TY  - JOUR
A1  - Herssens, Nolan
A1  - Cowburn, James
A1  - Albracht, Kirsten
A1  - Braunstein, Bjoern
A1  - Cazzola, Dario
A1  - Colyer, Steffi
A1  - Minetti, Alberto E.
A1  - Pavei, Gaspare
A1  - Rittweger, Jörn
A1  - Weber, Tobias
A1  - Green, David A.
ED  - Cattaneo, Luigi
T1  - Movement in low gravity environments (MoLo) programme – the MoLo-L.O.O.P. study protocol
JF  - PLOS ONE / Public Library of Science
N2  - Exposure to prolonged periods in microgravity is associated with deconditioning of the musculoskeletal system due to chronic changes in mechanical stimulation. Given astronauts will operate on the Lunar surface for extended periods of time, it is critical to quantify both external (e.g., ground reaction forces) and internal (e.g., joint reaction forces) loads of relevant movements performed during Lunar missions. Such knowledge is key to predict musculoskeletal deconditioning and determine appropriate exercise countermeasures associated with extended exposure to hypogravity.
Y1  - 2022
U6  - https://doi.org/10.1371/journal.pone.0278051
SN  - 1932-6203
VL  - 17
IS  - 11
PB  - Plos
CY  - San Francisco
ER  - 
TY  - JOUR
A1  - Bhattarai, Aroj
A1  - Horbach, Andreas
A1  - Staat, Manfred
A1  - Kowalczyk, Wojciech
A1  - Tran, Thanh Ngoc
T1  - Virgin passive colon biomechanics and a literature review of active contraction constitutive models
JF  - Biomechanics
N2  - The objective of this paper is to present our findings on the biomechanical aspects of the virgin passive anisotropic hyperelasticity of the porcine colon based on equibiaxial tensile experiments. Firstly, the characterization of the intestine tissues is discussed for a nearly incompressible hyperelastic fiber-reinforced Holzapfel–Gasser–Ogden constitutive model in virgin passive loading conditions. The stability of the evaluated material parameters is checked for the polyconvexity of the adopted strain energy function using positive eigenvalue constraints of the Hessian matrix with MATLAB. The constitutive material description of the intestine with two collagen fibers in the submucosal and muscular layer each has been implemented in the FORTRAN platform of the commercial finite element software LS-DYNA, and two equibiaxial tensile simulations are presented to validate the results with the optical strain images obtained from the experiments. Furthermore, this paper also reviews the existing models of the active smooth muscle cells, but these models have not been computationally studied here. The review part shows that the constitutive models originally developed for the active contraction of skeletal muscle based on Hill’s three-element model, Murphy’s four-state cross-bridge chemical kinetic model and Huxley’s sliding-filament hypothesis, which are mainly used for arteries, are appropriate for numerical contraction numerical analysis of the large intestine.
KW  - virgin passive
KW  - strain energy function
KW  - smooth muscle contraction
KW  - viscoelasticity
KW  - damage
Y1  - 2022
U6  - https://doi.org/10.3390/biomechanics2020013
SN  - 2673-7078
VL  - 2
IS  - 2
SP  - 138
EP  - 157
PB  - MDPI
CY  - Basel
ER  -