Influence of physical activity on the regulation of bone density

Whalen, Robert T.; Carter, D.R.; Steele, Charles R.

doi:10.1016/0021-9290(88)90015-2

Cited by 250 publications

(110 citation statements)

References 41 publications

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“…Here, the rule has been modified such that the growth density is rate-independent, consistent with the modeling of the remaining growth parameters. Typical values of the exponential material parameter are 2 ≤ k ≤ 7 [54].…”

Section: Constitutive Assumptionsmentioning

confidence: 99%

Material growth in thermoelastic continua: Theory, algorithmics, and simulation

Vignes

Papadopoulos

2010

Computer Methods in Applied Mechanics and Engineering

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To this end, a theoretical formulation of stress-induced volumetric material growth in thermoelastic continua is developed. The theory derives, without the classical continuum mechanics assumption of mass conservation, the balance laws governing the mechanics of solids capable of growth. Also, a proposed extension of classical thermodynamic theory provides a foundation for developing general constitutive relations. The theory is consistent 2 in the sense that classical thermoelastic continuum theory is embedded as a special case.Two growth mechanisms, a kinematic and a constitutive contribution, coupled in the most general case of growth, are identified. This identification allows for the commonly employed special cases of density-preserving growth and volume-preserving growth to be easily recovered. In the theory, material growth is regulated by a three-surface activation criterion and corresponding flow rules. A simple model for rate-independent finite growth is proposed based on this formulation. The associated algorithmic implementation, including a method for solving the underlying differential/algebraic equations for growth, is examined in the context of an implicit finite element method. Selected numerical simulations are presented that showcase the predictive capacity of the model for both soft and hard biomaterials. Professor Panayiotis Papadopoulos, Chair i

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Section: Constitutive Assumptionsmentioning

confidence: 99%

Material growth in thermoelastic continua: Theory, algorithmics, and simulation

Vignes

Papadopoulos

2010

Computer Methods in Applied Mechanics and Engineering

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“…For a standard definition of various types of exercise we used the work of Whalen et al [22] who defined six different activity levels, ranging from sedentary to a1 hletic. These were quantified in terms of the amount of time and number of cycles spent carrying out spe- Table 2 for the specification of the various actions listed in Table 1.…”

Section: Stress Analysis Of the Human Tibiamentioning

confidence: 99%

“…For vere training conditions; Rubin and Lanyon [ 1 71 showed taken from the femur Of a 27-year-01d that the peak value lies between 2100 and 3200 pa for a 1251 failed in 120,000 cycles at a strain range of about wide range of animals, Values for llormal walking are 5700 microstrain (p&). In practice fractures 'Om-smaller by a factor of 2.5-3 [22]. It seeins from these monly Occur after this many months of training) but the maximum strain which occurs during strenuous exercise [3,17] is only in the range to results that stress fractures should never happen, but we know that they do, and furthermore that animals protect themselves against high levels of strain (or high numbers of repetitions), increasing bone mass and area by deposition.…”

Section: Introductionmentioning

confidence: 99%

The prediction of stress fractures using a ‘stressed volume’ concept

Taylor

Kuiper

2001

Journal Orthopaedic Research

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This paper addresses an anomaly which exists in the current literature regarding stress fractures. Analysis of the data on fatigue strength of bone samples in vitro would conclude that these fractures should never occur at the strain levels known to occur in vivo. This anomaly can be resolved by including in the analysis the effect of stressed volume, whereby larger volumes of material are expected to have worse fatigue properties. A Weibull analysis was used to predict the probability of failure, pt; this was an upperbound prediction because it did not include the effects of remodelling and adaptation. Combining this analysis with a finite element model of the human tibia, we predicted a Pf value of 21% after five weeks of strenuous exercise, which is comparable with reported incidences in military personnel. The high incidence of stress fractures in the cannon bone of racehorses could also be predicted (Pr = 62'%, compared to 70% experimentally). The approach can be used to investigate the effect of variables in the exercise regime such as the distance run per day and the use of improved footwear. It can also predict the increased risk of stress fractures in elderly people. The results suggest certain simple rules which may be of clinical value in designing exercise regimes and in understanding the risk factors for this type of injury.

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“…General rules for bone adaptation are relatively well established, i.e. ; bones respond increasingly with increasing 1) strain rate, 2) strain magnitude and 3) number of loading cycles (Lanyon, 1987;Turner, 1998;Whalen et al, 1988). In addition, loading direction affects the response, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, indirect estimates have to be used in practical applications. Since, intuitively there is an association between ground reaction force and bone strains, it has been suggested that osteogenic index may be calculated from reaction forces (Turner & Robling, 2003;Whalen et al, 1988). Subsequently, reaction force based osteogenic index has been shown to be able to successfully differentiate two exercise regimes producing differing bone responses from each other in a prospective human study (von Stengel et al, 2007;.…”

Section: Introductionmentioning

confidence: 99%