+ Nutrition
and More

By Kate Fisher

Kate Fischer, MS, RD, LD owns Alameda Fitness
Center in Northeast
Portland, OR
503-548-4011
getfit@alamedafitness.
www.alamedafitness.com

Sweat: What, Why, and How to Replace It?

Homemade Sports Drink Recipe ¼ cup sugar ¼ teaspoon salt ¼ cup hot water ¼ cup orange juice plus 2 tablespoons lemon juice 3 ½ cups cold water   In the bottom of a pitcher, dissolve the sugar and salt in the hot water. Add the juice and remaining water, chill. Makes 1 quart or 4 cups. From Nancy Clark’s Sports Nutrition Guidebook, pg. 356.

Sweat drips profusely from your brow, crystallizing into that white salty line on your cheek or neck as temperatures top 90F during the summer months in Portland, OR.

Perhaps you chose to venture out for a walk or run along the waterfront, or go for a bike ride along Marine Drive. Have you ever considered what that sweat soaking your clothes really is, or perhaps even why or how we sweat?

Sweating is a life-saving physiological mechanism used to keep our body temperature stable. Heat is produced by your muscles during exercise, and this heat results in an increased core temperature. Our body transports this heat from our core to our skin, where it can then transfer to the surrounding environment through different mechanisms, including sweat evaporation at the skin surface (Sawka, et al. 2007.)

The amount of sweat we produce can vary depending on a number of factors including (Sawka and Montain 2000; Sawka, et al. 2007:)
• Genetic and individual differences
• Temperature and humidity
• Type, duration, and intensity of exercise
• Acclimatization to weather conditions

As a result of all these different factors, sweat rates can range from 200ml/hour up to over 3L/hour (Sawka, et al. 2007.) Hot summer days can significantly increase sweat rates due to the high heat and humidity, but it is also important to remember, you can lose a significant amount of sweat even in cooler temperatures.

What is this sweat we speak of? Sweat contains water but also electrolytes like sodium, potassium, chloride, magnesium, and calcium. If fluid and electrolyte losses are not sufficiently replaced during exercise, especially longer duration exercise, you will become dehydrated and exercise performance will be negatively affected. You can also experience these negative symptoms if you start to exercise while dehydrated. Therefore, your hydration throughout the day leading up to your workout will also impact your performance.

Symptoms of dehydration may include:
• Muscle cramping
• Physical and mental fatigue
• Increased heart rate
• Headaches
• Dizziness or disorientation
• Less time to fatigue

These symptoms will worsen as fluid and electrolyte losses increase without adequate hydration. In order to avoid this condition, here are some simple strategies you can employ to stay hydrated and keep exercise safe.

Recommendations for Hydration
1. Hydrate before, during and after exercise — Hydrate throughout the day leading up to exercise so you avoid starting exercise dehydrated. Keep a water bottle on hand during the day at work or at home, and include water-rich fruits and vegetables, in addition to other fluid choices like iced tea, natural fruit juices, sport drinks, tea, and coffee. Consuming regular meals will also help replenish electrolytes.

Remember — the old adage “pee clear” is a quick indicator of hydration status. The color of urine can change with certain supplements and medication, but again, this can be a quick indicator to assess your hydration throughout the day.

2. Start early — exercise performance is compromised by dehydration. Current research indicates significant performance effects when fluid losses reach 2% of body weight during exercise (Sawka, et al. 2007.) Starting early and maintaining a consistent intake of fluids during exercise, especially exercise that lasts longer than 60 minutes, will improve performance and help prevent excessive dehydration.

Incorporating electrolyte beverages will help prevent hyponatremia (low sodium concentration in the blood) which may result in overhydration — a condition that can occur from drinking large amounts of water alone.

Also remember, relying on thirst alone may not be effective enough to prevent excessive fluid loss, defined by greater than 2% of body weight (Coyle 2004.) Most individuals, even in situations with unlimited access to fluids, will fall short in attempts to replace fluid losses (Coyle 2004.) Take this into consideration, and start hydrating early and be consistent with your fluid intake during exercise.

3. Include a carbohydrate/electrolyte beverage — For exercise longer than 60 to 90 minutes, using a carbohydrate/electrolyte beverage provides energy, electrolytes, and fluid to keep you going strong. Practice with different products to see what works best for you.