Relationship between isometric contraction intensity and muscle hardness assessed by ultrasound strain elastography

Takayuki Inami, Toru Tsujimura, Takuya Shimizu, Takemasa Watanabe, Wing Yin Lau, Kazunori Nosaka

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Introduction: Ultrasound elastography is used to assess muscle hardness or stiffness; however, no previous studies have validated muscle hardness measures using ultrasound strain elastography (SE). This study investigated the relationship between plantar flexor isometric contraction intensity and gastrocnemius hardness assessed by SE. We hypothesised that the muscle would become harder linearly with an increase in the contraction intensity of the plantar flexors. Methods: Fifteen young women (20.1 ± 0.8 years) performed isometric contractions of the ankle plantar flexors at four different intensities (25, 50, 75, 100% of maximal voluntary contraction force: MVC) at 0° plantar flexion. Using SE images, the strain ratio (SR) between the muscle and an acoustic coupler (elastic modulus 22.6 kPa) placed over the skin was calculated (muscle/coupler); pennation angle and muscle thickness were measured for the resting and contracting conditions. Results: SR decreased with increasing contraction intensity from rest (1.28 ± 0.20) to 25% (0.99 ± 0.21), 50% (0.61 ± 0.15), 75% (0.34 ± 0.1) and 100% MVC (0.20 ± 0.05). SR decreased linearly (P < 0.05) with increasing MVC from rest to 75% MVC, but levelled off from 75 and 100% MVC. SR was negatively correlated with pennation angle (r = −0.80, P < 0.01) and muscle thickness (r= −0.78, P< 0.01). Conclusion: SR appears to represent muscle hardness changes in response to contraction intensity changes, in the assumption that the gastrocnemius muscle contraction intensity is proportional to the plantar flexion intensity. We concluded that gastrocnemius muscle hardness changes could be validly assessed by SR, and the force–hardness relationship was not linear.

Original languageEnglish
Pages (from-to)843-852
Number of pages10
JournalEuropean Journal of Applied Physiology
Volume117
Issue number5
DOIs
Publication statusPublished - 2017 May 1
Externally publishedYes

Fingerprint

Elasticity Imaging Techniques
Isometric Contraction
Hardness
Muscles
Skeletal Muscle
Elastic Modulus
Muscle Contraction
Acoustics
Ankle
Skin

Keywords

  • Gastrocnemius
  • Muscle force
  • Muscle thickness
  • Pennation angle
  • Strain ratio

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Public Health, Environmental and Occupational Health
  • Physiology (medical)

Cite this

Relationship between isometric contraction intensity and muscle hardness assessed by ultrasound strain elastography. / Inami, Takayuki; Tsujimura, Toru; Shimizu, Takuya; Watanabe, Takemasa; Lau, Wing Yin; Nosaka, Kazunori.

In: European Journal of Applied Physiology, Vol. 117, No. 5, 01.05.2017, p. 843-852.

Research output: Contribution to journalArticle

Inami, Takayuki ; Tsujimura, Toru ; Shimizu, Takuya ; Watanabe, Takemasa ; Lau, Wing Yin ; Nosaka, Kazunori. / Relationship between isometric contraction intensity and muscle hardness assessed by ultrasound strain elastography. In: European Journal of Applied Physiology. 2017 ; Vol. 117, No. 5. pp. 843-852.
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AU - Lau, Wing Yin

AU - Nosaka, Kazunori

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KW - Muscle force

KW - Muscle thickness

KW - Pennation angle

KW - Strain ratio

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