Assessment of stiffness of the superficial neck muscles in female office workers with impaired endurance of deep neck flexors: a case-control study

Introduction
The objective of this study was to assess the muscle stiffness parameter in the sternocleidomastoid (SCM) and upper trapezius (UT) in a group of office workers who did not attain the norm in the deep endurance flexor test (DEFT).

Methods
In this case-control study, the myotonometric muscle stiffness parameter (MyotonPro, Tallin, Estonia) was compared in the SCM and UT muscles in a group of female office workers who were unable to achieve the norm in the DEFT, i.e. the research group (RG), in comparison to the control group (CON) who attained the norm during the test. Subjects were matched in terms of their gender, age, BMI, nature and duration of their work, as well as the pain intensity and craniovertebral angle.

Results
Subjects in the RG had significantly higher stiffness of the UT (by 8.8%, 291.4 ± 36.5 in RG and 265.9 ± 25.6 in CON; p = 0.015, t = 2.29) and SCM (by 7.3%, 291.4 ± 36.5 in RG and 265.9 ± 25.6 in CON; p = 0.37, t = 1.85) myofascial tissue in comparison with the CON. The magnitude of the effects of the stiffness of the tested muscles on the results obtained by DEFT was stronger in the UT (Cohen’s d = 0.82, large effect size) than the SCM (Cohen’s d = 0.61, medium effect size).

Conclusions
The women who did not attain the norm in the DEFT had greater stiffness of the superficial UT and SCM muscles. Future studies should evaluate whether SCM and UT stiffness reduction therapy will improve the deep endurance flexor test results.