Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; Department of Industrial Engineering, University of Trento, Trento, Italy.
Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; Department of Industrial Engineering, University of Trento, Trento, Italy.
J Biomech. 2021 Jan 4;114:110110. doi: 10.1016/j.jbiomech.2020.110110. Epub 2020 Nov 30.
We combined ultrafast-ultrasound with dynamometric measurements to assess the associations between muscle structural properties and the rate of torque development (RTD) during isometric explosive fixed-end plantar flexor contractions. The torque-time signal was recorded for the plantaflexor muscles in fifteen men and the peak value of RTD was obtained. Tendon stiffness (kT) and muscle stiffness (kM) of the Gastrocnemius Medialis (GM) were assessed during maximal isometric voluntary contractions (MVC) and quick release using ultrafast ultrasound (1000 Hz). During the explosive contraction, the GM geometrical changes were recorded and the belly gearing (belly velocity/fascicle velocity) was calculated. Pearson's correlation coefficient was used to assess the correlation between variables, whereas equality of correlation coefficients between RTD and kT and kM was tested by means of the Hotelling's statistics. During explosive contraction, kT was higher than kM (~55 and ~30 N⋅mm1, respectively). RTD positively correlated with kM (r = 0.75, p < 0.001), kT (r = 0.58, p = 0.044) and belly gearing (r = 0.78, p < 0.001). However, Hotelling's test showed no significant differences between the correlation coefficients between RTD and muscle and tendon stiffness. Further, belly gearing was significantly positively correlated with kM only (r = 0.79, p < 0.001). Our data suggest that muscle and tendon stiffness are similarly associated with RTD. Given the association with belly gearing, muscle stiffness seems to play an important role in determining the muscle length changes, thereby affecting the muscle force transmission capacity during the transient phases.
我们结合超快速超声和测力测量来评估肌肉结构特性与等速向心足底屈肌收缩期间的扭矩发展速率 (RTD) 之间的关系。记录十五名男性的足底屈肌的扭矩-时间信号，并获得 RTD 的峰值。在最大等长自主收缩 (MVC) 和快速释放期间使用超快速超声 (1000 Hz) 评估比目鱼肌的肌腱刚度 (kT) 和肌肉刚度 (kM)。在爆发性收缩期间，记录 GM 的几何变化，并计算腹部传动比 (腹部速度/肌束速度)。使用 Pearson 相关系数评估变量之间的相关性，而通过 Hotelling 统计检验来测试 RTD 与 kT 和 kM 之间的相关系数是否相等。在爆发性收缩期间，kT 高于 kM（分别约为 55 和 30 N⋅mm1）。RTD 与 kM（r=0.75，p<0.001）、kT（r=0.58，p=0.044）和腹部传动比（r=0.78，p<0.001）呈正相关。然而，Hotelling 检验表明 RTD 与肌肉和肌腱刚度之间的相关系数没有显著差异。此外，腹部传动比仅与 kM 呈显著正相关（r=0.79，p<0.001）。我们的数据表明，肌肉和肌腱刚度与 RTD 具有相似的相关性。鉴于与腹部传动比的关系，肌肉刚度似乎在确定肌肉长度变化方面起着重要作用，从而影响瞬态阶段的肌肉力量传递能力。
