It is widely assumed that mechanical loads underwent by bones during life are related to muscular development, but there is a lack of quantifiable evidences in this sense. The purpose of this study is to explain how humeral diaphyseal shape is modified by muscular development. Moreover, we aim to determine what upper-limb muscles are more relevant on humeral rigidity increase and how this rigidity is related to diaphyseal shape. The development grade of 16 upper-limb musculoskeletal markers was studied on the humeri, ulnas and radius of 30 male individuals between 30 and 45 years old from Eastern Spain archaeological sites. Three-dimensional images of the humeri were taken to digitalize the external contours of cross-sections at 35% of bone length from its distal end. Medullary canal contours were estimated from humeral biplanar radiographs. Humeral cross-sections were imported into ImageJ and analyzed using Moment Macro, and cross-sectional properties were calculated. External contours shape was inferred from a number of landmarks and semilandmarks and studied using geometric morphometrics methods. Results based on partial least squares regressions show that humeral rigidity increase occurs when external cross-section contour at 35% of bone length tends to a circular shape. Moreover, the development of biceps brachii is the one with the greatest relevance on humeral rigidity increase, especially on compression and tension rigidities, whereas diaphyseal contour shape at 35% of bone length is mainly affected by brachialis anticus development. This study was partially funded by CGL2008-00800/BOS, FPU grant AP2009-5102 and Juan de la Cierva grant JCI-2010-08157.
|Number of pages||172|
|Journal||American Journal of Physical Anthropology|
|Publication status||Published - 2012|