Passive stiffness of monoarticular lower leg muscles is influenced by knee joint angle
While several studies demonstrated the occurrence of intermuscular mechanical interactions, the physiological significance of these interactions remains a matter of debate. The purpose of this study was to quantify the localized changes in the shear modulus of the gastrocnemius lateralis (GL), monoarticular dorsi- and plantar-flexor muscles induced by a change in knee angle.
Participants underwent slow passive ankle rotations at the following two knee positions: knee flexed at 90° and knee fully extended. Ultrasound shear wave elastography was used to assess the muscle shear modulus of the GL, soleus [both proximally (SOL-proximal) and distally (SOL distal)], peroneus longus (PERL), and tibialis anterior (TA). This was performed during two experimental sessions (experiment I: n = 11; experiment II: n = 10). The shear modulus of each muscle was compared between the two knee positions.
The shear modulus was significantly higher when the knee was fully extended than when the knee was flexed (P < 0.001) for the GL (averaged increase on the whole range of motion: + 5.8 ± 1.3 kPa), SOL distal (+ 4.5 ± 1.5 kPa), PERL (+ 1.1 ± 0.7 kPa), and TA (+ 1.6 ± 1.0 kPa). In contrast, a lower SOL-proximal shear modulus (P < 0.001, − 5.9 ± 1.0 kPa) was observed.
As the muscle shear modulus is linearly related to passive muscle force, these results provide evidence of a non-negligible intermuscular mechanical interaction between the human lower leg muscles during passive ankle rotations. The role of these interactions in the production of coordinated movements requires further investigation.
KeywordsUltrasound Shear modulus Shear wave elastography Intermuscular mechanical interactions Epimuscular myofascial force transmission
Analysis of variance
Magnetic resonance imaging
Region of interest
Range of motion
Supersonic shear imaging
This study was supported by grants from the European Regional development Fund (ERDF, no. 37400), the Region Pays de la Loire (QUETE project), and by the Interdisciplinary program from the University of Nantes.
FA, RJA, SRF, CAY, RG, FH, and AN conceived and designed research. FA, RJA, SRF, and LL conducted experiments. FA, RJA and AN analyzed data. FA and RJA wrote the manuscript. All authors read and approved the manuscript.
Compliance with ethical standards
Conflict of interest
The authors have no conflict of interest.
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