Ironman Nutrition – Could your eating & drinking make you ONE HOUR FASTER?

Here in Melbourne everyone’s starting to get excited about the upcoming Ironman Asia-Pacific Championship, which is just a few weeks away. I’ve got several clients fine tuning their preparations for March 25th. So I thought it’ be a good time to look at the influence that nutrition can have on an Ironman performance.

In the past I’ve worked with many clients to improve their Ironman nutrition, and the results have been fantastic. Some have smashed Personal Bests by well over 30 minutes, and the feedback is usually along the lines of “it was hard to get used to this nutrition strategy, but when I did it made a massive difference”.

So I then went back through the sports nutrition research literature and decided to look at just how much difference a well executed eating and drinking strategy can make. The end product is this collection of Ironman nutrition strategies, which when executed properly could slash up to ONE HOUR off your Ironman finishing time.

A quick comment about the research

Before I delve into the strategies that can make a difference on race day, I thought it wise to make some general comments about the quality of research this is based on. Despite the surge in popularity of ultra endurance sports, the majority of studies on “endurance performance” centre on exercise durations of less than four hours. Why? Well put it this way, how would you like to turn up to a lab every weekend for four weeks, exercise on a bike ergo or treadmill at race pace in a laboratory whilst breathing through a mask and having blood samples taken, then be motivated enough to give your best possible performance? Now imagine doing this for 8 hours?  It’s unlikely that you’d get many athletes willing to subject themselves to that sort of torture, and even if they did it’s unlikely that they’d stay motivated enough to give a true performance over that duration outside of real competition.

Why does this matter? Because we don’t know for certain how the benefits found in performance over 2-4 hours translate into performance over an Ironman. The benefits in some cases may be smaller than what I’ve suggested here (my hunch is that this might be true for carbohydrate loading, caffeine and nitrate supplementation), whilst others might be greater (probably for adequate hydration and optimal carb intake during the race). But this is based on my personal opinion and estimations, as the research simply doesn’t exist to guide us.

But assumptions aside, let’s get into the exciting part – analysing how you could go up to an hour faster on March 25th.

Carbohydrate Loading – Arriving at the start line with muscles full of carbs

In my experience carbohydrate loading is well known but poorly executed by the majority of triathletes. Most simply have no idea exactly how much carbs you need to eat to do it properly. Having measured dozens of athletes at triathlon training camps, the majority eat around 5-6 grams of carbohydrate per kilogram of their body weight the day before a race. But to carb load properly before a big race you’ll need to eat 8-12 grams per kilo. For most people this is takes an enormous amount of food compared to their usual diet – click here to read a previous post which shows you what it looks like in food.

The performance benefits from carbohydrate loading have been measured in a few studies. They find a benefit of around 3-4% to performance over durations of 2-3 hours. We don’t know exactly what that’d translate to in an Ironman, but my guess is that the effect would be a bit less because the 500g or so of carbohydrate that you’ve stored will have to be rationed out over a longer duration. But it’s a good starting point, and if you arrive at the start line of IM Melbourne properly carb loaded you’ll definitely have an advantage over those who just “ate a bowl of pasta the night before”.

Approximate time saved over an 11hour Ironman (compared to moderate carb loading): 20-25min

Carbohydrate during the race

The science of carbohydrate intake during ultra-endurance racing has come forward in leaps and bounds over the last 10 years, mainly due to work from the University of Birmingham (and confirmed by others) showing a benefit to performance of a combination of carbohydrate types, when consumed in very large quantities (over 60 grams an hour and up to 120 grams an hour).

The main points from this work are:

  • The amount of carbohydrate that an athlete can get into the body from food is probably limited by the rate of absorption from the gut. Interestingly the rate of absorption is not related to body weight, so think of race day intakes in grams per hour, NOT grams per kg per hour as has been done in the past.
  • All carbohydrates digest down into one of three sugars in the gut – glucose, fructose and galactose. These are then absorbed across the gut wall and into the blood where they provide a source of carbohydrate to the working muscles during exercise
  • The quantity that can be successfully absorbed through the gut wall is around 60g an hour of glucose and 30-50g an hour of fructose. Regularly consuming large amounts of carbs whilst training may help athletes to increase the amount of carbs that the gut can absorb.
  • Galactose competes with glucose for absorption through the gut wall (and is less efficiently used once in the blood) so is best avoided during exercise. That’s pretty easy because it’s only found in milk and some milk products.
  • Consuming a combination of glucose and fructose in quantities of up to 120g an hour has shown to be performance enhancing, compared to less carbs or all the carbs coming from glucose (as any more than around 60g and hour will not be absorbed anyway).

So how much benefit do high carb intakes from a glucose and fructose combination provide? The lab studies suggest the benefits can be enormous, at least over 3 hours of exercise – as much as 18% faster than consuming no carbs at all, and 8% faster with 90g an hour of a glucose/fructose mix compared to 90g an hour of glucose only.

The final piece in this puzzle is some observations from the 2009 Ironman Germany and the 2009 Ironman World Championships. Researchers measured the carbs consumed by 107 athletes across the two events, and found a correlation between the amount of carbs consumed and finish time (see the graph below). In fact 30% of the variation in finish time in Hawaii and 20% of the variation in Germany could be explained by the quantity of carbohydrate consumed alone.

Note: Many people will struggle to consume this quantity of carbs during exercise. It is thought that the gut can adapt to better tolerate these higher quantities. Always try your race carb intake beforehand in training, and if you don’t tolerate these quantities slowly build up to it in training.

