The previous morning, Diglio, a 41-year-old attorney from Garden City, had left her two children with her ex-husband and driven upstate to Lake Placid to compete in the Ironman USA triathlon. The night before the race, she was beset by the usual doubts of anyone attempting a 2.4-mile swim, 112-mile bike and 26.2- mile run. Could she go the distance? Had she done everything she needed to? Was she crazy to even attempt this?

Lucky for her, there was someone around to quiet her anxieties: her friend and training partner, Caroline Barry from Port Washington. They had met in early 2004 while training for a shorter-distance triathlon and developed a close friendship. Barry, also a 41-year-old single, working mom, had come to Lake Placid not to race but to be Diglio’s support crew, cheerleader, confidante.

“She was such a calming influence, like a rock, steady and supportive,” Diglio recalled. “Any doubts I had, she was always there ready to encourage me.”

“I’d gone through it myself,” said Barry, a teacher’s aide who had completed her first Ironman in 2004, in Florida. “So I sort of knew what someone needed to have done for them. It was great to give back.”

On the morning of the race, Barry rose with Diglio at 4:30 a.m. and accompanied her to the start on nearby Mirror Lake. She then stayed on the course for most of the 15 hours, 20 minutes and 30 seconds it took Diglio to complete the Ironman, hooting and hollering every time her friend passed by on bike or foot. And when Diglio finished, Barry was there, as well, to offer a well-deserved hug.

“She really took care of me,” Diglio said. “As you get older, it’s hard to make friends. I just consider myself so lucky I was able to find her.”

Whether your goal is to finish a triathlon or a walk around the block, finding a friend can be a critical step in sticking with an exercise or weight loss program.

“It is absolutely necessary to have some support and motivation like this to be successful,” said psychologist Dr. Howard Rankin, author of “The TOPS Way to Weight Loss” (Hay House, 2004). That support, Rankin added, doesn’t have to come from a formal support group; small groups or individual friends can also provide it.

“Social support is a very, very powerful force,” agreed sport psychologist Dr. John Murray of Palm Beach, Fla. “There is an enormous benefit in having the teamwork, the shared goals, the positive motivation from others.”

After years of false starts in exercise, long-time friends Kim Murphy and Kris Carpenter of Vienna, Va., decided to test this theory: The two trained together with the goal of completing a half-marathon (13.1 miles) foot race in Virginia Beach.

“After finishing the half, we were so struck by the fact that we had finally succeeded at exercising consistently,” Murphy said. “We realized that if it could work for us … the concept of having a friend as the partner, … it could work for others, as well.”

So Murphy and Carpenter wrote a book, “The Best Friends Guide to Getting Fit” (Capital Books, 2005). In it, they offer no new weight loss “secrets” or “revolutionary” workout programs; rather, they assert a basic truth that, depending on your point of view toward exercise, can either be described as “misery loves company” or something slightly more ennobling.

“We believe in the power of friendship,” the women write. “Having a friend helps curb waning desires and motivation. It gives you a reason to go. The friendship seduces you into being consistent [in your training].”

It’s a sensible idea, and yet one that stands in stark contrast to the still-common notion of exercise as a hardship that must be endured alone, a solitary battle in which you wage “war” against your waistline, your sedentary habits or simply the progression of time. It’s true that some people prefer to train alone, but if you have gone the solo exercise route and failed, maybe it’s time to try with a little help from your friends. Indeed, it may change your whole attitude toward the pursuit of fitness.

“You go to your workout because you want to see your friend, have some fun and a few laughs, and you’re looking forward to having a great conversation,” Murphy said. “It nurtures your soul.”

Certainly, that’s been the case for training soul mates Diglio and Barry, who plan to compete in the 2006 Ironman triathlon. This time, however, they’re going to do it together.

“That’s what really makes it exciting,” Barry said. And, in some ways, more doable: The two are already discussing how to best maximize their time – such as bringing together their four kids and a baby-sitter while they do long training rides or runs. And on race day in July, they’ll stick close together again in Lake Placid, this time helping each other meet their long-distance fitness challenge.

“It’s not a competition with us,” Barry said. “It’s a partnership.”

How to pick the right workout buddy

Experts agree that the social support of a good training partner can increase the likelihood of reaching your exercise goals. Here are some tips on how to find the right friend for fitness:

Choose someone who is good company: “Because you will spend large chunks of time with this person, be sure it’s someone you can be completely yourself with,” say Kris Carpenter and Kim Murphy, co-authors of “The Best Friends Guide to Getting Fit” (Capital Books). “Pick someone you trust … a friend you can laugh with … a person you can rely on.”

Choose someone on the level – your level: Hooking up for a run with that friend of yours who has done 10 marathons, or weight-lifting with the buddy who can already bench-press 300 pounds may only work if you’re equally accomplished. “You have to be careful to choose someone who is at your level,” said sport psychologist Dr. John Murray of Palm Beach, Fla., “or the difference in reps, laps or time will bore the more advanced one and overwhelm the less advanced.”

Choose someone who can relate: A successful training partnership doesn’t have to be between people of the same age or station in life, but it sure helps, as Caroline Barry and Maria Diglio – local Ironman triathletes and training partners who are both 41-year-old single moms – can attest to. “A lot of our friends do the Ironman,” Barry said, “but having a friend who is in the same boat as me is really helpful. She understands.”

Choose someone close to you (in more ways than one): “The best place to look for a training partner is amongst friends who are trying to do the same thing,” said psychologist Dr. Howard Rankin. “With friends you already have the necessary bonds in place for effective communication and support.” But that closeness also means proximity – the likelihood of training consistently with a friend who lives down the block is greater than with the one who lives an hour’s drive away.

Can’t find a friend to exercise with? Visit www.exercise friends.com, a free Web service that matches up members with local people of similar fitness goals and abilities. (The Web site currently has about 10,000 members from the metropolitan area).