Abstract
Prolonged computer work and smartphone use can cause stiffness of the neck and shoulder muscles, including the trapezius muscle. Hence, muscle hardness quantification is clinically beneficial. The present study aimed to examine the reliability of trapezius muscle hardness measurement using a portable muscle hardness meter and ultrasound strain elastography. Overall, 20 healthy young men participated in this study. Prior to measurement, the participant’s subjective symptoms, particularly shoulder muscle stiffness, were rated using an 11-point verbal scale. Furthermore, hardness of the right and left upper trapezius muscles was assessed. In the strain elastography assessment, muscle hardness was evaluated using strain ratio. Results showed that, in quantifying upper trapezius muscle hardness, both portable muscle hardness meter and strain elastography had an excellent intra-tester reliability (>0.9). However, the correlation coefficients between muscle hardness values assessed using a muscle hardness meter and those evaluated with strain elastography did not significantly differ, and the scores for subjective shoulder stiffness did not correspond to muscle hardness values. Therefore, the hardness of the trapezius muscle does not directly reflect the subjective shoulder stiffness. Future studies should thoroughly examine the location of the shoulder stiffness, and check whether it is accompanied by local pain or tenderness.
Highlights
In the recent years, neck and shoulder pain has become a common symptom due to prolonged intensive computer work [1,2]
Based on the correlation analysis, the correlation coefficients between the muscle hardness values assessed with a muscle hardness meter and those evaluated with strain ratio did not significantly differ (Figure 3, right side: rs = 0.014, p = 0.955; left side: rs = −0.085, p = 0.720)
This study examined the reliability of trapezius muscle hardness value assessed using a portable
Summary
Neck and shoulder pain has become a common symptom due to prolonged intensive computer work [1,2]. 2019 of the Ministry of Health, Labor, and Welfare, shoulder stiffness is the second most common complaint (57.2 per 1000 population) after back pain among men and is the most frequent condition (113.8 per 1000 population) among women [3]. Previous studies have shown that individuals with neck or shoulder pain have stiff trapezius muscles [4,5]. Those with muscle stiffness are more likely. Trapezius muscle hardness should be quantified to obtain clinically useful information and assess the effect of therapeutic interventions. Studies on muscle hardness using a push-in muscle hardness meter have been conducted for a quarter of a century [8,9,10]
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