The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Activity type and level influence growth rate, remodeling, and diaphyseal geometry of cortical bone


1Evolutionary Anthropology, Duke University, 2Department of Anthropology, University of Toronto, 3Department of Anatomy, Midwestern University, 4Center for the Advanced Study of Hominid Paleobiology, Department of Anthropology, The George Washington University, 5Human Origins Program, National Museum of Natural History, Smithsonian Institution, Washington DC

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Cortical bone shape and microstructure are often used to reconstruct behavioral activities and life histories of individuals in the archaeological and fossil records, but much remains unknown about how exercise levels and the nature of activity influence cortical bone. Here, we used a mouse model to study the effects of activity on mechanical and microstructural properties of cortical bone development. Female wild-type mice (n=30) were subjected to three experimental activity patterns: sedentary controls, activity-wheel running, and activity-vertical climbing. During the experiment, each mouse was given three subcutaneous injections with fluorescent bone-labeling dyes at known intervals to allow for histological examination of bone growth rates and remodeling. After the experiment, two 100-micron thick cross-sections of the humerus were prepared for microscopic and cross-sectional geometric analysis. The wheel-running mice, who exercised the most, had a significantly faster bone growth and showed higher proportions of fast forming tissue. Compared to them, the vertical-climbing mice, who climbed meshed cages an average of 140m each night, had a much slower bone growth but showed more histologic variation in bone remodeling, such as an increase in numbers of osteon and drifting-osteon. However, the differences in diaphyseal geometry between the activity groups were less pronounced than the differences in microstructure. The results of this study suggest that coritcal anatomy is more sensitive than gross geometry to variations in the degree and type of activity, and may allow researchers to make refined inferences about activity and locomotor history from skeletal remains.

This study was funded by Wenner-Gren Foundation Dissertation Fieldwork Grants to KR and DG, NSF Doctoral Dissertation Improvement Grant BCS-0824552, NSF DGE-0801634, and GW Academic Excellence funding to the Center for the Advanced Study of Hominid Paleobiology.

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