The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


Are loading patterns reflected in the relationship between musculoskeletal stress markers and biomechanical properties of the humeral diaphysis?

SIRPA T. NIINIMÄKI1 and MARKKU E. NISKANEN2.

1Biology, University of Oulu, 2Archaeology, University of Oulu

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Physical activity should affect both musculoskeletal stress markers (MSM) at entheses and bone diaphyseal strength. Furthermore, the same mechanisms of bone remodeling may be responsible for both the appearance of MSMs and altering of diaphyseal dimensions. Thus, these two types of measurements should covary within individuals. The relationship between MSM and bone biomechanical properties, namely torsional and average bending rigidity (J) of the diaphysis, was studied using three skeletal samples: early 20th century Finnish (Helsinki) and two medieval English (Blackgate and York) populations. Covariance between MSMs and J was studied by scoring three fibrous MSMs (pectoralis major, teres major and deltoid) and measuring J of four cross-sectional locations (80%, 65%, 50% and 35% of humeral length from the distal end). As some of these cross-sectional locations house the attachment for the studied muscles and some do not, location-specific as well as overall covariance between MSMs and J could be studied. Results indicate that although there is some covariance between MSMs and J there is also a considerable amount of variance in MSM that could not be explained by physical activity, age, size, or sample. Covariance between MSMs and J was not location-specific. Furthermore, significant results were found for males only. In this study the causal factors behind the development of MSM were studied secondarily as the covariance between activity-related changes in MSM and J. It seems that although MSMs reflect in part physical activity there are also other factors that have a significant influence on their appearance.

This study was funded by National Science Foundation, grant number 0642297, and Finnish Cultural Foundation.

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