Key result
Partial water immersion increases headward acceleration tolerance by ~2.8 G for heart rate versus control.
Why the study?
Protection against the effects of headward acceleration by immersion in water and its physiological impact on vision, ear pulse, and heart rate were assessed to understand tolerance mechanisms.
Does partial immersion in water improve tolerance to headward acceleration in healthy men?
Does partial immersion in water improve tolerance to headward acceleration in healthy men?
Water immersion provides significant protection against the physiological effects of headward acceleration, challenging the concept that impediment to venous return is the primary determinant of acceleration tolerance.
Water immersion may enhance experimental headward acceleration tolerance; leaves open clinical translation and venous return mechanism confirmation.
Protection against the effects of headward acceleration afforded by immersion in water has been assayed in the human centrifuge on 15 trained subjects. Immersion in water to the xyphoid afforded an average protection of 1.1 ± 0.1 G for vision and ear opacity and of 1.6 ± 0.2 G for ear pulse and heart rate. Deeper immersion, to the level of the third rib at the sternum increased the protection to 1.8 ± 0.1 G for vision and ear opacity and to 2.8 ± 0.2 G for ear pulse and heart rate. The protection afforded the various physiologic variables increased with the magnitude of acceleration tested. Protection against loss of consciousness may be greater than protection against blackout and is probably similar to the protection afforded the ear pulse and heart rate. The cardiovascular reactions produced by headward acceleration are qualitatively similar with and without water immersion. This finding does not support the concept that impediment to venous return is the primary determinant of man's tolerance to headward acceleration. Visual symptoms occurred at greater amplitudes of ear pulse, and presumably also at greater blood pressures at head level, during water immersion than during control runs. vision; arterial pressure; heart rate; venous return; arterial pulse in ear Submitted on May 13, 1963
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Wood et al. (1963) studied Healthy (n=15). Partial immersion in water vs. Without water immersion was evaluated on Protection against the effects of headward acceleration (G tolerance). Partial immersion in water to the third rib increased tolerance to headward acceleration by 1.8 G for vision and 2.8 G for heart rate compared to control runs.
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