Relationship between isometric contraction intensity and muscle hardness assessed by ultrasound strain elastography
Relationship between isometric contraction intensity and muscle hardness assessed by ultrasound strain elastography
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DOI：
10.1007/s00421-016-3528-2
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发表时间：
2017-05-01
影响因子：
3
通讯作者：
Nosaka, Kazunori
中科院分区：
文献类型：
--
作者：
Inami, Takayuki;Tsujimura, Toru;Nosaka, Kazunori
超声弹性成像用于评估肌肉硬度或刚度;然而，以前没有研究使用超声应变弹性成像（SE）验证肌肉硬度测量。本研究旨在探讨足底屈肌等长收缩强度与腓肠肌硬度的关系。我们假设，肌肉会变得更硬的线性增加的收缩强度的跖flexors.Methods 15个年轻女性（20.1 +/- 0.8年）进行等长收缩的踝跖屈肌在四个不同的强度（25，50，75，100%的最大自愿收缩力：MVC）在0度跖屈。使用SE图像，肌肉和声耦合器之间的应变比（SR）（弹性模量22.6kPa），（肌肉/耦合器）;结果SR随静息状态下收缩强度的增加而减小（1.28 +/- 0.20）至25%（0.99 +/- 0.21）、50%（0.61 +/- 0.15）、75%（0.34 +/- 0.1）和100% MVC（0.20 +/- 0.05）。SR随MVC的增加而线性下降（P < 0.05），但从75和100%MVC开始趋于平稳。SR与羽状角（r =-0.80，P < 0.01）和肌厚（r =-0.78，P < 0.01）呈负相关。结论SR反映了腓肠肌收缩强度与跖屈强度成正比的肌肉硬度变化。结果表明，应变率能有效地反映腓肠肌的硬度变化，且力-硬度关系不是线性的。
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 degrees 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.