Mechanisms of Whole-Body Vibration Effects on Human Performance

Oscillatory ship motion and vibration effects on crews in modern naval air and sea systems can be the limiting factor in mission performance. The mechanisms of these effects, however, have not yet been clearly delineated; nor have a practical taxonomy and standard methodology for distinguishing and evaluating the deleterious action of whole-body vibratory motion on human performance been established. Some effects of vibration on performance appear to be directly attributable to immediate mechanical disruption of input and /or output (i.e., interference at the points of contact—displays or controls—between operator and task). Far more meager is clear evidence for time-dependent disruptive or degrading effects of vibration on central cognitive processes: these of course may also be affected indirectly by changes in the physiological state (including motion sickness and fatigue) induced by the motion or vibration. The distinction between direct and indirect mechanisms of performance decrement in the motion environment has important implications for both protective measures and the focus of future research. This report considers published work on the performance effects of vibration in relation to the etiology of performance change and those implications. A critical review of the methodology of performance studies in motion and vibration environments is under way at the Naval Biodynamics Laboratory; and a series of experiments (some previously published) on whole-body vibration effects on performance is also in progress. While the duality of the mechanisms of action of oscillatory motion on performance remains an open question, the evidence so far adduced for other than direct mechanical effects is sparse, at least in the frequency range of major body resonance phenomena. Further experimentation, including long-duration studies, is needed to resolve this question. Implications both for future research directions and for current national and international standardization efforts in this area are discussed.