Engineering topics

Whalen, Robert

Publications and source records attributed to Whalen, Robert.

6 records

NASA NTRS2003

Non-Invasive Investigation of Bone Adaptation in Humans to Cumulative Daily Mechanical Loading

The goal of our research is to better understand the functional relationship between cumulative daily skeletal loading generated by daily activity and the regulation of bone density and bone structure. We have proposed the calcaneus and tibia as useful model bone sites loaded by internal forces in equilibrium with the ground reaction force during gait. The daily history of the ground reaction force is a good relative measure of daily lower limb and calcaneal loading that can be compared to bone density and structure of the calcaneus and cross-sectional geometry of the tibia and fibula. Over the past several years, we have developed image-processing technologies to improve our ability to measure bone density and structure in the calcaneus and lower leg non-invasively with computed tomography and bone densitometry, or DXA. The objective of our current research effort is to determine the accuracy and precision of our CT and DXA image processing methods.

Whalen, Robert↗

NASA NTRS1994

Quantification of Daily Physical Activity

The influence of physical activity on the maintenance and adaptation of musculoskeletal tissue is difficult to assess. Cumulative musculoskeletal loading is hard to quantify and the attributes of the daily tissue loading history affecting bone metabolism have not been completely identified. By monitoring the vertical component of the daily ground reaction force (GRFz), we have an indirect measure of cumulative daily lower limb musculoskeletal loading to correlate with bone density and structure. The objective of this research is to develop instrumentation and methods of analysis to quantify activity level in terms of the daily history of ground reaction forces.

Whalen, Robert↗

NASA NTRS1994

Assessment of Long Bone Flexural Properties from Bone Densitometry

While bone densitometry is the accepted non-invasive method of quantifying bone mineral content in bones, its assessment of bone structural properties is less well understood. The objective of our current work is to compare cross-section shape or areal properties of long bones computed from densitometry data with cross-section flexural properties obtained from surface strain measurements.

Whalen, Robert↗

NASA NTRS1993

Musculoskeletal adaptation to mechanical forces on Earth and in space

A major concern of the US and Russian space programs is the health and safety of astronauts and cosmonauts. One of the areas receiving the most attention has been the effects of long duration space flight on the musculoskeletel system. After three decades of space flight and research, questions continue. Can exercise in space maintain musculoskeletal tissue mass and function in an adult? The objective of this paper is to address this question in a way that hopefully provides a rational basis for quantifying and evaluating the influnence of daily activities on muscle and bone on Earth and in space.

Whalen, Robert↗

NASA NTRS1993

A method for continuous monitoring of the Ground Reaction Force during daily activity

Theoretical models and experimental studies of bone remodeling have identified peak cyclic force levels (or cyclic tissue strain energy density), number of daily loading cycles, and load (strain) rate as possible contributors to bone modeling and remodeling stimulus. To test our theoretical model and further investigate the influence of mechanical forces on bone density, we have focused on the calcaneus as a model site loaded by calcaneal surface tractions which are predominantly determined by the magnitude of the external ground reaction force (GRF).

Whalen, Robert↗

NASA NTRS1993

Bone geometry, structure and mineral distribution using Dual energy X ray Absorptiometry (DXA)

Dual energy x-ray absorptiometry (DXA) is currently the most widely used method of analyzing regional and whole body changes in bone mineral content (BMC) and areal (g/sq cm) bone mineral density (BMD). However, BMC and BMD do not provide direct measures of long bone geometry, structure, or strength nor do regional measurements detect localized changes in other regions of the same bone. The capabilities of DXA can be enhanced significantly by special processing of pixel BMC data which yields cross-sectional geometric and structural information. We have extended this method of analysis in order to develop non-uniform structural beam models of long bones.

Whalen, Robert↗