Triathletes, on your mark, get set … Whoa!

 Rick Motter remembers the first twinge.

 He was about to finish first in his age group at the Reeds Lake Triathlon in East Grand Rapids, Michigan, when, after swimming 805 meters and biking 28 kilometers, a younger competitor began to surge by him at the end of the 8-kilometer running portion of the race.

 “I thought, ‘Well, that’s not going to happen,’ and I sprinted really hard — that’s when I felt it,” said Motter, 61, a manufacturing plant manager from Plainwell, Michigan, who began competing in triathlons three years ago when his doctor told him he needed to reduce his cholesterol.

 Soon the twinge in his right ankle evolved into severe pain, severe enough that he wound up in physical therapy with Achilles tendinitis. “A lot of my triathletes end up here because they do way too much too soon,” said Scott Miller, Motter’s physical therapist.

 As more casual athletes like Motter sign up for triathlons, the sport has seen a corresponding rise in injuries. The newcomers are particularly injury-prone, doctors say, because of the rigors of training simultaneously for swimming, bicycling and running.

 Paradoxically, many people move from a single sport to triathlons because of the oft-heard promise that adding variety to their exercise regimen will reduce injuries. The theory is that the three sports work different muscles, ideally minimizing the strain on any single muscle set. For runners in particular, adding biking and swimming to their repertory means less pounding against pavement.

 But in practice, people who take up triathlons tend to train harder, adding rigors to their workouts without necessarily subtracting anything. Thus, the idea that people can reduce their chance of injury by competing in triathlons may be a fallacy.

 “That’s been a throwaway line for quite a long time,” said Dr. Joshua Burns, a researcher and podiatrist at the University of Sydney in Australia, who has studied the nature of triathletes’ injuries. “As humans, we try to do as much as we can to be the best we can,” he said. “So if we’re just running and doing 10 hours of workouts a week and we switch to triathlons, now we’ll try to work out 20 hours a week. It’s like a bottomless cup. You can’t do enough, and people end up breaking down.”

 His study of 131 triathletes in Sydney found the same basic result that other studies have over the years: that triathletes suffer as many injuries, if not more, than people who just run — and certainly more injuries than people who just swim or bike.

 “What we have to compare it to other sports is the injury rate, and triathletes have one of the highest incidence rates of any sport,” Burns said. “So there is a compound effect” of doing all three activities in triathlons.

 The health news for triathletes isn’t all bad. Most of the dozen doctors, physical therapists, coaches and athletes interviewed for this article said they had seen fewer triathlon-related injuries than injuries related to other sports. But they also said that newer triathletes suffered more injuries than more experienced ones.

 Mike Walther, 32, a computer engineer in Pittsburgh, Pennsylvania, who has competed in triathlons for two years, had an accident during bicycle training and is recovering from a broken collarbone. (It’s an injury that one physical therapist called “a triathlete’s rite of passage” because of how common it is among newcomers.)

 Walther had been a competitive swimmer and a recreational cyclist before a friend persuaded him to begin running, which led him to triathlons. “I don’t look at my shoulder injury as related to my triathlon training,” he said. “It could have happened on a Saturday recreational bike ride. My friends with more experience in triathlons tell me I’m lucky to have suffered the injury so early in my career, because I’m just starting out and haven’t been set back much.”

 Even the most experienced triathletes are not immune to injury. Paula Newby-Fraser, 47, who has won the Ironman World Championships in Hawaii eight times, was at her peak in 1993 when, she said, she decided to increase her training. It was then she sustained a stress fracture in a foot.

 “I thought, ‘If this much gets me through, then that much more will get this,’ ” she said, ” ‘If riding 100 miles a week was good, then 200 miles a week will make me that much faster.’ “

 Newby-Fraser has a name for this mind-set. “I call it athletic greediness, and that’s what a lot of new athletes coming in to it do and get injured,” she said.

 Doctors, therapists and coaches say the most common injuries among triathletes come from overtraining, usually in the legs from running and cycling. Typical problems are stress fractures, injuries to the Achilles tendons and knees, and iliotibial band syndrome, which causes pain in the thigh or knee region. But doctors also see plenty of swimming-related injuries: many a new triathlete has overtrained in the pool and hurt a shoulder’s rotator cuff.

 Triathletes are prone to “everything that a swimmer, runner or cyclist gets,” said Dr. Andrew Hunt, medical director for USA Triathlon.

 Doctors and coaches point out that the sport is still new, and there is still time for it to live up to its cross-training purpose. The first modern triathlon was held in 1974, and the Ironman competition began in 1978. The recent surge in popularity has put the sports medicine community on a fast learning curve as it tries to address the injury problem.

 One lesson — that less is more — has come through loud and clear. At the coaching certification clinics run by USA Triathlon, instructors drive home the point that while there are benefits to doing 10 to 12 workouts a week, maybe triathletes don’t need to run as far some days, that a day off is more than good for the soul, and that putting more time on the bike and in the pool can make up for one day fewer spent running.

 “You don’t build your fitness while in a workout, you build while in rest mode,” said Mary Delaney, a physical therapist, triathlete and certified coach. “As your whole self and cardiac system need to recover, you’ve also got to let your muscles and tendons recover, too.”

 Motter, the triathlete in Michigan, said his Achilles tendinitis was a result of overtraining and not stretching properly, according to his doctors. He said that working with a physical therapist, modifying his workouts and stretching more over the last year have helped.

 Yet, in typical triathlete fashion, he has never really stopped exercising to recover. “I have a hard time taking off,” he said. “I just enjoy the effort and activity so much, and right now the pain has been bearable.”