Race fuelling for endurance sport: A review of 3 half-iron distance races

Over the 2016 season I competed in three middle distance Half-Ironman events. The choices made when choosing a fuelling strategy for endurance racing are such a key factor in determining performance that I thought it worth sharing. In this blog I will go over some of the approaches I took, and why as well as discuss what I found to work both physically and logistically. I hope this will help you in your search for endurance performance for you or any athletes you coach.

Ironman Mallorca 70.3 was my first serious attempt at a middle distance race having been racing competitively at the shorter distances for a few years, including two age group world champs. My decision to dedicate my season to racing middle distance was spurred on my two incentives; firstly, I’ve always seen my triathlon journey as working up to the longer distances. And, secondly having raced two consecutive years in international age group competition, I wasn’t expecting to see a huge difference in performance this year, so didn’t want to dedicate a year of training, racing and travelling for not much of an improvement.

The decision to race Mallorca was partly because if I was going to do a few middle distance races this year, I wanted one of them to be abroad. Having heard friends, club mates and clients talk about racing abroad, I was keen. I’d somehow managed to rope my other half into entering as well, and after a coffee and brunch with a friend of mine last year we all found out we had similar aspirations for 2016 and as he’d raced Mallorca before and loved it, we chose that. “At least we’ll be guaranteed good weather…” (more on that later!).

Arguably the biggest challenge in moving from short course to middle and long distance racing is executing a successful race nutrition strategy. Given the energy storage potential of the body we should all be able to complete a sprint distance triathlon with no mid-race fuelling, and even Olympic distance fuelling is more of a ‘top up’ to ensure you are able to keep the intensity high to the finish line. However, racing for over double that time means you’re almost certainly going to deplete your body’s glycogen stores. While all endurance sports will use a mixture of fat and carbohydrate stores as fuel, the exact ratio will depend on the atheltes’ ability to utilise fat as a fuel source at higher intensities, as well as what percentage of their VO2max (rate of oxygen uptake) that athlete is working at.

So let’s consider the limitations for performance for a half-ironman compared to a shorter distance event. Firstly; there’s the ability to sustain the intensity of output; how hard the athlete can work. For seasoned athletes with a good training background behind them you often see minimal difference between their sprint and Olympic distance swim, bike & run splits. However, when you step up to a new distance there’s an increased demand on the body, and this will take time to get used to. Periodising a training plan to allow adaptations to take place will not only improve performance, but is the safest way to avoid injury.

For the increase in distance there’s relatively little cardiovascular improvements to be had. The toughest adaptation the body has to make is to become robust enough to deal with the increased race distance. So training sessions should be designed with this in mind, as well as recovery nutrition on a day-to-day basis. Planning kcal intake around a training week can help avoid large differences between high volume and low volume days, by planning for more energy intake prior to and following longer training days.

The second limiting factor is ratio of fat to carbohydrate that an athlete uses for fuel depending on their exercise intensity. Because of the larger amount of energy that can be stored in the body as fat, compared to roughly 2000 kcal of glycogen stored in the muscles and liver, the sooner an athletes’ body switches over to carbohydrate as a primary fuel source, the more fuelling will have to be done mid race. The rate at which fat may be used as a fuel source will remain broadly the same in comparison to an individual’s percentage of their VO2max, however adaptations of endurance training will mean that more output can be achieved from the same effort; i.e. as we get fitter we can go faster for the same intensity.

Other methods athletes often use to increase their ability to use fat as a fuel source include fasted training; i.e. training early morning sessions before the first meal of the day. While many reading this are probably aware of the popularity of Low Carb-High Fat (LCHF) diets, I’m not going to touch on this in this blog; because this blog is about my experience, and LCHF could be an entire blog in itself. Plus, most people are usually in one camp or the other, and I’m not writing this to convert anyone. As a guide our optimal muscle triglyceride (fat) usage comes at around 65% of VO2max, with muscle glycogen (carbohydrate) being the dominant fuel source at around 85% of VO2max. So, race slowly enough and you can go for longer and take on less fuel, but you’ll be slower. Or, race harder, go faster, but require more fuelling mid-race. So while carbohydrate is still the best fuel source for higher intensity efforts, relying on it too much brings us nicely onto limiting factor number three;

How quickly can we consume and absorb energy during a race. This is probably going to be the vague answer you weren’t looking for, but it depends on the athlete. At around 70% of VO2max your body will start to reduce blood supply to the digestive system in order to increase availability to working muscles. So, work too hard and you risk the fuel you take on not being processed and sent to where it needs to be.

