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The use of Meta-analysis to update the whole-body vibration stressor effects within IMPRINT

The use of Meta-analysis to update the whole-body vibration stressor effects within IMPRINT. Gareth Conway James Szalma MIT 2 Lab, University of Central Florida. Whole-body vibration (WBV) effects on performance. Why is it a problem?

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The use of Meta-analysis to update the whole-body vibration stressor effects within IMPRINT

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  1. The use of Meta-analysis to update the whole-body vibration stressor effects within IMPRINT Gareth Conway James Szalma MIT2 Lab, University of Central Florida MIT2 Lab, UCF

  2. Whole-body vibration (WBV) effects on performance • Why is it a problem? • Enemies do not confront US forces directly – moved from the battlefield to urban environments. Hit and then go to ground and/or blend in with the population • Need to utilize technological advantages in the areas of mobility and information • The US Army has the advantage, but… MIT2 Lab, UCF

  3. WBV effects on performance – the Soldier’s perspective On in-vehicle display units: “the screens are almost impossible to read during periods of WBV and usually require the driver to stop to enable reading or precision data entry”. On weapons systems: “Vibrations created by firing a round from a tank or howitzer often creates momentary disorientation….. Targets often have to be re-acquainted and engagement decisions re-established”. “Extensive WBV makes even the simplest task extremely difficult”. MIT2 Lab, UCF

  4. A few Questions & Answers What is it? • “A mechanical wave, that transfers energy but no matter” (Mansfield, 2004). Who does it affect? • Anyone supported by a vibrating surface What does is it affect (intuitively)? • Mainly sensory (input) & motor (output) processes, though may influence central processing also. MIT2 Lab, UCF

  5. WBV is bad, so what is the issue? • Everybody knows that vibration is bad for performance…. • However, the effects of WBV are highly variable, with the effects moderated by a range of other factors: - Vibration characteristics (axes, frequency, magnitude, etc) - Exposure duration. - The type of dependent variable used (i.e., IMPRINT task taxon framework). MIT2 Lab, UCF

  6. Methods • Systematic search for empirical literature. - database searches - web-based searches - checking reference lists of articles acquired - subject matter experts consulted • 224 papers identified. MIT2 Lab, UCF

  7. Inclusion Criteria • Empirical examination of the application of WBV. • Use of at least one measure of performance. • Examination of DIRECT effects on performance. • Utilization of a ‘zero-WBV’ control group. • Sufficient information/data from which to calculate effect sizes. - 13 studies accepted, and coded. - the literature more sparse than we expected. MIT2 Lab, UCF

  8. Results • Effect sizes – negative values reflect performance decrements under WBV conditions, when compared to control conditions. • Cohen’s d: - 0.2 = ‘small effect’ - 0.5 = ‘medium effect’ - 0.8 = ‘large effect’ • Large global effect of WBV on performance (d = -0.95). MIT2 Lab, UCF

  9. Effect of dependent variable type (IMPRINT Taxon) MIT2 Lab, UCF

  10. Effect of measure type MIT2 Lab, UCF

  11. Effect of intensity MIT2 Lab, UCF

  12. Effect of frequency MIT2 Lab, UCF

  13. Effect of exposure duration MIT2 Lab, UCF

  14. Effect of duration by intensity MIT2 Lab, UCF

  15. Conclusions • Vibration does indeed act to degrade most goal-directed activities. • Most clear effects are on motoric tasks (fine motor continuous especially). • Interactions with other stressors? MIT2 Lab, UCF

  16. Further conclusions & Implications • Surprising lack of empirical research that met the criteria for inclusion. • The data are what they are…. • Importance of future methodologically and theoretically rigorous research in order to ‘fill in the gaps’. • May need to consider the effect of WBV when designing smaller technologies – importance of testing these with stressors present. MIT2 Lab, UCF

  17. What now? • Ongoing meta-analyses – Noise & speech effects on performance – Time pressure effects on performance • Updates to the Thermal and the Vibration meta-analyses (updated searches, identifying and contacting research groups, etc). MIT2 Lab, UCF

  18. Acknowledgements The views expressed here are those of the authors and do not necessarily reflect the official policy or position of the Department of the Army, the Department of Defense, or any official agency of the United States government. This work was supported by a sub-contract through Micro-Analysis and Design (MAAD) from the Human Research Engineering Directorate, Army Research Laboratory (HRED-ARL), P.A. Hancock, Principal Investigator (Grant #64018042). We wish to thank John Lockett, Laurel Allender, Celine Richer and Sue Archer, for providing their administrative and technical direction for this Grant. We also thank Dr Bob Kennedy for his insightful discussions on vibration. MIT2 Lab, UCF

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