Approximate time saved over an 11hour Ironman (compared to moderate carb intakes): 45-50min

Race Day Hydration

Hydration is an interesting one to look at, mainly because most of the studies over the last 80 years were not designed in a way that allows us to actually work out the real benefit to performance. Most of the studies are Time To Exhaustion studies, meaning that they measured how long you could perform at a fixed intensity. But of course in the real world the exact opposite is true – the goal is to complete a fixed distance in the fastest possible time.

Some hydration studies also compared athletes taking sports drink or no fluid at all, and concluded that the difference in hydration influenced performance. They of course completely missing the point that one group received carbohydrate from the sports drink whilst the other group received nothing, which we know will improve performance in the sports drink group!

To date there’s only two studies ever published that have compared different quantities of fluid intake during exercise in a time trial format (as opposed to fluid Vs no fluid at all). And of these two studies only one used an exercise duration of over an hour to measure performance. The finding from this study (an 80km cycling time trial) was a performance benefit from ad libitum fluid intake (drinking as much or as little as desired) compared to no fluid at all of 3.2%,but no further benefit from complete replacement of sweat losses. However there’s no way of telling from the study what the participants defined as “ad libitum” fluid consumption – did they have pre-conceived ideas about how much to drink (or not drink), were they guided by thirst or something else? Much more research is needed for us to say with any certainty exactly how much fluid needs to be consumed during ultra endurance exercise to optimise performance.

It’s also difficult to suggest exactly how much difference hydration would make over an Ironman distance. The benefit was 3.2% over 80km of cycling compared to no fluid intake, but the difference is likely to be even more significant over 10 hours plus of racing, as the differences in hydration will become greater with greater accumulated sweat losses. But I’ll stick with 3.2% as a conservative figure for now.

Approximate time savings of adequate fluid consumption compared to inadequate fluid consumption over an 11hour Ironman (note it’s currently difficult to define what “adequate” actually is): ~20min

Caffeine before/during the race

Of all the other sports supplements used by ultra endurance athletes, none has received more attention than caffeine. And the research is pretty clear on the benefits – around 3-5% over durations of 2-4 hours, using doses of 2-6mg of caffeine per kilogram of body weight.

How does it work? It was previously thought that caffeine increased fat metabolism and spared carbohydrate stores. However this has since been refuted as the reason behind the performance benefits. Instead, sports scientists now believe caffeine has a direct effect on the brain and nervous system, allowing athletes to “feel” less fatigued and pace themselves more aggressively during exercise.

Again the effect over longer durations of exercise is not well studied – it’s possible that the effect may be diminished over a longer time because there’s less physiological reserve left to spend, reducing the effect of more aggressive pacing. On the other hand, it could also be argued that the effect would be greater, because the importance of reducing the perception of effort becomes more important the further into a race you get. Only time (and research) will tell.

Note: Not everyone responds the same way to caffeine. For some it makes little difference and for others it increases anxiety or makes performance worse. Always try caffeine doses in training before using in a race.

Approximate time saved over an 11hour Ironman (compared to no caffeine intake): 20-33min

Beetroot Juice – A new supplement for endurance athletes?

About two years ago beetroot juice burst onto the scene as the next big thing in sports supplements. The theory being that the naturally occurring nitrates in beetroot juice somehow enabled the body to produce the same physical effort for less oxygen, therefore making the body more “efficient”. Definitely a potential advantage for Ironman performance.

But until the last few months the studies on nitrates and beetroot juice simply showed changes in the body’s use of oxygen – there were no studies to show whether this translated into actual performance benefits. It wasn't until in mid-2011 that the first study was published measuring the effect of beetroot juice on performance, albeit only in a short cycling time trial. In this case the benefit to performance of 2.8% over 4km and 2.7% over 16km. Another study has been published just a couple of weeks ago, where well trained cyclists rode at a steady pace for one hour then completed a 10km time trial. This study also showed a benefit from beetroot juice, this time around 1.2%.

But Ironman is not 75 minutes on a bike. There are currently no studies over longer durations so we can only speculate on what the results might be. There is a sound theoretical rationale that beetroot juice could enhance Ironman performance, but we just don’t know if this will prove to be the case.

If you do decide to give beetroot juice a go, be aware that making your own (or drinking the juice in a can of beetroot) will not guarantee that you get the benefits. The amount of nitrate in beetroot varies greatly and declines rapidly if they aren’t juiced fresh. You can purchase high nitrate beetroot juice in Australia – it’s mainly sold in health food stores. There’s two types of products, normal beetroot juice (mixed with apple juice to improve the flavour) and concentrated beetroot juice. You’ll need to drink about 300-500mL of the former and 70-140mL of the latter to get the desired effect, about 2-2.5 hours before the race. We don’t know yet if the effect wears off after a couple of hours, but from my experience I wouldn’t recommend trying to drink beetroot juice halfway through a race unless you’re completely confident that you’ll tolerate it.

Note: Consuming this quantity of beetroot juice will make your urine turn pink for a short time afterwards. This is normal and harmless.

Approximate time saved over an 11hour Ironman (compared to no beetroot juice intake): unknown

Final Thoughts

This is far from an exhaustive list of nutrition strategies that might benefit Ironman performance. Colder fluids and pre-cooling with ice slushies also come to mind as potential strategies if it’s a hot day. But there’s more than enough here to try in the next five weeks of training to help you gain you some minutes in the race. If like most people you’ve got room for improvement in all of these areas, it’s likely that you will be able save yourself up to an hour on race day, possibly even more. But remember to practice these strategies in training first to avoid catastrophe in the race. As one sports scientist and nutritionist said “Most people train their body, some train their brain, but very few train their nutrition”.


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