Electrolytes

Electrolytes are charged minerals in body fluids that regulate fluid balance and distribution, cellular metabolism and neuromuscular function.^{1International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 506.} Sodium, calcium, chloride and bicarbonate are the main electrolytes outside cells.^{1International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 506.}

Sweat losses include sodium chloride and smaller amounts of potassium, magnesium and calcium.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 213.} These minerals support muscle contraction and nerve conduction, and sodium helps the body retain the fluid a client drinks.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 213.} Sweat sodium varies widely between people, from 0.2 to more than 12.5 g per liter.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 213.}

In practice

Clients who lose a lot of salt in sweat may need higher-sodium foods, salt added to meals or electrolytes added to sports drinks.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 213.}

Drinking only water or a low-sodium drink during long, hard sessions can dilute blood sodium to dangerous levels, called hyponatremia.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 213.} To avoid it, clients shouldn’t drink more than they sweat or weigh more after a session than before it, and should get sodium from food or drinks.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 213.} For events involving many hours of sweating, ACSM recommends an individual hydration plan.^{3Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 507.}

For prolonged activity in the heat, the IPTA textbook recommends drinks containing about 20 to 30 mEq/L of sodium, 2 to 5 mEq/L of potassium and 5 to 10% carbohydrate.^{4International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 508.} Sports drinks supply little potassium; foods such as tomatoes, citrus fruits, melons, potatoes, bananas and milk provide more of this mineral.^{5Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 214.}