My favorite training session of all is what we call big day training. I just love how epic it feels. I love the idea that on any random Monday while the rest of the world rolls into work I could be doing 80-90% of an Ironman in training. Of course I it takes months and even years to build up to this sort of session. I start with a more manageable big day but the fitter I get the bigger the session gets. We start BDT early in the season and gradually build it up until we hit about 7-8 hours. Click on through for the details of this monster day.

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From smoker to back of the pack triathlete to the Ironman World Championships.

Read about how I overcame all of the odds and discovered what it would take to get to the Ironman World Championships – my eBook is now available to buy as an eBook on Amazon UK, Amazon US, Barnes & Noble, and iTunes

It is also available as a paperback at Wheelworx.

For me at the peak it’s a 3800m swim, a 180k bike and a 1 hour run. Which gets us about 90% of an Ironman (the only bit that’s missing is the only bit you can’t really replicate in training and the most unique element of Ironman, the last two hours of the run)  When I get through a day like this and can go out and train again the next day as normal I know I’m getting into really good shape.

Related Post: #mykillersession part 1

As I said we start with a much shorter version early on in the season. Initially I need to be able to just cope with a long ride every week. When we get this to 5-6 hours with a large portion spent at IMRP we add in a brick run off it. This will become a staple session through the main part of our training block.

In 2013 while preparing for my second time to qualify for Kona for we added a swim to this session. I would start the day with a 3-4K straight through swim before dropping home for breakfast and to get on the bike. In the early weeks I would initially do 4 hours but this would build to 180k with a large portion at IMRP.

Depending on what part of the year and how fit I was I’d run straight off the bike for between 30-60 minutes. If the bike had been hard it would be an easy run but on a day that the bike hadn’t been too challenging I’d build to race pace for the second half of the run.

The last step was to do it as a race simulation so we would set everything up as we would for an Ironman. There would be no stops for breakfast or lunch. Each transition would be done as if in a race. We would ride from the pool and run straight off the bike.

The idea was to test nutrition, pacing, clothing, equipment, position and as many race day specifics as possible as well as getting as close to the physical demands of an Ironman as possible in training.

Related Post: #mykillersession part 2

Because of our work hours I usually did this session on Monday after working the weekend and I always felt very fortunate to be able to spend an entire day swimming, cycling and running while everyone else was in work. I’d often leave at 7 to go to the pool and arrive home at 4-5 pm just in time for dinner. One of my favourite aspects of these sessions was how you felt afterwards. The confidence I gained from doing one of these every week was massive. They made me feel like a real athlete. I loved the challenge of doing something incredibly difficult solo.

I imagine it felt like what the early triathletes experienced in stretching their limits physically and mentally. In discovering what was possible. When I listen to interviews with athletes like Paul Huddle or Scott Molina it’s one of the things they talk about. The sense of adventure and exploring their physical limits.

How do you start to incorporate BDT into your training? 

Firstly we make sure that we are comfortably able to do a long bike every week. In the early phases of training it’s just a case of getting out and riding. Slowly we add strength work and then we introduce race pace intervals.

Once we can do a long ride with long Ironman race pace intervals we will add a brick run. For the first couple of weeks it might only be 10-20 minutes off the bike but it will eventually build up to an hour running off a 5-6 hour bike.

Once this is a staple of the weeks training and I’m able to manage it we will add in the swim. We might take the bike and run distances down for the first couple of weeks before building up to the peak day described above.

Related Post: #mykillersession part 3

Contrary to what you might think the most important aspect of this type of session is not the physical gains from the massive overload but how quickly you can recover from it. Surviving a massive training day but being unable to train for the rest of the week can actually have a negative effect on fitness gains. If you average out the benefits of training 2-3 hours a day 5 days a week and a big day of “only” 4 hours over 3 months versus having one or two monster days of 6,7 or 8 hours but missing 10-12 days of proper training as a result means that the BDT is possibly having a negative effect overall.

Big days must always be balanced with the ability to absorb and recover from them. While I find that they are one of the most fun sessions they are incredibly challenging and must be built up to very gradually.


How many times have you heard someone tell you they were having the race of their life until they cramped or ended up with stomach issues or vomiting or diarrhoea or dehydration which was caused by the weather conditions or some other mysterious external force?

In my experience (often painful, personal experience) these problems are almost always caused by three main things.

  1. Ironman is longer and harder than anything we’ve done before and we are pushing our limits so things will invariably fail.
  2. Poor pacing judgement. Starting too fast, particularly on the bike is one of the biggest mistakes people make. They often realise after 30-60 minutes and slow down but at this point it’s too late.
  3. Not knowing how much or how often to eat. Eating nothing other than sugar based food and drinks for 10, 11, 12 or more hours is likely to cause even those with the strongest of constitutions problems. Energy food won’t make up for a lack of fitness or poor pacing, in fact it will likely make things worse.


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If you are only learning how your stomach copes with food and drink at your target race pace on race day you’re likely to run into big problems. Practicing this in training every week for months means that you will know exactly how much and how often to eat during the race and that you are very likely to eliminate two of the biggest mistakes people make in Ironman.

These are probably the biggest benefits of big day training, even more than the fitness gains. Learning how to race during training means you are much more likely to have a successful day when it comes to your Ironman.

Related Post: #mykillersession part 4

It’s usually overlooked but knowing how to get 100% out of your current fitness by nailing all of the important details on race day will almost always get you a better result than the supposedly “faster athletes” who only reach 80-90% of their physical potential because they make mistakes in their nutrition or pacing.

You can follow my blog right here as I document my training as I attempt to qualify for Kona again.

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Related: #mykillersession: all posts

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Thanks for reading


Chasing Kona eBook available

From smoker to back of the pack triathlete to the Ironman World Championships.

Read about how I overcame all of the odds and discovered what it would take to get to the Ironman World Championships – my eBook is now available to buy as an eBook on Amazon UK, Amazon US, Barnes & Noble, and iTunes

It is also available as a paperback at Wheelworx.