So when the world-renowned physical therapist crossed the line at Kona on Hawaii's Big Island 10 days ago having completed the daunting 140.6-mile event in 11 hours seven minutes and 24 seconds, the 42-year-old was not just finishing one of the toughest sporting tests of human endurance, he was closing a chapter of his life that had been left open since a very dark day in 1991.
He may now have a client list at his hometown Limerick practice including such luminaries of the track as Paula Radcliffe and Sonia O'Sullivan and 30 other Olympic medallists but when disaster struck
Hartmann on a training ride along a Florida highway 12 years ago he was in his seventh year as Irish Triathlon champion having finished as high as 14th in the World Championships and sixth in the Europeans.
He had also competed in the famous Ironman event on Hawaii, a gruelling race involving a 2.4 mile ocean swim in Kailua Bay and a 112-mile cycle road race finished off with a marathon run over 26.2 miles.
Following his accident, however, Hartmann had thrown all his energy into his developing physiotherapy career, and blotted out all thoughts of the triathlon and its components.
Until, that is, he got a call from Cyle Sage, the US national triathlon team coach and an old friend, who told the Irishman that he had been invited back to Hawaii.
Hartmann said: "Cyle told me all about the 25th anniversary Ironman and how it would be a very historic day. Initially I said 'No way'.
"But it was always at the back of my mind and deep in my heart that one day I would go back to that island. I just didn't know when.
"It's a very spiritual event and there are deeper issues. There's stuff that goes on there it's like, you're out there on a lava field and it was 105 degrees there at one stage during the race last week and you're just not sure what's going to happen.
"I've been to a lot of different events all over the world and this one is very, very unique.
"You're up against the elements and you're up against, I don't know, this energy that's out there and you have to call upon an awful lot of your deeper thoughts while you're out there. And a lot of stuff comes out."
Having decided to compete, and having told his illustrious clients they would be seeing a lot less of him between April and November, Hartmann turned his attentions inwards for some 'me time'.
He had spent that period wisely; in fact, his preparations including a mandatory, qualifying half-triathlon, his first event in 12 years, which he completed in England had gone great, until the week of the big race itself.
And of all the problems that could hinder him, it was one involving his nemesis, the bicycle.
"I was very blasé about the Ironman when I went out there the first time. I had a bike that was so antiquated it would make you laugh and I was very naïve.
"This time round, when the invite came, it was a chance to go back and close a chapter. This was about my career suddenly being shot at 31 years of age. And it happened so quickly that I turned my back on it, I didn't want to deal with it.
"A lot of my friends were in triathlon and I turned my back on them, I didn't have time for them anymore, I didn't want to go near the triathlon.
"The first time I got back on a bike (after the accident) was after seven years, in 1998. It was very difficult for me, I felt that every second I was on the bike that a car was going to hit me. So I had to overcome a very big fear factor because when I went down that time I went down very hard."
SO IMAGINE what was going through Hartmann's mind when, a week before the race, he was going downhill on a training ride in Hawaii when the bike went into a major speed wobble.
"It was as if someone was shaking the bike violently," he said. "I took it to a bike shop, they took a look at it and couldn't see anything wrong with it. So I took it to another bike shop and still they couldn't see what was wrong with it.
"So that was fine, but coming up to Ironman you don't want to be changing your plans just before the event and it felt like my bike had deserted me and all my confidence in it had gone."
Standard practice for athletes in the build-up to an event such as this is to wind down preparations around 48 hours before start time and take things easy.
Hartmann had wanted to follow that routine but, despite the experts' clean bill of health for his bike, doubts about it kept nagging away.
He knew there was something wrong with the bike and he didn't want to have it proved to him halfway through the 25th Ironman as he descended a hill travelling at nearly 50mph with a tailwind.
"I wanted to ride it again just to make sure. So on the Thursday, two days before the race, I drove out about 20 miles into the middle of the lava field where there's a very fast downhill straight.
"I decided to go down this thing at 45 miles per hour and get this thing out of my system. So I went down the hill but I had to pull up because the bike, for some reason, just wasn't right."
Hartmann's instincts hadn't deserted him. Just minutes after he had pulled out of his high-speed test and at a far gentler pace, his cycle frame split in two.
