“No sweat, no glory.”

“Sweat is fat crying.”

“Good things come to those who sweat.”

These are popular mottos among the fitness set. But is there any truth to them? Is sweat really a sign of fitness? Do athletes sweat more?

Yes, so embrace it.

“Sweating is one of the best methods of cooling the body,” says Max Prokopy, director of the University of Virginia SPEED Clinic.

Sweat is a byproduct when the body heats up to convert chemical (glucose) energy to work (muscle) energy, Prokopy says. Sweat helps keep the body temperature between 98 and 103 degrees Fahrenheit no matter how intense the workout.

“Performance really starts to suffer at 103,” he says. And if you reach 104 degrees you are risking heat exhaustion or worse.

Everyone sweats when exercising, but when and how much can vary widely, says Julieann Harris, an American College of Sports Medicine-certified personal trainer in Frederick.

“Athletes tend to sweat sooner and more,” she says, explaining that active people convert chemical energy to work energy faster and that their bodies are conditioned to sweat sooner, at lower temperatures and in anticipation of what’s coming (a long and/or hard workout).

In the end, this allows athletes to go harder and farther without causing the increased body heat that could hamper performance (or worse).

In other words, sweating is a form of conditioning — an adaptation — that allows us to keep going. Humans — among mammals — are pretty good at this particular adaptation.

“You can train your body to sweat more as you increase intensity and duration over time,” Harris says.

But copious sweating comes at a cost. You have to replenish the water and sometimes also the other “waste” products, such as salt.

Prokopy says water usually does the trick, but if electrolytes are called for, he recommends cutting orange juice with water (50/50) and adding a pinch of sea salt to the mix. He recommends 20 ounces of liquid for every 45-60 minutes of moderate to intense exercise.

Harris says that after 90 minutes you might need to add some sugar (carbohydrates) to the water and electrolytes. Some athletes weigh themselves before and after training to see how much fluid they need to replenish.

Mike Hamberger, a D.C. running coach, says it’s important to remember that short, intense workouts can cause just as much sweating as a long, less intense workout. “I always have to remind runners to hydrate when we have our 30-minute track workouts,” he says.

Prokopy notes that the short and intense workouts where the heart rate is in the anaerobic zone (80-90 percent of max heart rate) usually don’t produce all that much sweat until after the workout is finished and your body is recovering.

Other ways to help the body stay cool in Washington’s hot, humid summers include removing makeup to unclog pores, wearing wick-away shorts and sleeveless tops to allow sweat to evaporate, arranging your hair short or in a ponytail (off the neck) and slowing down your pace and intensity a bit.

“I call training in the summer in D.C. ‘mock altitude training,’ ” says Hamberger, adding that “heat training” is a way to increase your blood plasma volume. This in turn leads to higher fitness levels. “Come mid-September, you’ll feel great,” he adds.

The amount of sweat we produce varies from person to person. Obese people, for example, tend to sweat more because of thicker layers of fat that insulate the body.

Women have as many or more sweat glands than men — a few million — but men tend to sweat more, Harris says. “This has to do with the fact that men have more muscle mass, create more waste product and have more overall body mass.”

One interesting thing in terms of gender differences, says Prokopy, is that prepubescent boys and girls have the same sweat rate. It’s only after puberty that boys start to sweat more. “There seems to be a testosterone component.”

Think you sweat more than most people? It could be a genetic predisposition, or if it’s really bad, you could be among the 3 percent of people for whom excessive sweat is a medical condition (check with a doctor).

But for most of us, sweating during exercise is perfectly natural — and very good.

Boston is a fitness trainer and freelance writer. She can be found at www.gabriellaboston.com.