Effect of a carbohydrate-electrolyte beverage, lemon tea, or water on rehydration during short-term recovery from exercise


Journal Title (Medline/Pubmed accepted abbreviation): Int J Sport Nutr Exerc Metab
Year: 2011
Volume: 21
Number: 4
Page numbers: 300-310
doi (if applicable):

Summary of background and research design:

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.


Summary of research findings:
  • Body weight loss was ~2.0% and plasma volume decreased ~10% after the run, without differences between sessions.
  • Volume of fluid retained from the drink was highest among the CE group (52%) compared with the lemon tea group (36%) and the water group (30%).
    • Urine output was lowest in the CE group (638 mL; primarily in the last hour of recovery) compared with the lemon tea group (921 mL) and water group (915 mL) who had peak urine production in the third hour.
  • Replacement of body fluid loss was also highest among the CE group (77%) compared with the lemon tea group (54%) and the water group (46%).
  • Plasma volume after recovery increased from baseline in the CE group (11.2%) and was significantly higher than volumes in the lemon tea (–3.1%) and water groups (0.2%; P < .05 for both).
  • Plasma osmolality increased after the run and returned closer to baseline in the lemon tea group compared with the CE and water groups.
  • Glucose levels increased in the lemon tea group and remained elevated throughout recovery; similar increases were observed in the CE group, but glucose levels returned to baseline by recovery end (no changes were observed in the water group).
  • Sodium levels decreased consistently in the water group, but first decreased, then increased somewhat in the CE and lemon tea groups without difference between these 2 groups.
  • There were no differences between the groups for potassium levels, temperature, and ratings of perceived exertion and thirst.
    • Higher abdominal discomfort in the last 2 hours of recovery was reported in the lemon tea group compared with the other 2 groups.
    • Higher stomach fullness and bloating was also reported in the lemon tea group.

Interpretation of findings/Key practice applications:

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.

 
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