Abstract
We investigated effect of fluid intake on thermal and cardiovascular responses during 1-h recovery after exercise. Six subjects (five untrained males and one female) cycled (at 60%VO2max) for 60 min in hot-humidity conditions to produce dehydration of 1-2.5% body weight. During the recovery at thermoneutral(at 28°C with rh 40%), the subjects underwent two trials of no fluid (C) and ingested water (F) of 500 ml (containing electrolytes and carbohydrates) after the exercise.We continuously measured weight loss as index of insensible perspiration, tympanic (Tty), rectal (Tre), and skin (Tsk) temperatures, skin blood flow (SkBF), heart rate (HR, included R-R interval), systolic (SBP) and diastolic (DBP) blood pressures, palm sweat rate (SR). Mean arterial pressure (MAP) was calculated as (SBP+2×DBP)/3. Rate-pressure product (RPP) and cutaneous vascular conductance (CVC) calculated HR×SBP and SkBF divided by MAP, respectively. CVC, MAP, SkBF, Tre and mean Tsk were not significantly different between the tests. Insensible perspiration and R-R interval were significantly increased by fluid intake at the early stage. Palm SR and RPP in the F were significantly lowered at the early stage, and stable trend during the recovery, as compared with the C. Tty also decreased in comparison with the C at the initiation of the recovery. The present results suggest that fluid ingestion is reduce thermal and cardiovascular strains after exercise-induced thermal dehydration, and may be to alleviate the autonomic regulatory responses during rehydration in humans. [J Physiol Sci. 2006;56 Suppl:S227]
