Title

Effect of the mode of rehydration on recovery from exercise dehydration: Cardiovascular, hormonal, and medical considerations

Date of Completion

January 2009

Keywords

Health Sciences, Rehabilitation and Therapy

Degree

Ph.D.

Abstract

Several previous studies compare rehydration (REHY) practices during exercise, there is a paucity of research examining dehydration and heat stress recovery following exercise. The purpose of this study was to examine the most common modes of REHY on cardiovascular and thermoregulatory recovery following exercise dehydration (EXDE). Twelve non-heat-acclimatized trained subjects (23±4y, 81.3±3.7kg, 180±6cm, 56.9±4.4mL·min -1·kg-1, 7.8±3.0% body fat) completed 20-h fluid restriction and 2-h EXDE to -4% body mass loss, then were REHY to -2% body mass loss in a randomized, cross-over fashion. REHY methods included no fluid (NF), ad libitum (AL), metered oral (OR), intravenous (IV), and a combination of IV and OR (IV+OR) of half-normal saline (0.45% NaCl). REHY occurred within 30min and subjects were monitored for 30min following. Seated, standing, and mean arterial (MAP) blood pressure (BP) were measured every 15min throughout REHY. Rectal temperature (Trec), skin temperature, HR, and plasma [AVP] were measured throughout REHY. EXDE resulted in overall body mass losses of -4.32 ± 0.22%. REHY returned subjects to -2.13 ± 0.47% for controlled trials. Seated systolic BP was greater for IV+OR compared to OR (p=.015). Seated systolic BP and MAP during REHY showed that, independent of time, IV+OR was greater than OR (p≤.011). Upon standing, IV+OR demonstrated greater BP than both NF (p=.012) and OR (p=.031). The change in systolic BP with the sit-to-stand test was significantly decreased over time with all trials (p≤.036), with no between trial differences (p>.05). NF Trec was significantly greater than IV (p=.023) at REHY30, and significantly greater than OR, IV, and IV+OR (p≤.009), but not AL (p=.068). Mean weighted skin temperature during AL was significantly less than IV+OR at REHY5 (p=.019). HR was reduced more effectively by IV and IV+OR than NF at REHY30 and REHY60 (p<.05). IV+OR plasma [AVP] demonstrated a strong trend for decreasing over time (p=.054) and was significantly less than NF at REHY60 (.003). Following EXDE, short-term cardiovascular and thermoregulatory recovery is most efficiently facilitated with the combined usage of IV+OR, rather than a single REHY method. ^