Effect of longitudinal physical training and water immersion on orthostatic tolerance in men.
To test the hypothesis that moderately intense physical training has no effect on orthostasis, orthostatic and fluid-electrolyte-endocrine responses to 60 degrees head-up tilt were compared before and after 6 h of water immersion (34.5 +/- 0.1 degrees C) up to the neck following 6 months of exercise training. During the tilt test the five male subjects (27-42 years) each wore a lower-body positive-pressure suit (MAST-111A antishock trousers). The tilt procedure consisted of a 40-min supine control period (suit deflated), followed by a maximum 90-min tilt period (suit inflated to 50 +/- 5 mm Hg for 30 min, then deflated for 60 min or until presyncope). The mean +/- S.E. pretraining cycle ergometer peak VO2 was 3.20 +/- 0.14 L.min-1 (39 +/- 2 ml.min-1.kg-1), 3.36 +/- 0.27 L.min-1 (42 +/- 4 ml.min-1.kg-1) after 3 months (N.S.), and increased by 18% to 3.78 +/- 0.36 L.min-1 (48 +/- 5 ml.min-1.kg-1, +22%, p less than 0.05) posttraining. During pretraining, water immersion tilt tolerance decreased from 74 +/- 16 min before to 34 +/- 9 min (delta = 40 min, p less than 0.05) after immersion. During posttraining, water immersion tilt tolerance decreased similarly from 74 +/- 16 min preimmersion to 44 +/- 13 min (delta = 30 min, p less than 0.05) postimmersion (74 vs. 74 min, N.S.; 34 vs. 44 min, N.S.).(ABSTRACT TRUNCATED AT 250 WORDS)
Greenleaf
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Space Physiology Branch, NASA Ames Research Center, Moffett Field, CA 94035.
Dunn
E R
ER
Nesvig
C
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Keil
L C
LC
Harrison
M H
MH
Geelen
G
G
Kravik
S E
SE
D000328:Adult; D001794:Blood Pressure; D005676:Gravity Suits; D006339:Heart Rate; D006400:Hematocrit; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007024:Hypotension, Orthostatic / Q000517:prevention & control*; D007101:Immersion; D008297:Male; D010101:Oxygen Consumption; D010806:Physical Education and Training; D011188:Potassium / Q000097:blood; D011312:Pressure; D012083:Renin / Q000097:blood; D012964:Sodium / Q000097:blood; D014667:Vasopressins / Q000097:blood
D006454:Hemoglobins; D014667:Vasopressins; D012964:Sodium; D012083:Renin; D011188:Potassium