Differences in otolith and abdominal viscera graviceptor dynamics: implications for motion sickness and perceived body position.

Human graviceptors, located in the trunk by Mittelstaedt, probably transduce acceleration by abdominal viscera motion. As demonstrated previously in biodynamic vibration and impact tolerance research, the thoraco-abdominal viscera exhibit a resonance at 4 to 6 Hz. Behavioral observations and mechanical models of otolith graviceptor response indicate a phase shift, increasing with frequency between 0.01 and 0.5 Hz. Consequently, the potential exists for intermodality sensory conflict between vestibular and visceral graviceptor signals, at least at the mechanical receptor level. The frequency range of this potential conflict corresponds with the primary frequency range for motion sickness incidence in transportation, in subjects rotated about Earth-horizontal axes (barbecue spit stimulation), and in periodic parabolic flight microgravity research, and also for erroneous perception of vertical oscillations in helicopters. We discuss the implications of this hypothesis for previous self-motion perception research and suggestions for various future studies.

To predict the body's strength.

Although the active and passive strength of the human body has been of interest for many medical and ergonomic problems, it was the emergence of aerospace medicine which required the fundamental and practical studies that provide today's body of data in this field. After the early pioneering years of the 1930's, 1940's and 1950's, the last 25 years brought a maturing of the field of biodynamics, its methods, tools, and theoretical foundations. This overview discusses some of these advances, their contributions to aerospace safety, as well as their applications to the broader areas of traffic safety, orthopedic biodynamics, medicine and ergonomics. To meet future aviation as well as societal challenges, steady efforts by a few centers of excellence are required to integrate operational, experimental, and theoretical advances into sophisticated prediction capabilities.

Effects of proposed preflight adaptation training on eye movements, self-motion perception, and motion sickness: a progress report.

A program has been initiated to develop apparatus and procedures to preadapt astronauts to the sensory rearrangement associated with weightlessness in spaceflight. If space motion sickness is a consequence of adaptation to that sensory rearrangement, preflight training could afford astronauts significant relief from the motion sickness. The preflight adaptation trainer (PAT) was designed to produce rearranged relationships between visual and otolith signals analogous to those experienced in space. Investigations have been undertaken with three prototype trainers. The results indicated that exposure to the PAT sensory rearrangement altered self-motion perception, induced motion sickness, and changed the amplitude and phase of the horizontal eye movements evoked by roll stimulation. However, the changes were inconsistent. Appropriate measures of adaptation and protocols for producing the adaptation efficiently remain to be determined.

Space motion sickness preflight adaptation training: preliminary studies with prototype trainers.

Preflight training frequently has been proposed as a potential solution to the problem of space motion sickness. The paper considers successively the otolith reinterpretation, the concept for a preflight adaptation trainer and the research with the Miami University Seesaw, the Wright Patterson Air-Force Base Dynamic Environment Simulator and the Visually Coupled Airborne Systems Simulator prototype adaptation trainers.

Analysis of the potential association between noise-induced hearing loss and cardiovascular disease in USAF aircrew members.

Questions have been raised concerning the possible impact on health of populations exposed to excessive noise in their work- and leisure-time environments. The purpose of this investigation was to explore the relationship between noise-induced hearing loss and cardiovascular disease by examining the medical records of 2,250 Air Force aircrew members. In this correlative analysis, high-tone hearing loss diagnosed with a high probability of being noise-induced was interpreted as an indirect indicator of noise exposure. Cardiovascular function was measured in terms of recorded systolic and diastolic blood pressure and clinical diagnoses of cardiovascular diseases. Analyses consisted of comparing cardiovascular parameters in maximum and minimum hearing loss groups including polynomial regression curves for blood pressure data, and determining relative risk and attributable risk associated with noise-induced hearing loss for development of cardiovascular disease. Our analyses consistently failed to indicate any association between the degree of noise-induced hearing loss and cardiovascular function in the aircrew population.

The effects of hypokinesia in primates on bone strength.

A 14 days ground based primate hypokinesia investigation was conducted to determine what changes, if any, in bone strength may be demonstrated following 2 weeks cast immobilization and at 14 davs after removal from casts. Controlled compressive loads were applied to vertebral bodies excised from control, 2 weeks immobilization and 2 weeks post immobilization Rhesus monkeys. The material properties reported herein are ultimate load, displacement to ultimate load, stiffness and energy to ultimate load. These results show a decrease in bone strength following immobilization and a still further decrease in bone strength after 14 days.