Biodynamics--the key to flight.

Biodynamics measures the effects of mechanical force on living tissues. The quantitative relations of mechanical stress factors and biological strain responses of the living body provide criteria for limits of injury threshold, reversible injury, permanently disabling injury, and fatal injury. These criteria are guidelines for aerospace design and performance standards involving human survival in the environment of flight. Below these limits, the effects of mechanical force factors on human performance while acutely or chronically exposed to them in aerial or space flight are crucial. Some can be accumulatively disabling; others can be adapted to over a period of time. Extremes of low-frequency vibration cannot be long endured, while sustained zero gravity in space flight produces mild, transient malaise followed by adaptation in several hours. Aerospace flight biodynamics deals with human reactions to absence of gravity; sustained curvilinear acceleration; sustained acceleration and deceleration (launch and reentry in space flight); single impact force (collisions); low-frequency vibration in the whole human body resonance response range; whole-body tumbling and spinning, as in high-altitude free-fall; acoustical range vibrations; explosive blast in air or water; abrupt decompression, as in cabin pressure failure; static forces in tension, compression, torsion and shear. Biodynamic stress analysis takes into account whole-body responses, particular responses of rigid bone, viscous elastic soft tissues, pneumatic and hydraulic effects of gas and fluids in hollow organs, and displacements of solid organs suspended in body cavities. Accurate and comprehensive results require physical measurements, clinical and laboratory studies before and after exposure, subjective reports of trained volunteer subjects, and objective medical and bioengineering evaluation of results.(ABSTRACT TRUNCATED AT 250 WORDS)