Related Experiment Videos
The effect of varying time at -Gz on subsequent +Gz physiological tolerance (push-pull effect)
R D Banks1, J D Grissett, P L Saunders
1Defence and Civil Institute of Environmental Medicine, North York, Ont., Canada.
Aviation, Space, and Environmental Medicine
|August 1, 1995
Summary
The push-pull effect, a decrease in Gz tolerance, is worsened by longer exposure to negative Gz ( -Gz). Increasing the duration of -Gz exposure before positive Gz (+Gz) significantly reduces blood pressure and increases visual light loss.
Area of Science:
- Aerospace Medicine
- Human Physiology
- Biomedical Engineering
Background:
- Previous research indicates reduced +Gz tolerance after 0 Gz or -Gz exposure, known as the push-pull effect.
- The impact of varying durations of -Gz exposure on this effect requires further investigation.
Purpose of the Study:
- To investigate how different durations of -2 Gz exposure influence the push-pull effect.
- To quantify the physiological responses to varying -Gz exposure times preceding +2.25 Gz.
Main Methods:
- Six subjects underwent relaxed exposures to +2.25 Gz on the Coriolis Acceleration Platform (CAP).
- Experimental runs involved preceding +2.25 Gz exposure with -2 Gz for 2, 5, or 15 seconds.
- Blood pressure (BP) and visual light loss were monitored during exposures.
Main Results:
- Mean BP significantly decreased following -2 Gz exposure compared to control runs.
- A 15-second exposure to -2 Gz resulted in a greater and slower-recovering BP reduction than 2 or 5-second exposures.
- Incidents of visual light loss increased with longer -Gz exposure durations (1, 2, and 4 incidents for 2, 5, and 15 seconds, respectively).
Conclusions:
- The push-pull effect is amplified by increasing the duration of preceding -Gz exposure under relaxed conditions.
- Longer -Gz exposure durations lead to more pronounced cardiovascular and visual disturbances.