Journal Title (Medline/Pubmed accepted abbreviation): Int J Sport Nutr Exerc Metab
Page numbers: 300-310
doi (if applicable):
Background: Rapid rehydration during intermittent exercise can aid in combating fatigue and provide optimal cardiovascular function and thermoregulation. Rehydration is physiologically limited by gastric emptying, intestinal absorption, and retention and is also limited by drink palatability. Drink components have been extensively studied to provide the most advantageous rehydration before and during exercise; however, little evidence exists for rehydration during short-term exercise recovery.
Hypothesis/Purpose: The purpose of this study was to evaluate the effectiveness of beverages typically consumed in Hong Kong for rehydration (lemon tea, distilled water, and carbohydrate-electrolyte [CE] drinks) on whole-body rehydration after exercise-induced dehydration.
Subjects: Thirteen well-trained, male runners (mean age, 22.1 ± 3.3 y; weight, 61.2 ± 9.1 kg; maximal oxygen uptake [VO2max ], 64.9 ± 4.0 mL/kg/min; maximal heart rate, 198 ± 7 beats/min) participated in this study.
Experimental design: Cross-over
Treatments and protocol: Each participant completed three 60-minute treadmill runs (at 70% VO2max [determined previously]) separated by ≥ 7 days. A euhydrated state before the run was provided by intake of 500 mL of water the previous night. Following each run, 1 of 3 beverages was consumed once sweating stopped (CE: 109 kJ/100mL, carbohydrate [CHO] 6.6%, sodium 21 mEq/L; sweetened lemon tea: 202 kJ/100mL, CHO 12%, sodium 5 mEq/L; or distilled water). Total fluid intake was 150% of body weight lost during the run in 6 equal portions every 30 minutes. Body weight was determined before and after the run and at 4 hours postexercise (losses regained during recovery were used for rehydration index). Blood samples, expired-air samples, and ratings of perceived exertion were collected at 15-minute intervals during the run. Heart rate was monitored continuously during the run. During the recovery period, urine volume was measured, blood and expired-air samples were collected every hour, and temperature, thirst, abdominal discomfort, and stomach fullness were assessed every 30 minutes. Blood samples were assessed for sodium, potassium, and glucose levels, as well as hemoglobin, hematocrit, plasma volume, and osmolality.
Consumption of CE during recovery from a 60-minute exercise produced the greatest rehydration and least diuretic effect compared with lemon tea and water. However, the differences in CHO concentration between the lemon tea and CE drinks may have affected fluid retention. In addition, the higher sodium concentration in the CE drink may have contributed to its effectiveness. Urine volumes were still high among all groups at study completion and losses after 4 hours may have affected total rehydration. Although lemon tea is popular in Hong Kong, the higher abdominal discomfort (possibly from incomplete CHO absorption) suggests that this beverage should not be recommended to athletes for short-term recovery after exercise.