Ernie Kennison had just returned to the dormitory from his usual Sunday morning run and was quietly shaving and showering when I stumbled groggily into the bathroom.

"You look a little tired there, Steve," the muscular 32-year-old laughed as I rubbed my red, aching eyes.

"How far did you go?" I asked.

"Oh, I went about 10," he answered, matter-of-factly, in his distinct Boston accent. "But you're not going to believe this. I ran with a couple of guys who were racing from the Vermont-Massachusetts border to the Connecticut-Massachusetts border. That's more than 70 miles. These guys are crazy."

Crazy? Coming from a man who had just run 10 miles at 6 a.m.? Coming from a guy who was spending the weekend at a triathlon camp?

The East Cost Triathlon Camp featured three grueling days in the hills of western Massachusetts with 22 aspiring triathletes and nine staff members. Three days to run, bicycle and swim to our hearts' content, without once attracting a weird stare or look of incredulity. And, of course, three days to become a world-class triathlete.

Miracles don't happen overnight.

For some, the camp was the first time they had received personalized coaching for the triathlon, the fast-growing sport that combines three endurance events performed one after the other -- swimming, bicycling and running. The longest triathlons may require as much as a six-mile swim, 250-mile bike ride and a 53-mile run. The shorter triathlons may require as little as a 50-meter swim, five-kilometer bike and one-kilometer run.

There are at least 2,000 such events scheduled in the United States this year, compared with just 100 in 1981.

For others, it was a chance to brush up on some of the technical aspects of sport, like swimming stroke length and rate, high-tech bicycle racing parts or efficient and effective running form.

But what united this collection of corporate executives, construction workers, flight attendants and other athletes between the ages of 16 and 55 was one common bond: the rest of the world thinks we're crazy.

To be proficient in three sports requires three times the commitment. Triathletes may train from one hour to eight hours a day, seven days a week, in conditions ranging from 95-degree heat to subzero temperatures. They have the reputation of being hard-core exercise addicts.

Held at Deerfield Academy, a New England prep school, the camp drew participants largely through an ad in the June issue of Triathlon magazine.

Some, like Tod Loofbourrow, came to stay in shape. "After returning from the cross country bike trip toward the end of August," said the 23-year-old computer consultant from Cambridge, "I found it was hard to get in 85 to 100 miles a day riding and I didn't want to lose the shape I was in. So I thought training for the triathlon would be a good way to stay in shape."

For other athletes, like 50-year-old Diane Stuart of West Hartford, Conn., the camp was preparation for a particular competition that represents an elusive goal, the supreme hurdle in life. For Stuart it is the Mt. Everest of triathlons, Hawaii's Ironman, a 2.4-mile swim in the Pacific followed by a 112-mile bicycle ride and a 26.2-mile run held in October. Stuart, who qualified for the 1952 U.S. Olympic swimming trials and has finished the Boston Marathon the last two years, was granted a leave of absence from her job as a reading consultant at the Connecticut Youth Institute in Chesire so she could train.

"I'm a lot older than most of these people," acknowledged Stuart, who was the second oldest camper -- after 55-year-old Ethel Autorino of Valley Cottage, N.Y. "But when I go to these races, I feel a common bond that transcends the difference in the age." Camp started on a Friday night in a small basement classroom. "The whole thrust in this camp," began Hank Lange, the 31-year-old camp director, "is to have you experience this for yourself, to tune you into a little better to your own body."

Lange, who was a coach of the U.S. Olympic ski team in 1984 and competes on the elite Saucony Triathlon Team, then introduced his training approach, called "SMARTER," and his staff, which included Kennison, George Missailidis, Don Cuerdon and Rachel Evans.

Missailidis, a 25-year-old exercise physiologist and fitness coordinator for Aetna Insurance Co. in Hartford and member of the Saucony Triathlon Team, explained the physiology of aerobic training and the meaning of such terms as "VO2 max" (a measure of the capacity to change oxygen into body fuel). The session ended at 11 p.m. as the athletes decided who would do what -- run, bicycle or swim -- at the optional 6 a.m. Saturday workout.

Loofbourrow and I awoke at 6 a.m. Saturday to cycle through seemingly endless miles of cornfields. Some of the other athletes ran or swam, and the smarter ones slept in anticipation of the long, active day yet to come. I tried to take it easy on the bicycle because I was scheduled for the swimming skills session two hours later. Being an awful swimmer, I wasn't looking forward to embarrassing myself in the pool.

Missailidis and Evans greeted about eight of us near the diving area with a video recorder and proceeded to film our swimming form.

"I thought the video was helpful," said Loofbourrow, who, like most triathletes, is least proficient at swimming. "In the water, you really don't see what you're doing. And watching other people swimming wrong helped. Now when I swim, I think about what we were doing wrong and I try to correct it."

Back on dry land, I staggered down the hall and into the wrestling room, which was padded with rubber mats, for a session on sports psychology. Dr. Robert W. Rock and Sarah Pabst Hogenhauer from New York introduced two basic concepts -- relaxation therapy and imagery. At one point, Hogenhauer was doing such a fine job with the relaxation therapy that she put Rock to sleep.

Through use of imagery -- a mental rehearsal of a workout or race -- the two attempted to help Stuart overcome her fear of the occasional heavy winds in the bicycling segment at Ironman. At one point, they had Stuart imagining how helpful, not harmful, the winds would be.

After lunch came a bicycling skills section where we met Don Cuerdon, alias Captain Dondo, a 25-year-old bicycle mechanic and shop manager in Putney, Vt. He led us on a quick ride around Deerfield while he gave us advice on our bicycling form.

Most of our energies at dinner went toward eating, not talking, but the evening was reserved for a session of attitude adjustment -- heavy carbohydrate consumption in the form of Reingold Beer. On Sunday at 6 a.m. the schedule listed an "optional workout for the compulsive exerciser," during which I practiced imagery. I would have pulled off one of the greatest upset victories in the 1986 Boston Marathon if some eager athlete hadn't knocked on my door and awakened me.

I looked forward to the running skills session Sunday morning because running is my strongest event. But 8 a.m. was just too early. We ran quarter-mile intervals, paying close attention to the pulse monitors wrapped around our wrists, and when our pulse had dropped back down to about 125, from as high as 190, we would run another interval. Then Kennison, a member of the Saucony Triathlon Team and a high school track coach at Keene, N.H., filmed each of us running, and we adjourned to the library to watch our form on television.

After brunch, Lange and his staff concluded the camp by reemphasizing some of the main points of the training program and then made themselves available for personal consultations on anything from daily workouts to specific racing tips.

The major criticism of the camp: "I think it was too short," Loofbourrow said. Kennison and Stuart also said they would have stayed even longer. But I have a feeling they'll be back next year. I know I will.