what is the key factor in finishing an Ironman?
Surely it must be a bit of both? Not having done an ironman (yet) I found middle distance to be a mental and physical challenge.
Seems a bit of an odd question with only two available answers....
The six months or so of carefull progressive training will provide plenty of mental strength and the fitness required to complete the event.
Staying inside your general race plan and targets on the big day will also help...we can all get carried away after months of hard graft and a short taper period...
You also need an element of good luck...my wife was knocked off her bike at about the 160km mark at Swiss IronMan this year by a twit in a black Audi. Lots of training, heaps of mental grit but she was just unlucky on the day.
So I would say that preparation and planning will make it happen...plus a fair wind on the day...good luck.
I think it is a bit of both. You normally find that most people who attempt Ironman are both physically and mentally prepared compared to people you see attempting to finish a long cycle race or ultra marathon.
Another important factor would be keeping your motivation levels up during your training in the months leading up to IM.
fitness has to figure in the equation but you must be mentally strong to realise that you can do the distance(personally I have to be mentally strong enough to keep recalculating my cut off times so I do not get D'Q'd).Nutrition must figure somewhere even if it is trying to stop your food/drink from reappearing over your trainers during the race.And then there is the matter of 'is your wallet strong enough to support you throughout your Ironman campaign'.And is you relationship/marriage strong enough to take the training regime.And......
the question is what is THE key factor out of the two - not what are the may factors that make up finishing an ironman. So out of the two options I'd say if your fit, but mentally not up to it you're not going to finish. I trained for and finished IMUK, but I did all that training with someone else or a group of people. The lone sessions were few and far between, so come race day when I was on my own I really struggled to finish it. My individual swim time, bike time and marathon time put me in the 12 hour bracket (factoring in a hour for fatigue) but I dragged myself across the line in 14 1/2 hours. It was all in my head.
Mental strength and fitness go hand in hand and are products of each other. As fitness develops mental strength and confidence grow. In finishing an ironman though I think fitness is the egg before the chicken.