What’s the Minimum Training Needed for a Full IRONMAN Triathlon

I’ve finished nine IRONMANs thus far in my triathlon career. All of my finishing times have hovered between the 8.5 and 9.5-hour marks. Now before assumptions are made, trust me when I say I’m not trying to gloat. After all the suffering and the tumultuous emotions experienced in these races, I simply cannot fathom how most athletes are out there hell-bent on finishing no matter what the cost – for 12, 13, even 17 hours!

I’ve said it before and I’ll say it again: these IRONMAN athletes are tougher than I’ll ever be. I know with certainty that the men and women pushing forward for that length of time are experiencing more pain longer than what I had to endure.

Speed is subjective. For someone like Tim O’Donnell, a 9-hour flat time at IRONMAN Arizona would be a disaster. When it comes to finishing an IRONMAN, what matters most is capability. Therefore, the answer to “What’s the Minimum Training Needed for a Full IRONMAN Triathlon?” is a bit nuanced.

For some, the answer pertains to simply finishing and nothing more than that – “How do I make it across that line before the cutoff time?” This is the end goal under the conditions and capabilities of their current physical state. For others, however, the minimum training needed will be relevant to a finishing time much faster than the 17-hour cutoff.

Yet for all triathletes, IRONMAN training and preparation is, at its lowest common denominator, intended to avoid the dreaded bonk. Therefore what you need is a projection of what you’re potentially capable of and then the ideal training to reach said potentiality.

In other words, if you’ve learned that it’s possible you could finish IRONMAN Canada in 14 hours, then what’s required to make that a reality?

Race Projections

First, let’s talk about how to know your IRONMAN capability. There is, of course, no entirely conclusive way to know your full iron triathlon potential until you actually complete one. However, there are surprisingly intelligent ways to project overall finishing time and splits based on your current athletic condition.

“Threshold capacity” is the key phrase here. What is your average threshold pace for one hour at an “all out effort” for swimming, cycling, and running respectively?

In the TriDot Training System, we refer to these numbers as “functional threshold,” and we quantify your average pace along with heart rate and power (if relevant) into a single numbered score known as the TriDot Score.

With your TriDot Score along with your physical characteristics, such as age, weight, time in the sport, etc., we’re able to project your capability of race time, with splits in each discipline, across a wide array of triathlon distances.

But let’s not get too far ahead of ourselves! Understand that your functional threshold capacities are usually found in short intense time trial tests. For example, we use a 5K run to determine your current running functional threshold. An IRONMAN marathon, on the other hand, is a lot longer than a 5K. So it’s important to note that your split estimation for the IRONMAN marathon is assuming that you’ve done the required stamina training leading up to the event. We’ll get to more of that in a minute.

Additionally, what’s really unique with how TriDot has implemented its data-driven system is that we can actually take your threshold capacity and measure it against any IRONMAN course due to the known data of each scheduled event. TriDot has actually created an entire site dedicated to this and it’s called IronIndex.

Iron Index uses your threshold and physical factor data along with known information about the terrain and climate of an IRONMAN course, the strength of the field based on past results, and your body mass variance to determine personalized finishing time and splits (and even potential age group placing).

IRONMAN Training

So now that we know how capable you are of finishing an IRONMAN triathlon before ever touching the race course, the next step is to actually train based on the knowledge of that projection.

An entire book could be written here (and has been many times before). But what’s good about knowing what you’re potentially capable of beforehand is that now we can be realistic about how much time you’re going to be spending in the swim, bike, and run respectively.

For example, let’s say your threshold capacity and physical factors tell us that your IRONMAN triathlon bike split will most likely be 6 hours and 25 minutes. This informs us of a couple truths. One, if your functional threshold on the bike doesn’t change, you will need to train on the bike in such a way so as to increase your stamina until you’re capable of cycling at an IRONMAN pace for 6.5 hours.

This generally means gradually increasing your longest bike session each week until that stamina goal is reached.

The other truth, however, is that if we increase your functional threshold we could be looking at a projected split of 6 hours. Under this new functional threshold you would actually be required to train less in order to reach the stamina goal (again gradually increasing longest bike sessions).

This is a major reason TriDot advocates power threshold training before stamina training. If we can increase your functional threshold early, before the major stamina training is required – and this will depend on your IRONMAN schedule timeline – then the volume of later training (and wear and tear on your body) will be less because you’ll be finishing faster!

TriDot’s “fast before far, strong before long” line of thinking is intended to not only be logical, but also to reduce the chance of injury and to give you more time to recover outside of triathlon training.


TRIDOT TAKEAWAY: The minimum training needed to finish a full IRONMAN triathlon depends on your race capability. With that knowledge, proper threshold and stamina training is implemented in order to match your projected goal most effectively.


TALK WITH TRIDOT: Do you know what your triathlon threshold capacities are? What minimum training do you need to do for the full IRONMAN triathlon?


JARED MILAM is a professional triathlete, TriDot coach, and member of the Tri4Him Pro Team. He has 16 years of competitive running experience and 11 years of competitive triathlon experience with a half Iron PR of 3:59 and a full Iron PR of 8:30. Coaching under the TriDot system since 2011, Jared loves working with aspiring triathletes of all ages and performance levels.

Patents applied for in the U.S. and abroad. Trademarks of Predictive Fitness, Inc. include nSight, TriDot, SwimDot, BikeDot, RunDot, TrainX, RaceX, Physiogenomix, EnviroNorm, eNorm, IronIndex, Optimized Triathlon Training, Normalized Training Stress, NTS, and Training Stress Profile.

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