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

      Limited research suggests that consuming ~10ml/kg of a high Na+ containing beverage (~164mEq Na+/L) prior to physical activity that is 1-4 hours in duration may enhance maintenance of core body temperature in moderately to highly trained males (age 23-46 years).  Based on two studies, high Na+ beverages do not maintain plasma osmolality.  Hyperhydration with water may significantly increase total body water (TBW) thereby lowering plasma osmolality. Limited research is available to evaluate the effectiveness of K+ in beverages consumed before exercise, relevant to hydration maintenance. 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 46 years.

      The comparison between carbohydrate-electrolyte solutions (CES) and non-CES beverages effect on performance was not evaluated in this question. Further research is needed to evaluate optimal fluid and electrolyte intake prior to physical activity/exercise that is 1-4 hours in duration in adults. 

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

       

       

    • Grade: III
      • 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.
    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.
    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.