In my first triathlon about 15 years ago, I was in a huddle of wet-suited men about to wade into a lake in Maryland when an acquaintance next to me offered a singularly useful piece of information.

He said it was common for people to have panic attacks in the swim leg of triathlons, which are races that consist of swimming, cycling and running various distances, in that order. He’d done a few. We knew each other from training three mornings a week in a bright, clear Olympic-size pool.

“You’ll see. Within the first hundred yards or so, a couple people will swim right to the shore. They’ll be freaked out. The race will be over for them.”

In a minute, we were standing in water so dark you couldn’t see anything a foot below the surface. The bottom was squishy underfoot. It was not yet 8 o’clock in the morning. The wet suit, which I’d put on only a few times before, was tight around my chest and cold as the water seeped in.

The starting horn screeched.

Fifty or 60 of us, all wearing identical swim caps whose color denoted the age and sex of our starting group, began to swim. We collided and had our faces bumped and kicked as we made our way into open water. Within a few minutes my heart was racing, I was breathing fast and I was scared to death, although I wasn’t exactly sure why.

I rolled onto my back to calm down and let the pack move on. As I sculled slowly, I looked to the shore. Two men were climbing out on all fours.

Something in the water?

I think of that day each time I hear that someone has died in a triathlon.

This past summer, at least nine people in the United States died, a number that appears to be a record in a sport experiencing a boom similar to what occurred with running in the 1970s. More than 243,000 people competed in 2,500 triathlons in 2010. USA Triathlon, an organization of competitors, race directors and coaches, has 150,000 members; in 2000 it had 21,300.

Whether nine is a complete count of fatalities isn’t known. USA Triathlon, which keeps track of deaths in the 2,500 races it sanctions, won’t provide the numbers. It has, however, recently appointed a panel of three physicians and two race directors to look into them.

All but one of the nine deaths occurred in the swim portion of the races. The one exception was a 59-year-old Arlington man, John Park, who collapsed shortly after starting the bike event in the Nation’s Triathlon, which was held in the District on Sept. 11. A similar preponderance was seen in the only rigorous analysis of triathlon deaths, which appeared last year in the Journal of the American Medical Association. Researchers at the University of Minnesota found 14 deaths from 2006 through 2008. Thirteen occurred in the water.

In most of those cases, as in this year’s, drowning was the official cause of death. In about half, some minor heart abnormality was found and cited as a possible contributor. The most common was thickening of the heart muscle, which can be a normal consequence of training, and atherosclerosis, which is present in virtually all adults.

Damaged heart tissue — evidence of a myocardial infarction, or heart attack — has never been found in these cases, nor have any of the rare molecular defects of heart muscle occasionally associated with drowning. Nevertheless, news reports usually give “cardiac arrest” as the inciting event, leaving the impression they’re the consequence of heart disease.

In all, an air of fatalism and mystery surrounds these tragedies. But are they mysterious and unavoidable?

I don’t think so.

My hypothesis is these athletes suffer panic attacks, a state characterized by a racing heart, sensation of breathlessness or choking, and a feeling of lost control.

In the swim event, a combination of stresses can lead to a panic attack (or something like it): the excitement of the moment, the chaos of swimming into and over other people, the chest constriction of the wet suit, the darkness and coldness of the water, competitiveness and the desire not to quit when friends and family are watching. On rare occasions this leads to drowning.

Discussion threads on blogs suggest that panic attacks are common even among experienced athletes, although apparently nobody in the triathlon industry has attempted to learn how common they are. Some coaches mention them, but many triathletes train without coaches. Race directors in general don’t name panic attacks as potentially lethal but manageable hazards, though they do warn about wet roads for cyclists and high temperatures for runners.

Perhaps the biggest problem is that panic attacks leave no trace, making it hard to make them a contributing cause of death.

“My world is anatomic,” said Steven Shapiro, Vermont’s chief medical examiner, whose office investigated the deaths of two men this year. “I can’t point to the body and say: ‘There’s the panic attack, there’s the arrhythmia.’ Once you’re in my office, there’s no panic and the rhythm is asystole,” he said, using the medical term for cardiac standstill.

