Exercise and FluidExercise and FluidReplacementReplacementACSM Position Stand 2007

EvidenceEvidenceSustained exercise can elicit high

sweat rates and substantial water and electrolyte losses, particularly in warm-hot weather.

EvidenceEvidenceThere is considerable variability

for water and electrolyte losses between individuals and between different activities.

EvidenceEvidenceIf sweat water and electrolyte

losses are not replaced, then the person will dehydrate.

Exercise and FluidExercise and FluidReplacementReplacementThe goal of prehydrating is to

start the activity euhydrated and with normal plasma electrolyte levels.

Exercise and FluidExercise and FluidReplacementReplacementPrehydrating with beverages, in

addition to normal meals and fluid intake, should be initiated when needed at least several hours before the activity to enable fluid absorption and allow urine output to return to normal levels.

Exercise and FluidExercise and FluidReplacementReplacementThe goal of drinking during

exercise is to prevent excessive (92% body weight loss from water deficit) dehydration and excessive changes in electrolyte balance to avert compromised performance.

Exercise and FluidExercise and FluidReplacementReplacementBecause there is considerable

variability in sweating rates and sweat electrolyte content between individuals, customized fluid replacement programs are recommended.

Exercise and FluidExercise and FluidReplacementReplacementIndividual sweat

rates can be estimated by measuring body weight before and after exercise.

EvidenceEvidenceIndividuals can monitor their

hydration status by employing simple urine and body weight measurements.

Several days of first morning body weights can be used to establish base-line body weights that represent euhydration.

EvidenceEvidenceBody weight changes can reflect

sweat losses during exercise and can be used to calculate individual fluid replacement needs for specific exercise and environmental conditions.

EvidenceEvidenceDehydration increases

physiologic strain and perceived effort to perform the same exercise task, and this is accentuated in warm-hot weather.

EvidenceEvidenceDehydration (92% BW) can

degrade aerobic exercise performance, especially in warm-hot weather.

EvidenceEvidenceThe greater the dehydration level

the greater the physiologic strain and aerobic exercise performance decrement.

EvidenceEvidenceDehydration (92% BW) might

degrade mental/cognitive performance.

EvidenceEvidenceDehydration (3% BW) has

marginal influence on degrading aerobic exercise performance when cold stress is present.

EvidenceEvidenceDehydration (3–5% BW) does not

degrade either anaerobic performance or muscular strength.

EvidenceEvidenceThe critical water deficit and the

magnitude of exercise performance degradation are related to the heat stress, exercise task, and the individual`s unique biological characteristics.

EvidenceEvidenceHyperhydration agents can be

achieved by several methods, but provides equivocal benefits and has several disadvantages.

Exercise and FluidExercise and FluidReplacementReplacementDuring exercise, consuming

beverages containing electrolytes and carbohydrates can provide benefits over water alone under certain circumstances.

EvidenceEvidenceDehydration is a risk factor for

both heat exhaustion and exertional heat stroke.

EvidenceEvidenceDehydration can increase the

likelihood or severity of acute renal failure consequent to exertional rhabdomyolysis.

EvidenceEvidenceDehydration and sodium deficits

are associated with skeletal muscle cramps.

EvidenceEvidenceSymptomatic exercise-associated

hyponatremia (low plasma sodium levels) can occur in endurance events.

EvidenceEvidenceFluid consumption that exceeds

sweating rate is the primary factor leading to exercise-associated hyponatremia.

EvidenceEvidenceLarge sweat sodium losses and

small body mass (and total body water) can contribute to the exercise-associated hyponatremia.

EvidenceEvidenceWomen generally have lower

sweating rates than men.

EvidenceEvidenceSex differences in renal water

and electrolyte retention are subtle and probably not of consequence.

EvidenceEvidenceWomen are at greater risk than

men to develop exercise-associated symptomatic hyponatremia.

EvidenceEvidenceOlder adults have age-related

decreased thirst sensitivity when dehydrated making them slower to voluntary reestablish euhydration.

EvidenceEvidenceOlder adults have age-related

slower renal responses to water and sodium loads and may be at greater risk for hyponatremia

EvidenceEvidenceChildren have lower sweating

rates than adults.

EvidenceEvidenceMeal consumption promotes

euhydration.

EvidenceEvidenceSweat electrolyte (sodium and

potassium) losses should be fully replaced to reestablish euhydration.

EvidenceEvidenceCaffeine consumption will not

markedly alter daily urine output or hydration status.

EvidenceEvidenceAlcohol consumption can

increase urine output and delay full rehydration.

Exercise and FluidExercise and FluidReplacementReplacementAfter exercise, the goal is to

replace any fluid electrolyte deficit.

Exercise and FluidExercise and FluidReplacementReplacementThe speed with which

rehydration is needed and the magnitude of fluid electrolyte deficits will determine if an aggressive replacement program is merited.

RecommendationsRecommendationsPrehydrating with beverages, if

needed, should be initiated at least several hours before the exercise task to enable fluid absorption and allow urine output to return toward normal levels.

RecommendationsRecommendationsConsuming beverages with

sodium and/or salted snacks or small meals with beverages can help stimulate thirst and retain needed fluids.

During ExerciseDuring ExerciseThe goal of drinking

during exercise is to prevent excessive dehydration (92% BW loss from water deficit) and excessive changes in electrolyte balance to avert compromised exercise performance.

During ExerciseDuring ExerciseThe amount and rate of fluid

replacement depends upon the individual sweating rate, exercise duration, and opportunities to drink.

During ExerciseDuring ExerciseIndividuals should periodically

drink (as opportunities allow) during exercise, if it is expected they will become excessively dehydrated.