I’m obsessed with fluids this week! I’ve spent the last week becoming acclimated to South Carolina workouts during our vacation from the cooler, less humid Midwest. Some of my symptoms have included profuse sweating, even my forearms were drenched! My heart rate went up during my long runs. At 1% dehydration (1% of body weight or 1.5 pounds for 150 pound person) your heart rate increases 3-5 beats/minute. My endurance and speed took a nose dive. At 2% dehydration level exercise performance, cognitive and mental impairment set in. Fortunately, I ran with sports drinks, never stopped sweating, got chills or cramps, signs of severe dehydration. I also never experience the drunken sailor run or watched the pavement move at a different rate than the horizon. My sweat was a good sign and got better as the week went on and here’s the science behind it.
Whether you run, bike, or swim, sweating is a good sign. Your body is two-thirds, muscle is 75 percent and blood is 95 percent fluid. Sweating signals that you’ve properly hydrated these key areas so that you can perform at your best. When you exercise, the muscles that perform the work create internal heat and this heat is released from the body in the form of sweat. In the absence of sweat your body temperature rises, you to become overheated, and your body’s ability to function plummets.
Dehydration is the #1 cause of fatigue during exercise and it can happen very quickly in the absence of adequate fluid intake. The rules of proper hydration are:
- 2 cups fluid 2 hours prior to your workout
- 1-2 cups fluid 15 minutes prior to your workout
- 6-12 ounces fluid every 15-20 minutes during
- 2 cups fluid per pound lost following
Sweat rates for individuals vary based on the activity, temperature, humidity, body weight, genetics, acclimatization and metabolic efficiency. While some of these sweat factors are out of your control, don’t underestimate the value of proper training. Untrained muscles create more heat in the attempt to perform the new activity. As they adapt through regular workouts, less sweat is created. However, remember that if you increase your time, intensity or length of training, your sweat rate will rise.
According to the American of Sports Medicine, the average amount of sodium lost in sweat is 1 gram/Liter (50 mmol/L) although concentrations vary widely. Modest amounts of potassium, and small amounts of magnesium and chloride are also lost in sweat. Water is the fluid of choice in events lasting less than one hour, but switch to sports drinks for longer activities or during high heat, high humidity workouts. Sports beverages contain sodium and potassium to replace electrolyte losses, stimulate thirst and fluid retention and carbohydrates for continued energy.
For more information on sweat rates and dehydration check out my previous posts:
Categories: Sports Nutrition