFemale office workers with CNP classified as moderate pain intensity and chronic trapezius myalgia had significantly decreased MVC in the UT and LT than the other groups. Pain intensity, decreased PPT in tibialis anterior, and the UT/LT ratio provide a limited explanation for muscle strength variability.