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Signal transduction and exercise
Published in Adam P. Sharples, James P. Morton, Henning Wackerhage, Molecular Exercise Physiology, 2022
Brendan Egan, Adam P. Sharples
Physiological, or phenotypical, adaptations are changes that occur within individuals in response to external factors such as exercise training, and other environmental factors, such as altitude. For example, a larger muscle mass can be a phenotype caused by performing progressive resistance exercise training, or improved oxygen-carrying capacity through increased haemoglobin mass can be a phenotype after performing aerobic exercise training at altitude. In the history of adaptation research, one early idea is the overload concept proposed by Julius Wolff, who linked the mechanical loading of bones to their adaptation in an 1892 book entitled ‘Das Gesetz der Transformation der Knochen’ [The Law of Bone Remodelling; translated by Maquet and Furlong (1986) (4)]. The original hypothesis is now known as Wolff’s law. This principle can be applied to other organs such as skeletal muscle, if the meaning of the term overload is extended beyond mechanical overload to include the many perturbations to homeostasis that occur with the onset of, and recovery from, exercise. The principle of overload in the context of sport and exercise is indeed one of the core principles of exercise training. Overload in this case refers to an exercise stimulus that perturbs the stability of the internal environment (i.e. homeostasis), and with repeated exercise stimuli produces physiological adaptations, which we call ‘training effects’.
Collagens of the Disc
Published in Peter Ghosh, The Biology of the Intervertebral Disc, 2019
A smaller number of similar analyses were made on the collagen type distribution in discs removed from patients with idopathic scoliosis.108 In individual discs from the apex of the scoliotic curve, the ratio of type I to type II collagens in the annulus fibrosus was different on the convex side compared with the concave side. Type I collagen was enriched in the compressed, concave side of the annulus. An altered distribution in the overall quantity of collagen in scoliotic discs had previously been noted.108 The results on normal and scoliotic discs were taken as evidence that disc tissue can respond metabolically to changing mechanical forces and so alter the local composition of the extracellular matrix to better suit the new loading patterns. Thus, the increased type I collagen content of the posterior wall of the annulus fibrosus during skeletal growth and maturation and the increased type I collagen content in the compressed lateral half of a scoliotic disc were presumably the effects of metabolic responses of the tissue to altered mechanical forces. Such remodeling of a soft connective tissue in response to altered mechanical loading was likened to an expression of Wolff’s Law, originally formulated for the remodeling ability of bone.107 Potential variations in disc composition due to loading history during growth and adolescence may, therefore, be a factor in determining which discs and individuals are predisposed to disc degeneration in adult life.
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Published in Anton Sebastian, A Dictionary of the History of Medicine, 2018
Wolff, Julius (1836–1902) German orthopedic surgeon in Berlin who proposed the Wolff law in 1892 which states that all changes in the functions of the bones are accompanied by definite alteration in their internal structure.
Finite element study on the influence of pore size and structure on stress shielding effect of additive manufactured spinal cage
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Vijay Kumar Meena, Parveen Kalra, Ravindra Kumar Sinha
Spinal injuries and spinal disorders are becoming increasingly common ailments in modern life. One of the most common diseases/ailments is Degenerative Disc Disease, popularly known as DDD (Pannell et al. 2015). The cure involves surgical procedures of degenerated disc and insertion of appropriate implants, namely spinal cages between the vertebrae. Titanium alloy (Ti6Al4V) is the preferred choice for spinal cages due to its high tensile strength, good biocompatibility, good fatigue strength, and corrosion resistance (Ramakrishna et al. 2001). These spinal cages are generally made of solid dense metals/polymers e.g. titanium, Carbon Fiber Reinforced PEEK, etc. Young’s modulus of these materials is much higher than human bone Young’s modulus. The elastic modulus of bone varies between 1 and 20 GPa whereas the elastic modulus of titanium is 110 GPa. Due to this vast difference in elastic modulus, the loads are not transferred from the implant to adjacent bone tissue, resulting in stress shielding between the host bone and the implant. This leads to adaptive resorption of bone tissue and a decrease in mechanical rigidity of the bone as per Wolff’s law (Chen et al. 2010). Similarly, with reduced stress shielding, bone tissues are known to generate deposition of new bone, which increases mechanical rigidity (Stock 2018). Also, the smooth and shiny surface of solid metal implants makes it difficult to integrate with the host bone. This causes amyotrophy and osteonecrosis of bones around the implants, loosening of the implant, distortion of bones, etc (Haibo et al. 2012).
Footedness related differences in femoral bone mineral density in elderly women with osteoporosis
Published in International Journal of Neuroscience, 2020
Nikolaos Tsorlakis, George Grouios, Haralambos Tsorbatzoudis, Vassilia Hatzitaki
The above phenomenon of bone adaptation to imposed mechanical loadings is often referred to the term ‘Wolff’s law’ [28,29], which is essentially the observation that bone changes its external shape and internal architecture in response to applied stresses acting on it [30]. Wolff’s law marked a step forward in the understanding of bone. During 1960s, accumulated evidence supplemented an older paradigm and strongly supported the features of a new one, the ‘Utah Paradigm’, which incited reassessment of some former ideas about skeletal physiology and disease, and still evolves defining a new field of vital biomechanics [31–33]. According to the Utah Paradigm, the frequent and repeated use of muscles with better innervation cause larger loads and greater physical bone strain, increasing the processes of bone resorption and formation through modeling and remodeling [34]. Additionally, a prominent point of this model is that the largest loads on bone come not from static loads, like gravitational forces (i.e. body weight), but rather from repetitive dynamic loads (i.e. contractions of regional muscles). Ergo, muscle strength strongly influences the strength of the load bearing bones which are not limited to weight-bearing ones.
A three-dimensional topology optimization model for tooth-root morphology
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2018
K.-F. Seitz, J. Grabe, T. Köhne
The presented optimization seeks for a topology with minimum compliance, which can be expressed as the system’s strain energy and implicitly minimizes the deformations. This method has been presented in Bendsøe and Sigmund (2003) and Sigmund (2001) by providing a 99 line matlab code. The minimum compliance is chosen in order to achieve a structurally optimized design while considering the stiffness of the structure. Assuming Wolff’s law (1892), the stiffness of the structure has an impact on the bone adaptation and is therefore analyzed in the context of this paper. The structure’s strain energy c can also be defined as a sum over all integration points g of the FE-model (Pucker and Grabe 2011; Seitz and Grabe 2016). The optimization problem is therefore proposed as in equation (3), which is subjected to a volume constraint and the constrained domain for the relative material density ρe.