Much of the difficulty in determining the time since death stems from the lack of systematic observation and research on the decomposition rate of the human body. Continuing studies conducted at the University of Tennessee, Knoxville, provide useful information on the impact of carrion insect activity, ambient temperature, rainfall, clothing, burial and depth, carnivores, bodily trauma, body weight, and the surface with which the body is in contact. This paper reports findings and observations accumulated during eight years of research and case studies that may clarify some of the questions concerning bodily decay.

Rising to a standing position from a sitting position is one of the most important activities of daily life. We present a total-body analysis of rising from a chair as performed by nine healthy individuals under controlled conditions. We describe four phases of this activity. Phase I is a flexion-momentum phase used to generate the initial momentum for rising. Phase II begins as the individual leaves the chair seat and ends at maximal ankle dorsiflexion. Forward momentum of the upper body is transferred to forward and upward momentum of the total body. Phase III is an extension phase during which the body rises to its full upright position. Phase IV is a stabilization phase. Kinetics and kinematics of the phases are analyzed. The phases are differentiated in terms of momentum and stability characteristics. Clinical implications of the mechanics of rising are discussed.

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The pressures on human articular cartilage have been measured in vivo. An instrumented femoral head prosthesis that telemeters interarticular pressure at 10 discrete locations 253 times per second was implanted in apposition to natural acetabular cartilage. Data were acquired during surgery, recovery, rehabilitation, and normal activity, for longer than 1 year after surgery. Pressure magnitudes were synchronized with body-segment kinematic data and foot-floor force measurements so as to locate transduced pressure areas on the natural acetabulum and correlate movement kinematics and dynamics with local cartilage pressures. The data reveal very high local (up to 18 MPa) and nonuniform pressures, with abrupt spatial and temporal gradients, that correlate well both in magnitude and distribution with in vitro data and computer simulations of synovial joint mechanics. Peak pressures in vivo are, however, considerably higher than pressures measured in vitro under the putative forces experienced by the joint in life, particularly in normal movements where cocontraction occurs in agonist and antagonist muscles across the hip joint. Thus, extant gait-analysis studies which apply inverse Newtonian calculations to infer joint forces establish the lower limit on such forces, since such analyses include only the net muscular torques about the joint and cannot account for the contribution of the increment in joint force due to muscular cocontraction. Our data also contribute to the understanding of normal synovial joint tribology and the possible role of mechanical factors in the deterioration evident in osteoarthritis. Further, design criteria for both partial and total hip replacement prostheses and specific aspects of rehabilitation protocols following hip surgery (e.g., the extent to which crutches and canes unload the hip joint) warrant reconsideration in light of the extraordinary high pressures measured during the activities of daily living.The maximum resultant force across the human hip joint during walking and running had been first estimated (1-3) and then measured in vivo (4-6) at from 2.5 to 5.8 times body weight, but the local pressures and pressure distribution between opposing cartilage layers in life have not been reported. Such knowledge is essential to understanding the physiology and pathology of human articular cartilage. How the opposing thin (1-3 mm) layers of articular cartilage in synovialjoints distribute high loads across matingjoint areas is essential to understanding the remarkable tribology (7) of normaljoints-high load carriage, low coefficients of friction (0.01-0.002), and long life-and may illuminate the role of mechanical factors in the etiology of osteoarthritis. Current opinion on the pathogenesis of this widely prevalent [estimated to afflict more than forty-million persons in the United States in 1962-64 (8)] and frequently incapacitating chronic disease (9) implicates focal mechanical stress on or in