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Related Experiment Videos

Reflex heart rate response to variable onset +Gz.

E M Forster1, J E Whinnery

  • 1Rothe Development, Inc., San Antonio, Texas.

Aviation, Space, and Environmental Medicine
|March 1, 1988
PubMed
Summary
This summary is machine-generated.

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Rapid changes in G-force during aerial combat significantly impact heart rate response. Higher onset rates, like very high onset rate (VHOG), lead to a reduced heart rate increase at maximum Gz, indicating an inadequate cardiovascular compensation.

Area of Science:

  • Aerospace Medicine
  • Cardiovascular Physiology
  • Human Factors Engineering

Background:

  • Air combat maneuvering requires rapid tolerance to high sustained Gz forces.
  • The human cardiovascular system often shows inadequate response to these rapid Gz changes.
  • Understanding heart rate dynamics under varying acceleration onset rates is crucial for pilot safety.

Purpose of the Study:

  • To investigate the effect of different onset rates of acceleration on heart rate response.
  • To quantify the cardiovascular response to gradual (GOR), rapid (ROR), and very high onset rate (VHOG) accelerations.
  • To determine if sustained high Gz exposure allows for maximum cardiovascular response.

Main Methods:

  • 81 healthy males were exposed to sustained +7Gz, +8Gz, and +9Gz in a human centrifuge.

Related Experiment Videos

  • Measurements included heart rate (HR) changes during gradual (GOR), rapid (ROR), and very high onset rate (VHOG) accelerations.
  • Time to reach maximum heart rate (T7) and changes in HR at maximum Gz (delta HRA) were analyzed.

    • Main Results:

    • The change in heart rate from rest to maximum Gz (delta HRA) decreased by 50% as onset rate increased from GOR to ROR and VHOG.
    • Maximum heart rate was often not achieved until after the peak Gz level was reached during ROR and VHOG.
    • Heart rate responses to +7Gz, +8Gz, and +9Gz were similar, but very high onset rates (VHOG) showed significantly greater delta HRB than ROR and GOR.

    Conclusions:

    • Rapid onset rates of acceleration significantly attenuate the heart rate increase during sustained high Gz exposure.
    • Sustained exposure to +7Gz to +9Gz for 15 seconds is insufficient for the cardiovascular system to reach its maximum response, especially at very high onset rates.
    • Current acceleration profiles may not fully challenge the cardiovascular system's adaptive capacity, necessitating further research into protective measures.