At 4 a.m. on a cool summer morning, 66 men, women and children arise to run four to six miles through hilly, scenic farmland in Mercersburg, Pa. It is a physical test they have prepared for all week with countless rounds of jumping jacks, push-ups, sit-ups.

Sweat.

This is not most people's idea of a good summer vacation.

But for the children, college students, accountants, physicists and car dealers who each paid $195 to attend Kim Studio of Tae Kwon Do's 21st annual summer karate camp, it is a week of wonder.

At the seven-day camp led by Ki Whang Kim, a 9th-degree black belt and instructor with studios in Silver Spring and Rockville, fitness is defined as a healthy body and alert mind. It is achieved through rugged exercise and discipline.

Kim's karate camp is one of hundreds of increasingly-popular fitness camps held each summer across the country. Catering to the fitness-minded of all ages, they offer disciplines ranging from tennis to nutrition. Part of the appeal is the chance to get away from the stresses of everyday life and just concentrate on karate.

"It's a place to eat, sleep and train," said Michael Wolff, 20, a recent psychology graduate of Emory University in Atlanta who is applying to medical school.

"A positive mental attitude is the main point," said Kim, 65, of his training philosophy. "Each student must say 'I can do this,' 'I can wake up and train,' 'I can run eight miles.' If they say they cannot do it, then they never will."

"There is no such concept in our studio as cannot," said Albert Cheeks, a 34-year-old Washington night club manager and fifth-degree black belt in karate. "If it can be done by another human then it can be done, so you must give it your all."

And the students, who range in age from 7 to 56, are expected to give their best performance at all times.

Training consists of three, 90-minute classes a day; two in martial arts instruction and one in a sport such as baseball or soccer.

Classes take place in the gymnasium of Mercersberg Academy, a college prepatory school where the camp has been held each year since 1972. They begin with students lining up according to rank -- black belts first, followed by brown, blue, green, yellow and white. Black belts are responsible for the behavior and well-being of the lower ranked belts.

After a ceremonial bow, Kim, referred to as "Master" or "Sah-bom Nim," Korean for master instructor, lectures on the philosophy of martial arts training.

"Karate is not a sport," he shouts at the rapt faces before him. "It is more mental."

Cheeks, a 20-year student of Kim's, uses the Japanese word bushido, meaning the way of the warrior, to describe the proper mental attitude.

"People misunderstand that term," he says, "because the way of the warrior is the person who respects life and honor, who respects fellow man as a human being. You can cause no harm to him. At the same time, you must stand up for what you believe."

Mental preparation takes place before any physical activity to minimize the risk of injury. "Injuries come from a lack of discipline and mental control and from improper warming up and cooling down," Cheeks said. "People get a little lax and then injuries happen."

Armed with the proper focus and concentration, students begin a half-hour work-out that makes Jane Fonda's "Challenge" video seem mellow. After endless muscle stretches, aerobics (300 jumping jacks, 50 sit-ups, 50 push-ups) and a series of isometric exercises where muscles are tensed for several seconds against other muscles, the body is considered "warmed up" and ready to perform karate.

Katas or forms, a sequence of punches, kicks and blocks acted out against imaginary enemies, are considered the foundation of the martial arts. They utilize all the major elements; proper breathing, concentration, balance, power, and style and are executed with loud, guttural crys.

If your form is meaningless, Kim said, "then karate is nothing."

Next, free-sparring, a controlled fighting situation that is good practice for what might be experienced on the street, is performed. Opponents exchange fast-paced kick and punch combinations as they advance, retreat and dance around each other. Matches last about two-minutes and points are scored by landing light blows to the body.

Aside from the classes, students face several ordeals to test their mental endurance. One is the pre-dawn run. Another is a chilling water meditation where, for 45-minutes, they stand motionless in 65-degree water up to the neck, meditating. For some, this is the greatest challenge.

Barton Hosley, a 21-year-old administrative assistant at Washington's Chronicle of Higher Education, thinks of it as a lesson in patience. "The water is freezing," he says, "and you have to have enough patience and mental control to stay in and not complain."

Kim regards the water meditation as a time to "clean up the mind and body" to restore strength. It illustrates some of the lessons he learned in Korea as a schoolboy from a wealthy family terrorized by less fortunate classmates. He asked himself -- "How can I be strong?" -- and karate was the answer.

For some students, such as Wolff of Potomac, mastering karate is a lifelong dream that began when he saw a karate demonstration in first grade. "I watched some guy do a jump side kick and break a board," he said. "When he hit the board I stood up and said 'That's what I want to do.' "

Working together in the structured camp environment fosters a special kind of closeness among participants.

"When you do something with a lot of people, there is a bond that overcomes racial or any other kind of wall that people have," said Marcella Byrd, a 23-year-old third-degree black belt who has been studying karate since she was 14.

"Camp is really a love-hate relationship," said Barton Hosley. "It is something that while you're doing it, you hate it, but at the end you feel fantastic about it because there is that camaraderie."

But many could argue there are less strenous ways to stay in shape and be healthy.

"If you want just a physical fitness camp, go to a weight-training or aerobics camp," said Cheeks. "For myself, the martial arts has given me a great respect for life itself. But that can only be given if the correct mental discipline is there and the philosophy to back it up. Otherwise, you have an empty art."