Biceps brachii muscle hardness assessed by a push-in meter in comparison to ultrasound strain elastography

Mitsuyoshi Murayama,Kazunori Nosaka,Tsugutake Yoneda,Takayuki Inami,Norihiro Shima

doi:10.1038/s41598-020-77330-5

Mitsuyoshi Murayama, Kazunori Nosaka + Show 3 more

Open Access

https://doi.org/10.1038/s41598-020-77330-5

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Abstract

This study investigated the relationship between push-in meter (PM) and ultrasound strain elastography (USE) for biceps brachii (BB) muscle hardness. BB hardness of 21 young men was assessed by PM and USE during rest and isometric contractions of six different intensities (15, 30, 45, 60, 75, 90% of maximal voluntary contraction: MVC) at 30°, 60° and 90° elbow flexion. Muscle hardness (E) was calculated from the force–displacement relationship in PM, and strain ratio (SR) between an acoustic coupler (elastic modulus: 22.6 kPa) and different regions of interest (ROIs) in BB was calculated and converted to Young’s modulus (YM) in USE. In resting muscle, E was 26.1 ± 6.4 kPa, and SR and YM for the whole BB was 0.88 ± 0.4 and 30.8 ± 12.8 kPa, respectively. A significant (p < 0.01) correlation was evident between E and logarithmical transformed SR (LTSR) for the ROI of whole BB (r = − 0.626), and E and converted YM (r = 0.615). E increased approximately ninefold from resting to 90% MVC, and E and LTSR (r = − 0.732 to − 0.880), and E and converted YM for the SR above 0.1 were correlated (r = 0.599–0.768, p < 0.01). These results suggest that muscle hardness values obtained by PM and USE are comparable.

Highlights

This study investigated the relationship between push-in meter (PM) and ultrasound strain elastography (USE) for biceps brachii (BB) muscle hardness
A dependent t-test showed that the converted Young’s modulus (YM) of the whole BB (30.8 ± 12.8 kPa) was significantly (p = 0.048) greater than the muscle hardness assessed by E (26.1 ± 6.4 kPa), but the two values were significantly correlated (r = 0.615, p = 0.003)
The present study compared biceps brachii muscle hardness value E (Young’s modulus: YM) measured by PM and strain ratio (SR) measured by USE for the resting (Experiment 1) and contracting (Experiment 2) conditions to test the hypothesis that E and SR would be significantly correlated

Summary

Introduction

This study investigated the relationship between push-in meter (PM) and ultrasound strain elastography (USE) for biceps brachii (BB) muscle hardness. E increased approximately ninefold from resting to 90% MVC, and E and LTSR (r = − 0.732 to − 0.880), and E and converted YM for the SR above 0.1 were correlated (r = 0.599–0.768, p < 0.01) These results suggest that muscle hardness values obtained by PM and USE are comparable. It has not been systematically investigated whether muscle hardness assessed by PM and USE is comparable In both PM and USE, the measurement principle in evaluating the relationship between the force and displacement is the same. Three studies compared between a hand-held PM and USE, and reported that the muscle hardness changes before and after exercise or myofascial release therapy assessed by the two methods were similar[14,15,16].

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