Browsing by Author "Scott M. Fitzpatrick, Committee Member"

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    The Relationship between Body Mass Index and Long Bone Morphology: A Multidirectional Analysis
    (2009-04-20) Agostini, Gina Marie; Ann H. Ross, Committee Chair; D. Troy Case, Committee Member; Scott M. Fitzpatrick, Committee Member
    Obesity has increased significantly during the last three decades in all ages and both sexes among European and African Americans, and Hispanic individuals of Mexican origin. Biomechanical literature is replete with evidence of compensatory adaptations made by overweight individuals to cope with adiposity in daily life, yet aside from correlations between weight and arthritis frequencies, little attention has been paid to the effect that obesity has on the human skeleton. Because a key goal of physical anthropology is to create a thorough and accurate biological profile of individuals being analyzed, more research is needed to investigate implications of obesity, a condition which clearly affected how an individual appeared in life. The goal of this project was two fold: [1] to assess diaphyseal cross-sectional geometry of both humerii, the left femur and the left tibia and [2] to test whether the expression of musculoskeletal stress markers (MSMs) of each bone were affected by weight. Both properties have been shown to be influenced by load and mechanical action resulting from stress-induced remodeling responses at the cellular level. A sample of modern males of European ancestry was utilized for this research. After controlling for age, multivariate statistics show significant (p-value < 0.05) elongation of the mediolateral dimension of the proximal and midshaft femur in overweight individuals. T-tests show that overweight individuals have significantly large ML dimensions in this region (p-value < 0.05), suggesting that femora of overweight individuals undergo abnormally high rates of sagittal stress. These findings correlate well with biomechanical gait analyses, which show that overweight individuals display significant increases in step width and hip abduction, disproportionately large mediolateral ground reaction forces, and longer periods of stance during the walking cycle when compared to normal weight controls. All of these activities, especially when coupled with movement of excess mass, could explain abnormal sagittal stress of the proximal femur. A significant bilateral effect of BMI on the ML dimension of the proximal humeru was also found (p-value < 0.01) after controlling for age. T-tests confirmed that overweight individuals have significantly large dimension in this region (p-value < 0.05), perhaps due to high loads transmitted through the shoulder when an individual uses his arms to rise from a seated position. Despite their success in archaeological assessments of activity, MSMs were not found to be a suitable method of differentiating overweight individuals from normal or underweight individuals. This could be due to biological defense mechanisms at sites of muscle attachment for coping with high routine stresses, genetic influences on MSM expression, presence of both overweight and heavily-muscled individuals in the overweight category, or lack of significant activity differences between overweight and normal or underweight individuals.
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    Sexual Dimorphism in the Tarsals: Implications for Sex Determination.
    (2009-05-01) Harris, Sheena Marie; Scott M. Fitzpatrick, Committee Member; Ann H. Ross, Committee Member; D. Troy Case, Committee Chair
    The accurate determination of sex is the first analytic task of physical anthropologists in the study of human skeletal remains. Correct sex determinations are essential because most other skeletal analyses rely on this to be accurately determined. Although morphological features of the skull and pelvis have been traditionally used for sex determination, certain metric analyses have also been useful. In the absence of the most commonly used bones, metric measurements obtained from the tarsals have the ability to provide accurate information regarding sex. Metric sex assessments are based on the levels of sexual dimorphism between males and females. This thesis evaluates the presence of sexual dimorphism in the tarsals and their dimensions of length, width, and height and assesses which bones and dimensions are most useful for sex determination using a modern skeletal sample (n = 160) comprised of individuals of known sex and age. Summary statistics were calculated for males and females separately to assess the sexual variation for each measure. Pearson’s Correlation Coefficient was used to establish correlations between sex and each measurement. Logistic regression analysis was used to determine the levels of sexual dimorphism in the bones and dimensions for the sample. Accuracy of sex estimations was compared between the left and right sides for each bone to determine if one side was more sexually dimorphic than the other. Logistic regression coefficients from the most accurate bones and dimensions were generated from the sample, which can be used to develop equations to accurately sex other samples of similar Euro-American ancestry. The most sexually dimorphic tarsals were the talus and first cuneiform. Tarsals from the right side were slightly more sexually dimorphic than those from the left. Length and height dimensions were more variable than breadth dimensions. Correct classifications for individual variables were as high as 87.8 %, with the highest overall percentage of correct classification of 93.5% obtained from a combination of all height measurements from the right tarsals for the total sample. This has implications for sexing skeletal remains from archaeological samples when other more commonly used bones are absent or poorly preserved.