Hydration

HYD: During Continuous Endurance Exercise (2007)

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

  • Conclusion

     

    Beverages provided in a volume that equals 100% of fluid lost during moderate- to vigorous exercise (65-85% VO2 max), and contain CHO (5.5-15% CHO)* and Na⁺ (55-164 mEq Na)* compared to non-carbohydrate-electrolyte solution (CES) beverages are more effective at maintaining hydration status (including thermoregulatory function) in hydrated young (20 – 35 years) men during 1-4 hours of moderate to vigorous, competitive or recreational activity in moderately hot and humid conditions. The amounts of CHO and Na⁺, as well as the volume of the beverage consumed are important factors for maintenance of hydration during higher-intensity activities, especially in the heat. 

    Care must be taken in choosing a beverage to be consumed during exercise, so as to avoid gastrointestinal distress and/or subjective feelings of discomfort, nausea, and bloating.  Care must also be taken when applying these conclusions beyond the limited populations studied.

    Limited research is available to evaluate the effectiveness of K⁺ in beverages consumed during exercise, relevant to hydration maintenance. Research is needed to determine fluid and electrolyte needs in:   

    • women 
    • pregnant and/or lactating women
    • athletes older than 35 years
    • individuals exercising for prolonged periods of time in cold and/or dry climates.

    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 During Continuous Endurance Physical Activity/Exercise
    • Detail
    • Quality Rating Summary
      For a summary of the Quality Rating results, click here.
    • Worksheets
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  • Search Plan and Results: HYD: Fluid/Electrolyte Needs: During Physical Activity/Exercise 2007