Vaz João R, Neto Tiago, Correia José Pedro, Infante Jorge, Freitas Sandro R
Neuromuscular Research Lab, Faculty of Human Kinetics, University of Lisbon, 1499-002 Lisbon, Portugal.
CIPER, Faculty of Human Kinetics, 1499-002 Lisbon, Portugal.
J Funct Morphol Kinesiol. 2021 Feb 10;6(1):18. doi: 10.3390/jfmk6010018.
This study sought to investigate whether the stiffness of the biceps femoris long head differs between proximal and distal regions during isometric knee flexion at different contraction intensities and muscle lengths. Twelve healthy individuals performed knee flexion isometric contractions at 20% and 60% of maximum voluntary isometric contraction, with the knee flexed at 15 and 45 degrees. Muscle stiffness assessment was performed using ultrasound-based shear wave elastography. Proximal and distal regions of the biceps femoris long head were assessed. Biceps femoris long head muscle showed a greater stiffness (i) in the distal region, (ii) at higher contraction intensity, and (iii) at longer muscle length. The proximal-to-distal stiffness ratio was significantly lower than 1 (i.e., heterogenous) at lower contraction intensity regardless of the muscle length. However, this was not observed at higher contraction intensity. This study is the first to show heterogeneity in the active stiffness of the biceps femoris long head. Given the greater incidence of injury at the proximal region of biceps femoris long head, this study opens new directions for future research. Additionally, the present study results indicate that studies assessing muscle stiffness at one single muscle region should be interpreted with caution.
本研究旨在探究在不同收缩强度和肌肉长度下进行等长屈膝时，股二头肌长头近端和远端区域的刚度是否存在差异。12名健康个体在最大自主等长收缩的20%和60%强度下进行屈膝等长收缩，膝关节分别屈曲15度和45度。使用基于超声的剪切波弹性成像技术进行肌肉刚度评估。对股二头肌长头的近端和远端区域进行评估。结果显示，股二头肌长头肌肉在（i）远端区域、（ii）较高收缩强度以及（iii）较长肌肉长度时表现出更大的刚度。在较低收缩强度下，无论肌肉长度如何，近端与远端刚度比均显著低于1（即不均匀）。然而，在较高收缩强度下未观察到这种情况。本研究首次表明股二头肌长头主动刚度存在不均匀性。鉴于股二头肌长头近端区域损伤发生率较高，本研究为未来研究开辟了新方向。此外，本研究结果表明，对单个肌肉区域的肌肉刚度评估研究应谨慎解读。
