Exercise loading and cortical bone distribution at the tibial shaft
Research Highlights
►Cortical bone is not a uniform tissue, and its density varies. ►It is not yet known, whether the varying vBMD distribution is loading dependent. ►No loading dependency was observed in vBMD distribution between loading groups. ►Cortical bone vBMD distributions are not modulated by exercise loading.
Introduction
The strength of a whole bone is an important predictor of fracture risk, and is determined by the material and architectural properties of bone [1], [2], [3]. It is well known that bones adapt to prevalent imposed loads and muscle forces mostly via changing their mineral mass and architecture, rather than altering the material properties [4], [5]. Currently there are a number of X-ray based bone imaging techniques that permit a reasonable estimation of the apparent volumetric BMD (vBMD) of the cortex, which reflects both the porosity of bone tissue, mineralization and other bone material properties [6], [7], [8]. Further, it has been reported that about 70% of the age-related reduction in cortical vBMD is attributable to increased porosity [6], which suggests that apparent vBMD of the cortex would provide an adequate surrogate of cortical porosity [9].
It is well established that cortical vBMD within long bones is not uniform, and that there are differences between individuals both around the bone cross-section [10], [11], [12], [13], [14], [15], [16] and along its axial length [13], [14], [15]. These differences observed in the distribution of cortical vBMD between different sectors around the center of mass or neutral axis (polar distribution), and within the circumferential layers within the cortex (radial distribution), during growth [10], [11], [17], and aging [12], [13], [16] have raised an important question as to whether loading plays an important role in modulating the distribution of cortical bone density [10], [11]. To date, such changes have been observed in a single randomized controlled trial (RCT) investigating both the polar and radial distribution in response to exercise and hormone replacement therapy in postmenopausal women [18].
In our previous analyses of athletes' bone data, the long-term specific exercise loading was clearly associated with direction-specific structural adaptations at the tibial midshaft [19], [20], [21], [22]. To extend this geometric analysis to apparent material properties of cortical bone, the present study was carried out to evaluate whether cortical vBMD distribution within the cortical envelope (i.e. radial distribution) or in different anatomic directions around the cortex (i.e. polar distribution) is associated with long-term exercise loading, and whether they are related to specific loading patterns in athletes involved in a diverse range of sporting activities.
Section snippets
Methods
A convenience sample of data from 180 premenopausal women representing athletes with a long history of participation in different sports and 41 physically active, non-athletic referents (Table 1) was used in the present study [19], [21], [22], [23]. The age at which the athletes started their competitive career in sports was obtained from a questionnaire. Based on each athlete's sport, they were divided into five near-distinct types of exercise loading as previously reported [19], [21], [23]:
Results
Descriptive characteristics of the study groups are provided in Table 1. There were no amenorrheic women in any group. The proportion of women using hormonal contraceptives varied from 38% to 60% among the different exercise loading groups, and it was 56% among the referents. ANOVA indicated that the proportion of hormonal contraceptives users did not differ between groups (F = 0.512, P = 0.767).
Discussion
Present findings indicate that there was no detectable interaction between the type of exercise loading and the general pattern of radial or polar distribution in cortical vBMD at the tibial mid-shaft. It is, however, noted that we found significantly lower cortical vBMD between some exercise loading groups and referents at specific radial segments and polar sectors. In particular, we found that cortical vBMD in athletes representing high-impact (triple jumpers, high jumpers and hurdlers) and
Acknowledgments
This study was financially supported by Competitive Research Funding of the Pirkanmaa Hospital District, Tampere University Hospital (Grant 9K121), the Finnish Ministry of Education and the Päivikki and Sakari Sohlberg Foundation. Associate Professor Robin Daly is supported by a National Health and Medical Research Council (NHMRC) Career Development Award (ID 425849).
References (36)
- et al.
Understanding bone strength: size isn't everything
Bone
(2001) The many adaptations of bone
J Biomech
(2003)- et al.
Three-dimensional characterization of cortical bone microstructure by microcomputed tomography: validation with ultrasonic and microscopic measurements
J Orthop Sci
(2007) Determinants of the mechanical properties of bones
J Biomech
(1991)- et al.
Regional differences in cortical bone mineral density in the weight-bearing long bone shaft—a pQCT study
Bone
(2005) - et al.
Regional differences in cortical porosity in the fractured femoral neck
Bone
(1999) - et al.
Anatomic variation in the elastic anisotropy of cortical bone tissue in the human femur
J Mech Behav Biomed Mater
(2009) - et al.
Spatial distribution of acoustic and elastic properties of human femoral cortical bone
J Biomech
(2004) - et al.
Change in bone mass distribution induced by hormone replacement therapy and high-impact physical exercise in post-menopausal women
Bone
(2002) - et al.
Loading modalities and bone structures at nonweight-bearing upper extremity and weight-bearing lower extremity: a pQCT study of adult female athletes
Bone
(2006)
Analyzing cortical bone cross-sectional geometry by peripheral QCT: comparison with bone histomorphometry
J Clin Densitom
Bone mass and geometry of the tibia and the radius of master sprinters, middle and long distance runners, race-walkers and sedentary control participants: a pQCT study
Bone
History of amenorrhoea compromises some of the exercise-induced benefits in cortical and trabecular bone in the peripheral and axial skeleton: a study in retired elite gymnasts
Bone
Musculoskeletal design in relation to body size
J Biomech
Bone curvature: sacrificing strength for load predictability?
J Theor Biol
The distribution of material properties in the equine third metacarpal bone serves to enhance sagittal bending
J Biomech
Principles of determination and verification of muscle forces in the human musculoskeletal system: muscle forces to minimise bending stress
J Biomech
Detrimental effect of oral contraceptives on parameters of bone mass and geometry in a cohort of 248 young women
Bone
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