"My bike was in two pieces and it was two days before the race. The bike shops had missed it because it must have been a hairline crack under the paint work.
But if I hadn't gone for that test ride it would have given out during the bike part of the race and I would have suffered a serious injury."
That was the good news. The bad news was that with two days to go to the big race, Hartmann didn't have a bike. Despondency had set in and he was considering withdrawing from the event when he visited the trade fair at the Ironman venue.
He went to see a friend on one of the stands at the Expo and while he was there the fates turned in his direction.
Opposite him was the Cannondale stand, the official bike sponsors of the Ironman. And not only did they offer him a helping hand, they loaned him their last remaining prototype of the Cannondale 2004 Ironman 5000 bike.
The only problem was that the frame was the wrong size, not by much, but enough for Hartmann to contemplate withdrawing.
At this level of competition, bikes are set up very specifically for the individual riding them. They become an extension of the athlete, an amalgam of cycle and sinew, fused together by mile after mile of training on the road. You can't just hop off one and climb onto another and expect the transition to be seamless.
Hartmann's borrowed, whiz-bang Cannondale of the future had a 60cm frame and that could have serious consequences for a set of muscles so finely attuned to his normal spec bike, with a frame two centimetres smaller and a different geometry. Riding that would be like a runner with size 10 feet racing in size 6s.
So on the Thursday evening before the race, he was left with a stark choice: withdraw from the race and walk away from a year's preparation for an extraordinary event or go to the start line, ride a strange bike and risk the strong possibility of his muscles seizing up half way through.
By Friday afternoon he was back in the lava field, test-riding his newly acquired Cannondale hurtling along the Queen Kaahumanu Highway when he should have been restricting himself to very light training. Hartmann would go to the start line the following day.
"This wasn't about the race," he said, "this was about my myself and the course. I think this was about finding stuff and closing a chapter for me.
"I'm not in the sport of triathlon anymore; I don't consider myself a triathlete anymore. But I needed to close the chapter and I need to go back, not just to any triathlon, but back to Hawaii for the Ironman and all that was happening there in terms of the energy. For me it was a very powerful day."
Inevitably, the 112-mile bike section of the race caused the most discomfort, eventually.
"The accident of the bike cracking was unfortunate but having had to get on a different bike, I didn't think about it until about 25 miles into the bike ride. It wasn't until then that I started to feel sore.
"I had to stop three times on that section because 112 miles is not the sort of distance to take out a bike for the first time. So I had to call on a lot of past experience to get through that.
"Having worked with someone like Paula Radcliffe, for example, she draws upon a huge reservoir of psychological and emotional strength.
"And all I kept saying to myself during the event was 'okay, get off and stretch for two minutes. The day will end. It doesn't matter if it takes 17 hours to do this event, forget that you're a competitive athlete, to finish is to win and to win is to finish'.
"I kept saying that to myself, over and over. I kept saying 'I can't go back; I'm here to finish this sucker. That's what I came for, I didn't come for a 10- hour or a nine-hour race time; I didn't tune in to what anyone else was doing. It was just myself and the event and on that day I drew upon more mental strength than physical."
Hartmann came back from Kailua-Kona not just with closure having completed the Ironman against all the odds and closing a traumatic chapter in his life. He also returned with fresh challenges.
FOR NOW, with the Olympics only months away, he will throw himself back into his work as his clients prepare in earnest for Athens. But once those Games are over, the physical therapist is determined to get back on his bike.
"There's one other thing I want to do and it won't be next year because of the Olympics and the next nine months will be absorbed with giving my time to these athletes. But I want to cycle from Mizen to Malin.
"The plan is to go from Mizen to Limerick, which is about 145 to 150 miles, grab an hour's stop and then go from Limerick to Sligo, which is 144 miles, and then Sligo to Malin. It'll take somewhere between 23 and 27 hours but it'll be in one shot.
"Whether I end up doing it for charity or fund-raising or whatever I don't know but that's my plan for after the Olympics. I won't say I'm going to break 24 hours but I want to do it in one effort."
Of course, he's planning to do it solo, just himself and the event. And the time won't really matter, the aim will be simple 'to finish is to win and to win is to finish.'