Exercise and heat orthostatism and the effect of heat acclimation and physical fitness

E. Shvartz, A. Meroz, A. Magazanik, Y. Shoenfeld, Y. Shapiro

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14 Scopus citations

Abstract

Twelve trained and 16 untrained young men were administered 5 orthostatic tests while leaning upright against a wall: for 20 min before exercise; after 60 min of exercise at a load of 40 W; after 15 min of exercise at a load of 80 W; after a V(o 2) max test; and after 3 hr of exercise at a load of 40 W in heat (39.4°C DB, 30.3°C WB). Eight of the untrained subjects were retested in the 5 orthostatic tests after 8 d of heat acclimation. The number of fainters in the orthostatic tests administered before exercise, after exercise at 40 W and 80 W, and after exercise in heat, were 3, 4, 6, and 13, respectively. There were no fainting episodes after the V(o 2) max tests. Orthostatic responses in the different conditions were partially related. The trained subjects showed substantially better responses than the untrained ones (10% vs. 25% of fainting episodes), and heat acclimation resulted in marked improvement in orthostatism (decrease to 5% faintings). The results show that V(o 2) max and heat tolerance account for most of the variability which determines orthostatic tolerance.

Original languageEnglish
Pages (from-to)836-842
Number of pages7
JournalAviation Space and Environmental Medicine
Volume48
Issue number9
StatePublished - 1977

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