Triathlon fuelling by discipline; obviously on the swim there’s no aid stations or requirement to fuel (except in ultra-distance triathlon e.g. double & triple ironman & Decca racing). So if we focus on the bike and run. The bike is the most logical place to do most of the fuelling since the ability to carry fuel is easier. Working heart rate is usually a little lower than running at the same intensity which combined with the absence of vertical oscillation experienced in running means you’re likely to be able to consume and process more energy. While fuelling is about simply getting energy into the body, one obstacle will be the individual athletes’ preference or ability to take on certain products. While I’m fairly lucky that I can take gel upon gel with no unwanted effects, I’ve worked with those that have to switch between energy drinks, gels and solids (bars/fruit) so that they do not experience any gastric upset. On the run I usually advise athletes use water and gels since these are easier to process on the run.

Calculating energy requirement

When stepping up to a new distance a certain amount of trial and error in training combined with extrapolation from energy intake from shorter races is a useful starting point, however it’s important to consider that carrying unused fuel is better than running out and hitting the wall, or “bonking” as triathletes call it. If you’ve no data for a client or athlete, then your estimation should be generous as to avoid this. Sticking to the nutrition manufacturers recommendations for use could be a useful starting point, but what else can we use?

I used data from swims, bikes, runs and previous races recorded on my Garmin with a HR monitor to get an average kcal consumption per hour for each discipline. I then used my expected goal times for each discipline to give a calculation of the energy I’d require for the race. I also used an online calculator designed for helping athletes workout nutritional intake for triathlon (a link to which can be found at the bottom of the blog). The advantage of this software is that it took into account stored energy within the body as well as an estimation of the percentage of fat/carbs used, which is interesting because without this; purely working out energy intake based on estimated expenditure comes out with some alarming numbers for what you’d have to consume. Somewhere in the region of 34 energy gels for me, which is just ridiculous. But I’m sure many of you, like me have seen marathon runners and triathletes with energy gels strapped all over their bikes and bodies, who’ve probably used similar logic to conclude they need that much.

Using a mix of experience and the online calculator, my own plan was to take just one additional gel as a spare with me on the race, then rely on the aid stations if I felt I needed more.

IM Mallorca 70.3

Like all “M-Dot” races these are extremely well organised with plenty of aid stations on the bike course and run course. Because these aid stations are set up with water bottles, energy drinks & bars & bananas, and they’re very frequent, it’s possible to complete the race with purely the on-course nutrition. If you’re planning to do this however, you should make sure you’re training is done using the same nutrition supplier as the race, so that you can make sure you experience no gastric issues. Because I’m used to using a particular brand that I get on with very well, I opted to take my own nutrition, relying on the aid stations for water only on the bike.

Because of the practicalities of opening, storing and disposing of lots of energy gel packets, I decided to adopt a strategy I’d recently heard of; using a ‘Gel bottle’, containing all my intended gels mixed with an electrolyte drink in a 500 ml bottle. Obviously this mixture was a very concentrated mix, and would have to be taken with water to make it isotonic and aid absorption and adequate hydration. However, given that aid stations were regular it meant I could carry only one additional refillable bottle system, refilling it when needed. I opted for one solid bar around the half-way point for variety. The biggest advantage of this strategy was that taking energy was quick and easy, and I only needed two bottles on my frame. This worked really well for me, my energy felt good and the only improvement in retrospect was that I didn’t take on enough water because the weather was very uncharacteristically wet and cold, no-one had brought adequate layers since it just wasn’t expected and many athletes suffered. As a result it was hard to convince myself I needed more.

The run was hard to judge whether it was fuelling or my muscles being so cold that made it a struggle, I did take on a lot of electrolyte drink as I knew I was not adequately hydrated, but the addition of the two scheduled gels got me through.

Alterations to this strategy would have mainly been better layering on the bike to increase body temperature, which would have encouraged more fluid intake.

