Hydration

HYD: After Continuous Endurance Exercise (2007)

• Assessment
  What fluid and electrolytes are needed after continuous endurance physical activity/exercise of 1-4 hours in duration in adults (19 years or older) to restore hydration?

  • Conclusion

    Rehydration beverages provided in a volume that equals 100-150% of fluid lost during exercise, and contain CHO (6-7.6% CHO)* and Na⁺ (57.5-1150 mg per dL Na⁺)* are more effective at improving hydration status and endurance capacity than non-carbohydrate electrolyte solution (CES) beverages provided in volumes of less than 100% of fluid lost by young (20 – 35 years) men following 1-2 hours of moderate to vigorous (60-70% VO2 max), competitive or recreational activity. Limited research is available to evaluate the effectiveness of K⁺ in rehydration beverages.  Furthermore data is not available to evaluate effectiveness of rehydration beverages beyond two hours of physical activity. Both the amount of Na⁺ and the volume of the solution consumed are important factors for rehydration after prolonged exercise.

    Care must be taken when applying these conclusions beyond the limited populations studied. Research is needed to determine fluid and electrolyte needs in:

    • women
    • pregnant and/or lactating women
    • athletes older than 35 years
    • individuals exercising for periods of 2-4 hours.

    The effect of CHO and Na⁺ in excess of the upper range (7.6% and 1150mg per dL, respectively)* were not evaluated in these studies. The comparison between CES and non-CES beverages effect on performance was not evaluated in this question. 

    * See Conversion Table for information on converting mmol to mEq and mg and % CHO to grams.

  • Grade: II
    • Grade I means there is Good/Strong evidence supporting the statement;
    • Grade II is Fair;
    • Grade III is Limited/Weak;
    • Grade IV is Expert Opinion Only;
    • Grade V is Not Assignable.
    • High (A) means we are very confident that the true effect lies close to that of the estimate of the effect;
    • Moderate (B) means we are moderately confident in the effect estimate;
    • Low (C) means our confidence in the effect estimate is limited;
    • Very Low (D) means we have very little confidence in the effect estimate.
    • Ungraded means a grade is not assignable.
  • Evidence Summary: Fluid and Electrolyte Needs After Continuous Endurance Physical Activity/Exercise
    • Detail
    • Quality Rating Summary
      For a summary of the Quality Rating results, click here.
    • Worksheets
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      • Wong SH, Williams C, Simpson M, Ogaki T. Influence of fluidintake pattern on short-term recovery from prolonged, submaximal running and subsequent exercise capacity.  Journal of Sports Sciences 1998; 16: 143-52.
  • Search Plan and Results: HYD: Fluid/Electrolyte Needs: After Physical Activity 2007