Physical Training Outcome Predictions With Biomechanics, Part II: Overuse Injury Modeling.

Objectives: In Part II of a two-part series, we develop a phenomenological model of a negative outcome of U.S. Army Basic Combat Training that affects a large proportion of trainees.

Physical Training Outcome Predictions With Biomechanics, Part I: Army Physical Fitness Test Modeling.

Objectives: The U.S. Army Basic Combat Training (BCT) is the first step in preparing soldier trainees for the physical demands of the military.

Increased density and periosteal expansion of the tibia in young adult men following short-term arduous training.

Purpose: Few human studies have reported early structural adaptations of bone to weight-bearing exercise, which provide a greater contribution to improved bone strength than increased density. This prospective study examined site- and regional-specific adaptations of the tibia during arduous training in a cohort of male military (infantry) recruits to better understand how bone responds in vivo to mechanical loading.

Methods: Tibial bone density and geometry were measured in 90 British Army male recruits (ages 21±3years, height: 1.

Odd-impact loading results in increased cortical area and moments of inertia in collegiate athletes.

Purpose: The purpose of this study was to investigate tibial changes in volumetric bone mineral density and geometry that take place in athletes from pre- to post-season.

Methods: Female college athletes (n = 36) and ten controls recruited from the student population were included in the study. Participants had their left tibia scanned by pQCT at 4, 20, and 66 % of the overall length from the distal end before and after their competitive seasons.

Variation in tibial functionality and fracture susceptibility among healthy, young adults arises from the acquisition of biologically distinct sets of traits.

Physiological systems like bone respond to many genetic and environmental factors by adjusting traits in a highly coordinated, compensatory manner to establish organ-level function. To be mechanically functional, a bone should be sufficiently stiff and strong to support physiological loads. Factors impairing this process are expected to compromise strength and increase fracture risk.

Biological constraints that limit compensation of a common skeletal trait variant lead to inequivalence of tibial function among healthy young adults.

Having a better understanding of how complex systems like bone compensate for the natural variation in bone width to establish mechanical function will benefit efforts to identify traits contributing to fracture risk. Using a collection of pQCT images of the tibial diaphysis from 696 young adult women and men, we tested the hypothesis that bone cells cannot surmount the nonlinear relationship between bone width and whole bone stiffness to establish functional equivalence across a healthy population. Intrinsic cellular constraints limited the degree of compensation, leading to functional inequivalence relative to robustness, with slender tibias being as much as two to three times less stiff relative to body size compared with robust tibias.

Sex differences in parameters of bone strength in new recruits: beyond bone density.

Background: Stress fracture (SF) injuries in new recruits have long been attributed to low bone mineral density (BMD). Low areal BMD assessed using two-dimensional dual-energy x-ray absorptiometry imaging, however, reflects structural density and is affected by smaller measures of bone geometry. Recent studies support a relationship between bone size and SF and indicate that slender bones are more susceptible to damage under identical loading conditions.

A computational evaluation of the effect of intramedullary nail material properties on the stabilization of simulated femoral shaft fractures.

Titanium flexible intramedullary nails have become far more prevalent for stabilization of pediatric femur fractures in recent years. While steel may be expected to have superior fracture stability due to its higher elastic modulus; titanium alloy has experimentally demonstrated improved biomechanical stability, as measured by gap closure and nail slippage. The purpose of this study was to verify these observations computationally, and thus, explain why titanium alloy may be better suited for surgical fixation of fractured femurs.

Continuum remodeling revisited : deformation rate driven functional adaptation using a hypoelastic constitutive law.

Recent research effort in bone remodeling has been directed toward describing interstitial fluid flow in the lacuno-canalicular system and its potential as a cellular stimulus. Regardless of the precise contents of the mechanotransduction "black box", it seems clear that the fluid flow on which the remodeling is predicated cannot occur under static loading conditions. In an attempt to help continuum remodeling simulations catch up with cellular and subcellular research, this paper presents a simple, strain rate driven remodeling algorithm for density allocation and principal material direction rotations.