Nevertheless, circumstantial evidence strongly points to panic, with the biggest piece of evidence the most obvious. Something is happening in the swim that isn’t happening on the bike or run.

“I was taken by surprise the very first time I did a triathlon,” said James A. Millward, a 50-year-old history professor at Georgetown University. “I swam about 50 yards, I couldn’t get into a breathing rhythm, I felt more and more anxious, and I thought, ‘Wow, I’m having a panic attack.’ ”

Millward has done the Nation’s Triathlon four times and has had the sensation each time after jumping into the Potomac River with scores of other racers. The overwhelming urge is to get his head out of the water. One year he practiced the start and swam half the course the day before, hoping that would get it out of his system.

“Interestingly, I had no problem then. But I was surprised the next day that under race circumstances it came up. I’ve come very, very close to bailing out each time,” he said.

It’s impossible to know what the experience of this year’s victims was. But a look at them sketches a picture of people who were inexperienced with triathlon and open-water swimming, had in some cases expressed worry and in some cases had heart abnormalities of uncertain significance.

‘In phenomenal shape’

Michael Paul Wiggins, a 42-year-old physician from Fort Collins, Colo., died on May 28 in the Pelican Fest Triathlon in Windsor, Colo., an event that started with a half-mile swim in 61-degree water. It was his sixth race.

“He expressed a sense of anxiety about having to do the swim portion,” his widow, Jacqueline Wiggins, said recently. But, she said, he had a plan.

“He would just roll over, calm himself down and rest a bit on his back and then continue on with his swim,” she said. “He did that last year in the same race.” Wiggins wore a wet suit and was found floating about two-thirds of the way through the swim.

His widow also said he had had three episodes of atrial fibrillation in the previous four years. He was taking two drugs, flecainide and atenolol, for the abnormal heart rhythm.

Five days before his death, Jacqueline Wiggins reported, his cardiologist had told him: “You’re in phenomenal shape; your heart is strong; there’s no indication for you to continue on this medicine anymore.” The plan was to stop it the day after the race.

Death in the Hudson

In August, two people were fatally stricken while swimming in the New York City Triathlon, the same race in which a 32-year-old man drowned three years ago.

One of this year’s victims was Michael Kudryk, a 64-year-old New Jersey man; his survivors could not be reached by The Post. The other was 40-year-old Amy Martich, an investment analyst and mother of three from a Chicago suburb. She was pulled unconscious from the water and died the next day.

The swim was almost a mile in the Hudson River along the seawall on Manhattan’s West Side. Martich had swum in high school and had worked as a lifeguard. Her father, Fred McCullough, said she’d done one triathlon previously.

An autopsy found that Martich had mitral valve prolapse — floppiness of a valve on the left side of the heart. Researchers have debated for decades how common and significant this abnormality is. The pathologist concluded that the condition was responsible for a “cardiac arrhythmia” that caused her death.

“The way they explained it to us, that’s a conclusion you come to when they test for everything and they don’t find anything,” her father said.

The medical examiner’s office declined a request to talk to the pathologist who did the autopsy.

Afraid of water

Mark Wezka, a 46-year-old computer specialist from outside Buffalo, died Aug. 28, less than 10 minutes into the Ironman Louisville triathlon, which begins with a 2.4-mile swim in the Ohio River.

Wezka was extremely well trained and thought nothing of going for a 90-mile bike ride on a weekend, said his father, Anthony J. Wezka. He swam three times a week at a YMCA. But the Louisville race was his first triathlon and his first swim in open water.

“He was worried about the swim just because he did feel he was prepared but he’s always been afraid of water,” his sister, Sue Richardson, told a local television station. Richardson, who had come to the race to watch her brother, said he was also taking medicine for high blood pressure.

Jo-Ann Farmer, the coroner who did the autopsy, said the cause of death was drowning complicated by “hypertensive cardiovascular disease.” She said Wezka’s heart was mildly enlarged.

Two cases in Vermont

Christopher Ludington, 57, of Morrisville, Vt., regularly rode eight miles over hills to his job. On Memorial Day weekend, he ran a half-marathon in Burlington. On June 16, he drowned in a lake during a triathlon near Stowe.

