Exercise in a warm condition enhances plasma volume expansion compared to a cool condition with an increased skin but not core temperature

Abstract

Plasma volume (PV) expansion is a fundamental physiological adaptation to exercise‐heat acclimation. We investigated the effects of an increased body core temperature and skin temperatures on PV expansion after intense exercise.METHODSEight healthy young men underwent two identical trials which differs only ambient temperature (Ta) during exercise. On day 1, baseline blood sample was taken in a thermoneutral condition, then they performed a 72‐min intense‐intermittent exercise (8 sets of 4 min at 80% VO2max – 5 min at 20% VO2max) under cool (Ta of 20°C) and warm (Ta of 30°C) conditions. On day 2, after 23 hours after exercise, blood sample was taken again in the thermoneutral condition. We measured hematocrit, hemoglobin concentration, and plasma albumin and protein concentrations, and from these data, percent change in PV (Δ%PV) and in plasma albumin and total protein content (Δ%Albcont and Δ%TPcont, respectively) from baseline were determined. Esophageal temperature (Tes) and mean skin temperature (Tsk) were measured during exercise.RESULTSDuring exercise, Tsk were higher (p < 0.05) in warm than cool condition while Tes was comparable between trials. Δ%PV was higher in warm condition than cool condition (6.8 ± 1.3 % and 3.3 ± 1.3 %, means ± SE, p < 0.05), Δ%Albcont and Δ%TPcont were also higher in warm condition than cool condition (both, p < 0.05).CONCLUSIONSExercise in a warm condition enhances plasma volume expansion with plasma protein content after intense exercise compared with a cool condition, which is associated with an increased skin temperatures but not core temperature. Thus, increase in skin temperatures would be a possible target to enhance physiological adaptation to exercise‐heat acclimation.Support or Funding InformationThis work was supported by a Grant‐in‐Aid for Scientific Research (B) and a Grant‐in‐Aid for Challenging Exploratory Research (K. Okazaki) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.