Determining the complex relationship between cellular and macroscopic responses requires an integrated biomechanics approach consisting of several simultaneous rigorous engineering experimental and theoretical analyses.  Specifically, we correlate real-world loads to in situ or in vivo  tissue deformation responses using innovative imaging techniques and physical models.  We measure tissue mechanical properties on the organ and determine theoretical constitutive relationships.  We have incorporated these constitutive relationships in theoretical models which are developed and validated with imaging, animal experiments, and physical model data.  The load tolerances associated with reversible and irreversible injuries are determined experimentally on a cellular, tissue or whole animal level.  Finally, we perform integrated analyses using the theoretical models to predict the interactions between the loads applied to the whole body, tissue mechanical properties, and the response of the tissues and cells in children and adults.  This information is essential for the design and development of effective methods for injury prevention and treatment.