It was his fourth triathlon but only the second one in open water. His 25-year-old son was in the same race and later said that for most of the course the water was shallow enough to stand up in.

Ludington’s widow, Susan, blames his death partly on a wet suit he’d just gotten.

“He was terribly claustrophobic. . . . It was really tight. My hypothesis is that he was swimming and it was so tight that his chest couldn’t expand, and he panicked.” She added that “the swim was the part he was most anxious about.”

Vermont’s medical examiner ruled the death a “drowning in setting of presumed cardiac event.” At autopsy Ludington had “dilated cardiomyopathy,” an enlargement of the heart that can increase the risk of sudden death. It also found “atherosclerotic cardiovascular disease,” which is found in 85 percent of people over 50.

A second Vermont man, 42-year-old Stephen J. J. Mount, drowned two weeks later in a different triathlon. A mild thickening of the heart muscle wall — the most common finding in athlete deaths — was seen at his autopsy.

‘Naturally anxious’

David A. Aschauer, a 58-year-old professor of economics at Bates College in Maine, died on Aug. 22, a day after being pulled unconscious from the ocean off Cape Elizabeth, near Portland, in a triathlon.

“He was a very healthy man. His father lived to 96. I don’t think he just went out there and had a heart attack. He ran and biked. But this was his first triathlon, and I’m sure he had no idea what it was like,” said his former wife, Sarah Aschauer.

Although he had done numerous sessions in open water, “I’m sure he was definitely nervous about the swim that day,” said his daughter, Erika Rodrigue, who was doing a triathlon in New Hampshire the same day. “He had a naturally anxious personality.”

She said he thought that if he didn’t finish in the top one-third of his age group he would be embarrassed.

“He was very driven. He could have been pushing himself past his own point of comfort.” The death, tentatively ruled a drowning, is still under investigation.

Another man, Steven J. Linthicum, 46, of Westminster, Md., died on Sept. 18, a day after he was pulled from the water at the Dewey Beach Sprint Triathlon in Delaware. His death is also still under investigation, and his wife did not want to talk.

Addressing the issues

“I think almost every triathlete that’s being honest has had these feelings. It just depends on the person whether you call it panic or not,” said Jack Caress, a 57-year-old race organizer who is president of Triathlon America, the industry’s trade organization.

He added: “I think these issues need to be much more honestly addressed. Sadly, because of what’s happened this year, it’s brought it more to the forefront.”

Successfully addressing the problem may be difficult. The New York City Triathlon, which has had the most deaths, has been trying to help participants cope with anxiety for a while.

About eight years ago, the race organizer, John Korff, wondered why at least 40 people a year got to the starting line but never started.

“I called them and by talking to a bunch I pieced together what was happening,” Korff recalled recently. “These people were in a state of distress, anxiety, some kind of panickiness. But most people — even New Yorkers who are free to say what their shrinks cost — don’t want to say, ‘Hey, I had a panic attack.’ ”

The race now mentions panic attacks and advises how to cope with them in a pre-race meeting required of all competitors. There is a drop-in “Psych Tent” on the route to the swim start. A team of psychologists roams among the waiting competitors, and another psychologist is stationed on the dock from which people start.

“You could sort of see it in their faces or their body language,” said Stacy Rosenfeld, a clinical psychologist and triathlete who ran the program from 2007 through 2010. “They were often standing off to the side. You’d just see that empty stare. Or they would come up and ask an anxious procedural question.”

The strategy was to help them understand that they were well trained and that they could do things (such as swim at the edge of the pack near the rescue boats or float on their back) if they panicked. They were allowed to start when they felt ready, even if that meant missing their assigned group.

“We never say, ‘Hey, man up, you can do this,’” Rosenfeld said. “If in the end they aren’t comfortable, we respect that.”

The number of no-starts is now fewer than 10 out of 5,600 competitors.

Perhaps only New York could be expected to provide real-time cognitive behavioral therapy by a roving band of shrinks. Nevertheless, the whole sport can probably do a better job of trying to prevent these rare and tragic deaths.