Hydration & Electrolytes - Sports Nutrition - Fall 25

What % of the adult body weight is water

60

What % of of muscle is water

70-75

Water an electrolytes serve a critical role in maintain what 3 things?

Cardiovascular function, Thermoregulation, Blood volume

2nd only to oxygen in necessity for maintaining life

Water

What % loss in body mass from fluid loss can be fatal

9-12

Average amounts of body water in males and females

Males = 42L, Females = 30L

True or False: There is enough evidence to establish water intake

recommendations for each population or sport

False

Adequate intake for total daily water intake (from food and beverages) for healthy, sedentary males and females in temperate climates

Males = 3.7L, Females = 2.7L

What population holds more body water relative to weight

Young adults

Which gender holds more body water?

Male

Individuals with which body composition hold more water?

Leaner people

2 Components of Total Body Water

Intracellular and extracellular fluid

2 Components of Extracellular fluid

Interstitial fluid and plasma

Fluid inside the cell membrane

Intracellular Fluid

Fluid outside the cell membrane

Extracellular fluid

Fluid between the cells of the body

Interstitial fluid

Fluid part of blood

Plasma

3 Ways Water Intake Occurs

Fluid intake, food intake, metabolic processes

3 Ways Fluid Loss Occurs

Excretion from kidneys (urination), evaporation from skin and respiratory tract, feces

Process of losing body water

Dehydration

Overly dehydrated

Hypohydration

Adequately hydrated

Euhydration

Overly hydrated

Hyperhydration

Critical mechanism to prevent excessive increase in body temperature

Sweating

Sweat rates per hour

1-1.5 L/hr

True or False: A loss of 2-6% of body weight is not uncommon when sweating

True

Dangerously low blood sodium levels

Hyponatremia

True or False: In general, water intake does not need to be precisely & perfectly matched to water loss

True

Acts on collecting ducts within the kidney making them more permeable to water

ADH (aka Vasopressin)

ADH is stimulated by changes in what 2 things

Plasma osmolarity and plasma volume

Function of ADH

Promotes reabsorption of water by the kidneys

Large loss of Na & Cl in sweat results in the release of what?

Aldosterone

Function of aldosterone

Promotes increased retention of Na and Cl by the kidneys

3 Functions of Electrolytes

Regulate water balance, Regulate fluid exchange within the body’s fluid compartments, Essential for muscle contraction and nerve conduction

Major salt lost in sweat and is most important electrolyte to replace

following exercise

Sodium chloride

Recommendation for sodium per day

Less than 2,300 mg

Average daily intake of sodium in males and females

Males = 4,400 mg, Females = 3,090

Makes up for 77% of sodium in American diet

Processed foods

Abundant in unprocessed foods such as fruits and vegetables, whole grains, and milk

Potassium

Recommended potassium intake

4,700mg

Average daily intake of potassium in US

2,640

#1 cause for fatigue

Hypohydration

Is not felt until 2% loss in body mass from fluid

Thirst

Single bouts of anaerobic work (less than 40-s) have typically shown what in performance with dehydration

Minimal effects

Repeated bouts of anaerobic exercise typically show what in performance with dehydration

Significant decrease 

2 Ways to Monitor Hydration Status

Plasma osmolarity and Urine analysis

1 L of water lost is equivalent to how many kg

1 (2.2 Ibs)

How many L of water should you drink for each kg of body weight lost

1-1.5L