Grafman British Middle Distance Champs

With a flatter and faster bike course, this was looking to be a much faster race. The weather started cold, but held out for perfect conditions. Aid stations were water and electrolyte only which meant all fuel had to be carried so I adopted the same strategy as Mallorca, with a gel bottle and refillable water system.

While water intake was adequately planned, the only mistake was on my second refill grab the bottle lid wasn’t on properly so as I squeezed it into my hydration system, a lot of it was spilled out. This left me a little short on water for the last 10 km, but fortunately I didn’t suffer too much.

Remembering the struggle of the run in Mallorca I’ve planned an additional gel in the second transition on top of the two I would take out with me on the course. Combined with the water at the two aid stations this worked well.

"On a side note, it’s worth planning gel intake just before an aid station as it allows you to wash down the gel with water, stopping you getting a sticky throat and ensuring a good hydration schedule too".

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Fugitive Middle Distance Triathlon (Marlow)

My third middle distance race of the year was to take place in July with considerably warmer weather than the previous races. I took the time a couple weeks before to recon the course, which took on three loops on a 5 km climb. This is always a great idea if you have the opportunity, since you can gain useful information that can help your race plan. Such as; road surface, tricky corners or descents as well as pacing climbs, since it’s hard to judge these from a race profile. I’d worked out where the best places to take on fuel and hydration would be, the only thing changing my race strategy was the on-course aid stations.

Much to the amusement of fellow club-mates and friends, I spent longer than I probably should have done trying to work out how to adapt my fuelling. The issue was, the race organisers had set up an aid station at the top of the climb, so we’d pass it three times. However, the litter zone was only at the beginning of the aid station, which is designed so that athletes can discard their empty water bottles, then pick up a replacement. However as I, and many other triathletes I know, use a refillable system, this was an issue, since what we’d ideally need is to pick up the bottle, fill up our on-bike system, then dispose of the empty. In the end I took the decision to carry two smaller bottles with my own electrolyte drink solution, given the expected weather and therefore water loss. Then, on my final climb I’d throw away one of my empties and grab a water for the remaining distance. The strategy paid off as I had biked up into first place and held onto a small lead coming into the second transition.

What this does highlight is that it’s important to be versatile with your race plan, since getting too caught up mentally in how you do things means you won’t cope well when things don’t go to plan. This is why it’s a good idea to have spare energy products in transition with a water bottle, then you’ve a back-up if you’re bike plan hasn’t worked, or something has gone wrong, like missing an aid station, or a bottle leak, or dropped energy bar/gel.

On the run it was the same plan as before fuelling wise 2-3 gels with water at the aid stations. With the hot and muggy weather I’d already decided more water would have to be taken on. The 4-lap course meant 8 potential aid stations, and I got used to drinking once per lap and using the other aid station to throw water on me to keep me cool. I ran my best ever run at that distance and despite getting passed early on, knew there wasn’t any more I could have done.  Running at a pace that was nearly ten minutes quicker than I’d done in Mallorca I’d taken on an additional gel from an aid station with 5 km to go as a ‘just in case’. With 2 km to go on the last lap, passing the aid station despite wanting a drink I knew it wouldn’t have time to make a difference, so just rinsed out my mouth and threw the rest over me.

Looking back it’s one of few races where I can say there’s little I’d have changed to my race plan that would have changed to result, or even my time over each discipline. Nutritionally I’d used a slightly different version of my original plan, but it’d worked.

Moving forward I’m keen to keep tweaking and trying different things, but ultimately the energy intake will be broadly similar, with the three main factors affecting the final strategy being the course profile, the event aid stations and the weather. So what can we take away from this? Well, while there is a lot of information available these days as to what and how to fuel. It’s important to make sure whatever strategy you choose is right for you, and that comes from a little research and a lot of practice.

Practical considerations when deciding a fuelling strategy:

  • Required energy intake for race distance
  • Athlete preferences or limitations with fuelling
  • Storage capacity on bike
  • Aid station frequency on bike and run course
  • Aid station set up & littering rules, i.e. if there is bottle disposal before/after or both at aid station.
  • Weather; temperature will affect required water intake regardless of energy intake. This may dictate liquid fuelling strategy effectiveness. Gels are more controlled intake, while water/electrolytes can be consumed on requirement

Nutrition calculator: http://www.tri-talk.com/TriTalkNC/TriTalkNC.htm

Blog originally by Phil Paterson