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Prevention of Osteoporosis in Children and Adolescents
Published in James M. Rippe, Lifestyle Medicine, 2019
Physical activity is one of the most important lifestyle factors for maximizing bone accrual, bone density, and bone strength in children and adolescents. Abundant evidence from intervention trials and observational studies demonstrates that higher levels of physical activity are associated with greater bone mass, density, and cross-sectional dimensions (e.g. cortical diameter and thickness). Importantly, physical activity levels seen within the range typically observed among healthy children and adolescents are positively associated with bone mass and density.32 Physical activity results in local loads (strains) on bone that affect bone modeling and remodeling. Bone loading that produces unusual strains (greater in magnitude or frequency than typical) will result in increases in bone mass, density, dimensions, or alter the mass distribution. After these adaptations, the strain environment returns to a steady state, and further alterations in loading are needed to elicit further gains in bone strength. Unloading bone, such as with stopping sport participation or musculoskeletal or neurologic injury, results in loss of bone mass and density. This concept of bone regulation is known as the “mechanostat theory.”15
Metabolic and endocrine bone disorders
Published in Ashley W. Blom, David Warwick, Michael R. Whitehouse, Apley and Solomon’s System of Orthopaedics and Trauma, 2017
One of the primary roles of the skeleton is to provide an endoskeleton, transmitting forces applied by muscles acting as external levers for the purposes of locomotion and other activities. The skeleton is designed to withstand different types of forces such as compression, tension, shear and torsion. However, at any one site a specific type of force tends to predominate; for example, compression is the predominant force acting on lumbar vertebrae while tensile forces predominate at the superior surface of the femoral neck. The direction and thickness of trabeculae in cancellous bone are related to regional stress trajectories. This is recognized in Wolff’s law (1896), which states that the architecture and mass of the skeleton are adjusted to withstand the prevailing forces imposed by functional need or deformity (see Figure 7.10). This has led to the concept of the mechanostat, whereby bone remodelling and bone mass are regulated to ensure that bone strain (defined as deformation in response to an externally applied load per unit length) is kept within a target range (Frost, 1987).
Changes in Body Composition with Exercise in Overweight and Obese Children
Published in Henry C. Lukaski, Body Composition, 2017
Scott Going, Joshua Farr, Jennifer Bea
In response to mechanical loading, bones adapt their mass, geometry, and material properties in order to keep typical strains within a safe physiological range and resist fractures. This basic concept has been known for many years (Wolff 1892). The mechanism controlling this feedback regulation, referred to as the “mechanostat” (Frost 1987), has been shown to be carried out at the cellular level by bone remodeling units (BMUs) comprised of osteoclasts that resorb bone and osteoblasts that lay down new bone. The activities of BMUs are coordinated by osteocytes, cells embedded in bone, which have the ability to respond to changes in mechanical loads and tailor the bone remodeling response by increasing the activity and/or number of osteoblasts relative to that of osteoclasts, resulting in net bone gain or loss.
Sex differences in bone mineral content and bone geometry accrual: a review of the Paediatric Bone Mineral Accural Study (1991–2017)
Published in Annals of Human Biology, 2021
Adam D. G. Baxter-Jones, Stefan A. Jackowski
Mechanical loads imposed on bones are directly mediated by muscle force. The largest physiologic loads placed on bones are from muscle contractions, and these are greater than the forces associated with gravity (Janz et al. 2007). This mechanism, described by the mechanostat theory, is particularly evident during periods of skeletal growth. The mechanostat theory postulates that increasing maximal muscle force during growth, or in response to increased loading, will affect bone mass, size, and strength (Frost and Schoenau 2000). These PBMAS results are also in accord with the mechanostat theory that postulates that developmental changes in bone strength are secondary to the increasing loads imposed by larger muscle forces. Hence, the PBMAS results indicate that muscle strength (surrogated by a measure of LM) precedes the increase in bone strength (surrogated by BMC). In girls, total body LM accrual preceded the peak BMC accretion by 0.51 years compared to 0.36 years in boys. These results are compatible with the view that bone development is driven by muscle development (Rauch et al. 2004). Although, the data do not exclude the hypothesis that LM and BMC accrual are independently determined by genetic mechanisms.
An enriched continuum mechanics description of bone tissue to describe mineralization and mechanobiology in bone remodeling
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
M. Martin, P. Pivonka, G. Haïat, V. Sansalone, T. Lemaire
In the past decades, numerous studies have attempted to address the various phenomena that take place simultaneously during bone remodeling. These works are based on Frost’s “mechanostat theory” (Frost 1987) and postulate the existence of a feedback mechanism between mechanical loading and the biochemical activity of bone cells in bone remodeling. Hence, in the wake of this seminal work, multiple phenomenological laws of varying complexity have been developed to describe the evolution of bone porosity (Beaupré et al. 1990; Huiskes et al. 2000), tissue orientation (Huiskes et al. 2000; Doblaré and García 2001), biological and chemical levels (Komarova et al. 2003; Pivonka et al. 2008; Klika et al. 2014) and mineralization (Hernandez et al. 2000; García-Aznar et al. 2005; Rouhi et al. 2007; Ganghoffer et al. 2016).
Modifications in the spectrum of bone mass predictive factors with menopausal status
Published in Endocrine Research, 2018
Stefana Catalina Bilha, Dumitru Branisteanu, Catalin Buzduga, Daniela Constantinescu, Petru Cianga, Ecaterina Anisie, Cristina Gavrilovici, Adrian Covic, Maria Christina Ungureanu
In contrast, LM is an independent predictor of bone mass in women, as proven by the meta-analysis of Ho-Pham et al.5 that included 44 clinical studies published between 1989 and 2013. Lean (muscle) mass and physical activity promote an increase in bone cortical surface and thickness (the mechanostat theory), thus determining the augmentation of both bone mass and bone strength.19 In our study, the relationship between LM and BMD was stronger in premenopausal women, while in postmenopausal females the influence of fat distribution became similarly important even in the absence of age-adjusted analysis. We showed further that age greatly impacts the BMD in postmenopausal women, seemingly by countermanding the effect of lean tissue. Nonetheless, similar to Ho-Pham et al.,5 we found the strongest associations between LM and hip and also the whole-body BMD, respectively, in premenopausal women.