Calculate Ironman Target Cycle Intensity

by Mary
(Sydney, Australia)

Just did my first Ironman and I want to improve my pacing. My weekend long ride was usually between 100 and 140km or 4-7 hrs. These sessions were very hard as I was constantly fatigued.

Took care in the race to hold back and not make the mistake of going too hard and burning myself for the run but in the end I think I went way too easy on the ride and the run.

I ended up unhappy with my bike speed average 23.7km/h and my run was 4.5hrs and other than very sore hips for the second half of the run I finished easily and my heart rate rarely got above 135 the whole race.

Kept expecting things to get tough and my heart rate to go up but it never did?

So how do I calculate how hard to push in the ride and in the first half of the run next time?

Intelligent Triathlon Training replies:

First of all, congratulations, the training you have done has obviously given you a good base that enabled you to be able to complete the Ironman relatively comfortably.

It is a much more positive experience in your first Ironman to find it wasn’t as hard as you thought it would be and know you could go faster rather than blowing up and it going completely wrong. Now you have a reference point to build from.

Something to consider is: what was the difference in intensity between training rides and Ironman, in terms of heart rates? It sounds like your training rides were little harder than you would want to race in an Ironman, so in future training you now need to find a comfortable balance between the two.

If you know what pace you set out on this time, the simple answer is, next time, set off a little faster! Really only experience can guide you, and you obviously also need to be sensible with regards taking into account weather conditions and the course.

Speed during the event is a difficult one to judge due to hills etc, so parts of the race might be faster or slower. So heart rate is a good indication of intensity but bear in mind that your heart rate can drift upwards towards the end of a long event for the same speed, as you get dehydrated.

If you have no power meter on the bike, heart rate is the safest way of judging intensity because you can compare it with known training experience. Although it doesn’t respond too quickly, it does respond quick enough that if you go a bit hard on a hill or push on too much you would see this and be able to react before doing too much too hard.

This is where the combination of experience from training and the experience of your first Ironman comes in useful as you can now relate the two.

Bear in mind that even people who have done a lot of Ironman races will finish and think they could have gone harder! But it is better to finish like that than not finish at all because you’ve gone too hard.

You’ll learn more from going a bit too easy than you will from going too hard and not finishing.

Remember that nutrition plays a big role as well – if you go a little harder but don’t fuel as well, you won’t go any faster as you’ll pay for this later in the race!

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