Reliability of trapezius muscle hardness measurement: A comparison between portable muscle hardness meter and ultrasound strain elastography

Tomonori Sawada, Hiroki Okawara, Daisuke Nakashima, Shuhei Iwabuchi, Morio Matsumoto, Masaya Nakamura, Takeo Nagura

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


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.

Original languageEnglish
Article number7200
Pages (from-to)1-10
Number of pages10
JournalSensors (Switzerland)
Issue number24
Publication statusPublished - 2020 Dec 2


  • Ergonomics
  • Intra-tester reliability
  • Muscle hardness
  • Muscle hardness meter
  • Strain ratio
  • Trapezius muscle
  • Ultrasound strain elastography

ASJC Scopus subject areas

  • Analytical Chemistry
  • Information Systems
  • Atomic and Molecular Physics, and Optics
  • Biochemistry
  • Instrumentation
  • Electrical and Electronic Engineering


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