Related Experiment Video
Updated: Jun 21, 2026
16:46
A Novel Stretching Platform for Applications in Cell and Tissue Mechanobiology
Published on: June 3, 2014
Biaxial strain and variable stiffness in aponeuroses
Emanuel Azizi1, Thomas J Roberts
1Brown University, Department of Ecology and Evolutionary Biology, Box G-B204, Providence, RI 02912, USA. manny_azizi@brown.edu
The Journal of Physiology
|July 15, 2009
Summary
Muscle aponeuroses exhibit unique biaxial strain patterns during active contraction, unlike passive stretching. This complex strain behavior is crucial for modulating stiffness and elastic energy storage in muscles.
Area of Science:
- Biomechanics
- Muscle Physiology
- Tendon Research
Background:
- Muscles utilize both free tendons and sheet-like aponeuroses for force transmission.
- Aponeuroses surround muscle bellies, requiring expansion in multiple directions during contraction.
- Understanding aponeurosis mechanics is key to comprehending muscle function and injury.
Purpose of the Study:
- To investigate the strain patterns of the turkey lateral gastrocnemius aponeurosis.
- To compare aponeurosis behavior during active versus passive force production.
- To determine the role of biaxial strain in aponeurosis stiffness modulation.
Main Methods:
- Utilized biplanar high-speed fluoroscopy for in situ tracking of turkey gastrocnemius aponeurosis.
- Measured strain patterns during both active and passive force generation.
- Analyzed longitudinal and transverse strain components and their relationship to stiffness.
Main Results:
- Passive force production induced uniaxial strain, with stretching only in the longitudinal direction.
- Active force production resulted in significant biaxial strain (longitudinal and transverse).
- Transverse strains were approximately four times greater than longitudinal strains during active contraction.
- Longitudinal stiffness varied proportionally with transverse strain, indicating biaxial loading effects.
Conclusions:
- Biaxial strain during active muscle contraction is a distinguishing feature of aponeuroses compared to free tendons.
- This biaxial loading dynamically modulates aponeurosis stiffness along the muscle's line of action.
- Considering only longitudinal strain may underestimate aponeurosis stiffness and elastic energy storage capacity.
Related Concept Videos
01:15Relation between Poisson's ratio, Modulus of Elasticity and Modulus of Rigidity
Deformation occurs in axial and transverse directions when an axial load is applied to a slender bar. This deformation impacts the cubic element within the bar, transforming it into either a rectangular parallelepiped or a rhombus, contingent on its orientation. This transformation process induces shearing strain. Axial loading elicits both shearing and normal strains. Applying an axial load instigates equal normal and shearing stresses on elements oriented at a 45° angle to the load axis.
01:20Normal Strain under Axial Loading
Normal strain under axial loading is an important concept in the field of mechanics of materials. Axial loading implies the application of a force along the axis of a material, like a column or bar. This force can either compress or stretch the material. In the context of axial loading, normal strain is the deformation experienced by the material in the direction of the loading force. It's calculated as the change in length divided by the original length of the material. This unitless ratio...
01:12Transformation of Plane Strain
When analyzing elongated structures like bars subjected to uniformly distributed loads, it is essential to understand the transformation of plane strain when coordinate axes are rotated. This transformation helps to assess how material deformation characteristics vary with orientation, which is crucial in materials science and structural engineering.
Under plane strain conditions, typical for members where one dimension significantly exceeds the others, deformations and resultant strains are...
Under plane strain conditions, typical for members where one dimension significantly exceeds the others, deformations and resultant strains are...
01:22Generalized Hooke's Law
The generalized Hooke's Law is a broadened version of Hooke's Law, which extends to all types of stress and in every direction. Consider an isotropic material shaped into a cube subjected to multiaxial loading. In this scenario, normal stresses are exerted along the three coordinate axes. As a result of these stresses, the cubic shape deforms into a rectangular parallelepiped. Despite this deformation, the new shape maintains equal sides, and there is a normal strain in the direction of the...
01:16Eccentric Axial Loading in a Plane of Symmetry
Eccentric axial loading occurs when an axial load is applied away from the centroidal axis of a structural member. This scenario is common in engineering, where structural elements may not be directly aligned due to various design or functional requirements.
01:29Three-Dimensional Analysis of Strain
Three-dimensional strain analysis is crucial for understanding how materials deform under stress, particularly in elastic, homogeneous materials. This method employs principal stress axes to simplify complex stress states into more understandable forms. Subjected to stress, a small cubic element within a material either expands or contracts along these axes, transforming into a rectangular parallelepiped. This transformation effectively illustrates the material's deformation. The principal...