Hydration status after exercise affect resting metabolic rate and heart rate variability.
BACKGROUND
Heart rate variability and resting metabolic rate are commonly to assess athlete's physiological status and energy requirements. Exercise-induced dehydration can reach up to 5% of body mass per hour. Consequently, dehydration may have a profound physiological effect on human's homeostasis.


OBJECTIVE
To compare the effects of dehydration and rehydration after exercise on heart rate variability and resting metabolic rate in college athletes.


METHODS
14 college athletes were divided into a dehydration group (n=7) and a rehydration group (n=7), both submitted to basal (T1) heart rate variability and resting metabolic rate measurements. After basal measurements both groups were actively dehydrated (-3.4 ± 0.4% of body mass for both groups). Afterwards, dehydration group rested, while rehydration group receive a fluid intake (during a 3 h period) equivalent to 150% of body mass loss achieved during active dehydration. Four hours after active dehydration heart rate variability and resting metabolic rate were re-assessed (T2).


RESULTS
At T2 both rehydration group (+13%) and dehydration group (+30%) achieve a significant (p<0.05) increase in resting metabolic rate, however, only dehydration group ..showed a significant reduction in heart rate variability. More so, the change in resting metabolic rate was significantly higher in dehydration group compared to rehydration group.


CONCLUSIONS
Hydric homeostasis after exercise affects resting metabolic rate and heart rate variability, highlighting the necessity to control hydration state before resting metabolic rate and heart rate variability assessment.
Exercise Science Laboratory, Faculty of Medicine, Universidad Finis Terrae, Santiago, Chile.. m.castro.med@gmail.com.
Mauricio
M
Castro-Sepulveda
School of Medicine, Universidad Mayor, Santiago, Chile.. m.castro.med@gmail.com.
Hugo
H
Cerda-Kohler
Universidad Santo Tomas, San Joaquin, Chile.. m.castro.med@gmail.com.
Cristian
C
Pérez-Luco
Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile.. m.castro.med@gmail.com.
Matías
M
Monsalves
Laboratory of Exercise Sciences, MEDS Sport Medicine Center, Santiago, Chile.. m.castro.med@gmail.com.
David Cristobal
DC
Andrade
Exercise Science Laboratory, Faculty of Medicine, Universidad Finis Terrae, Santiago, Chile.. m.castro.med@gmail.com.
Herman
H
Zbinden-Foncea
Department of Sport and Recreation, University of Playa Ancha, Valparaíso, Chile.. m.castro.med@gmail.com.
Eduardo
E
Báez-San Martín
Department of Physical Activity Sciences, Universidad de Los Lagos, Osorno, Chile. Department of Physical Education, Sport and Recreation, Universidad de La Frontera, Temuco, Chile.. m.castro.med@gmail.com.
Rodrigo
R
Ramírez-Campillo
D056352:Athletes; D001481:Basal Metabolism / Q000502:physiology*; D001835:Body Weight; D003681:Dehydration / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy; D015444:Exercise; D005440:Fluid Therapy; D006339:Heart Rate / Q000502:physiology*; D006706:Homeostasis; D006801:Humans; D008297:Male; D015431:Weight Loss; D055815:Young Adult