Pacing The Ironman - Part 2

After looking at some of the research on Ironman pacing, it is now time to put that information to use. An important overriding concept I am going to apply is that I will take a conservative approach. My goal is to set a personal best at this year's race. Something that I believe is well in my capability as long as I don't blow it. An almost guaranteed slightly slower time versus a chance for faster time, but with the risk of seriously blowing out is the choice. I'll play it safe this year.


I remember hearing a quote on one of the old Ironman videos, "You can't win the race in the swim, but you can lose it."

I'll extrapolate the results out from the research from sprint distance triathlon, but with the assumption that the results are magnified. So while 90-95% of time trial pace doesn't affect the bike leg at sprint distance, I assume that it is likely to at the longer distance. Therefore, I'll choose 80-85%. Over the next three weeks I'll test this with performing a couple of 4000m time trials in the pool for best time. Based on the times achieved I'll then perform a couple of efforts at 80-85% of the average pace to get an idea of what race pace should feel like.

It is this feel I will aim to carry into race day. Naturally there are a number of other factors that will affect the overall swim time. Wetsuit, drafting, currents and just the whole washing machine effect. On exiting the water, I may check my time out of interest, but then I need to forget about it. It is now time for the land based fun.


The overriding measure will be heart rate (HR). The trick will be too find an appropriate range, which is something I am currently working on in training. On race day I'll attempt to remain within this HR range throughout the bike leg, regardless of terrain and weather conditions. I'll expect a slight slowing of pace over the 180km.

Furthermore I aim to keep the effort smooth. No sudden jumps in intensity, no quick sprints over the top of hills, no picking it up just because I feel good. I'll expect a small increase in HR when climbing hills or going into a strong headwind, but I will keep these to within my target range.


Hard to predict too much here. Everything depends on what has come before it. My HR could be anything, and I have found in the past can it jump around a bit late in the race, so as a guide it is too arbitrary. This leaves me with feel.

My aim is to find a rhythm as soon as I can. Something I feel I can truly hold for the 42.2km. Once I have established this, I will check the pacing against the kilometre markers for 3-5km and compare this to what I achieved in training. This is my reality check. If I couldn't achieve it in training (which was for shorter distances), then it's not likely I can hold it in the race. I'll make the adjustments at required.

This pace I'll aim to hold to about 35km and then see what I have left in me.


  1. Thanks for some really interesting information and congratulations for considering your pacing strategies so carefully. My experience over 8 IMs is that my fastest race was the one in which I was most conservative. Whenever I tried to go hard and fast I would blow up and of course go much slower. I believe that by avoiding ANY efforts outside your aerobic threshold you will accumulate much less lactate in your system over the course of the day. Less lactic acid means much better fat metabolism - your stores of carbohydrate remain intact for longer, thereby also avoiding stress on your gastrointestinal system which is caused by pumping your stomach full of excessive amounts of gel and sports drink in eforts to stay fuelled-up. Go for a relaxed, even pace and you will go faster.


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