Why Doing a Spring Marathon is a Bad Idea for a Summer IRONMAN

For many people, a spring marathon is an important stepping stone for an IRONMAN in the summer. However, is it really the most sensible idea? Can there be occasions when it should be in the training plan? Many people need a marathon as a way of psychologically preparing themselves for an IRONMAN, but is that the most sensible thing to do from a physiological perspective? Read on to find out more.


Completing a marathon is a big deal. And yes, the fact that it is just stuck on the back end of a long swim and cycle in a long course triathlon is completely crazy!  

Let's start by thinking about the training effect you would achieve by completing a marathon. We know that a marathon is 42.2km, and we also know that generally people who feel like they "need" to complete a spring marathon are likely to be doing their first long course triathlon and therefore are unlikely to be at the faster end of the course. Therefore, times could be anything from 3.5 hours to over 5 hours or even longer. This means that the training load incurred is likely to be about 250-400 TSS points which is a significant amount – for most people it is going to be more than half their weekly training load! Assuming a fairly consistent 150 strides, 75 each leg, per minute, that is up to 22,500 strides. That is a lot of load going through your body and requires adequate conditioning and training for it. Are you ready for this in the spring?

Why is a spring marathon a bad idea?

There may be occasions when a marathon is actually a good idea but this is usually only for faster athletes or those with a very strong running background. However, even with a strong running background, they may be better placed by doing more cycling rather than staying with their preferred strengths! Below we outline five reasons why a spring marathon may not be the smartest move:

1. You Aren’t Fit Enough!

This sounds harsh but a marathon is tough. Running it well is actually hard. To be marathon fit in spring but IRONMAN fit in the summer isn’t completely aligned and inevitably, you end up not doing one properly. To run 4-5 hours straight is no easy feat. To do so off the back of some hard IRONMAN training is even harder. You will be wanting to fit long runs (160+TSS points) into your training regime. However, trying to fit it in at the same time as when you are trying to develop strength on the bike is certainly going to end with your running when fatigued and that can lead to injuries quite quickly. As mentioned above, this Spring Marathon tactic is usually for those who are newer to the sport as a way of proving that they can do each distance individually. The physiological benefit is unlikely to serve the desired purpose as it is likely to be much more volume and stress than you are used to! Generally speaking good runners don't need to run more than 2 hours at one time for marathon training. That may be at close to 200TSS points which is a big day of training. For many athletes, that could be close to 25% of your weekly training load in one session, or even more. Why would you spend all that on running one long run in preparation for a marathon? You won't have time to do that adequately. Wait three months, and the training effect from all three sports will be in your system and making that jump in distance far less stressful! The chances of you being run fit for it are slim at best and if you do prioritise it, then the points below stand more true (in particular points 4 and 5).

2. It Takes Close To A Month Out Of Your IRONMAN Training

A marathon will interrupt your training schedule. There is nothing you can do to stop that unless you are very well trained and fancy a long bike on the day before the marathon as a specific back-to-back session (but this is only recommended for strong athletes). You also need to consider the weekend of the event. The week before you are likely to be tapering into the event and can't train normal hours or intensity. The week after you are likely to be still recovering and it isn't until the week after that you will start moving properly and feeling less tired. There is an old saying that you need one day per mile to recover properly. This could mean over three weeks of recovery!!

This doesn’t bode well for the IRONMAN athlete looking to peak in the summer using the spring as a key building block to their training routine. Certainly it won't mean that this athlete can't train at all, but the training needs to be tapered, and allow for plenty of recovery before they get back into training as intensively as they need to again.

3. Planning

Inevitably, unless you are working with a coach who can allow for your races, few plans will suitably train an athlete for both a marathon and an IRONMAN. This means you will find you end up doing too much running and the training for the other two disciplines will not be balanced. In fact, I remember an old running coach who refused to acknowledge that cycling or swimming existed, so would continue to set run workouts accordingly. Even with a coach you will need to be careful!

Training plans will usually target one race or multiple races of a similar style. Planning for both can be very tricky as each athlete has very different strengths and weaknesses. It will be very tricky to peak successfully for the marathon without sacrificing a bike session's quality. Either you will be tired and not hit the targets, or you will end up missing them all together. 

4. This Can Lead To Injury And Fatigue

Most triathlete's injuries come from running. They generally end up hurting themselves through an overuse injury. Therefore, adding a higher volume of running either in training or through the race early in the season at a crucial building time for the IRONMAN is asking for a few extra straws on a camels back at a time when the camel is already feeling fairly vulnerable! Along with point 5 below, more running volume at the slower pace will be categorised as junk miles. These junk miles will feel critical and as they are likely to focused for the marathon it is very easy to ramp up the training stress a little too quickly and over stress as a result of the mixed sports or the large ramp rate/doing too much too quickly.

5. You Just End Up Practicing Running Slowly

Marathon running is slow and steady and there is a strong chance you will end up running or plodding round in the second half. By focusing on the quality sessions (which may well have a little bit more intensive work than long, steady runs) you are going to improve your running form. Running slow and steady usually results in less efficient running and just makes you very good at running slowly! Furthermore if you are concerned about your running (hence the need to do the marathon) the above points are even more exacerbated as you can gain more by working on form, hills or intervals with your running which will result in a faster marathon than if you just try and get the distance done! 

I don’t know any training plans that suggest a 3.5 hour run as part of training for an IRONMAN, so why should someone believe running 4-5+ hours as part of a spring marathon is suitable for a training for an IRONMAN? In my opinion, it is more of a question about the psychological need and that can be managed far more effectively with a coach or a suitable training plan for the IRONMAN itself and build your confidence in the sport of IRONMAN, not through a spring marathon!