Fuelling for an Ironman triathlon is as much an art as a science. Knowing what to eat and when is crucial to peak performance. Many triathletes will tell you that their success comes as much from making the right nutritional decisions before and on race day as it does from completing the right training.
By race day, your training is in the bank, but fuelling is one area where you can make improvements or create problems that could cost you valuable minutes or hours, or even lead to the dreaded DNF (did not finish).
Experienced triathletes will tell you that the best way to prepare your gastrointestinal system for the fuelling challenges of the triathlon is by practising eating and drinking during cycling and running under simulated triathlon conditions. You must establish your own nutritional requirements through trial and error. Raisins might work for your friend, but they may send you running for the loo, so it’s important to try a variety of carbohydrate-rich foods and fluids to establish your personal preferences.
Your pre-race diet
The effects of tapering combined with carbohydrate loading have been examined in hundreds of studies, with researchers concluding that this practice improves triathlon times by two to three per cent – or 12-18 minutes off a 10-hour finishing time. You should eat a diet of around 60 to 70 per cent carbs for at least four days – and follow a tapering programme for at least a week – before an Ironman.
That means eating and drinking 8-10g of carbohydrate per kilogram of body weight per day. For example, a 72kg triathlete should consume 576g-720g of carbs per day. It’s also a good idea to consume a little more sodium and potassium in the three days before you race to prevent hyponatraemia (abnormally low sodium
in the blood).
Avoid alcohol in the days leading up to an event and stick to foods you are accustomed to. If you’re travelling overseas to race, that might mean taking your own food. Finally, in the hours leading up to the start of the race, eat a high-carb, low-fibre snack a couple of hours before the start, followed by a final pre-race boost of a gel or sports drink 30 minutes before the gun.
“The two primary goals of feeding the ultra-endurance athlete during the event are to maintain normal hydration and to maintain normal blood glucose levels,” explains sports nutritionist Nancy Clark, author of Sports Nutrition Guidebook. Seasoned triathletes will tell you the two golden rules of triathlon nutrition are to eat before you become hungry and to drink before you become thirsty – so you need to start eating and drinking early in the race.
Start taking in carbohydrates right from the start, and at regular intervals, to help you conserve the glycogen that you have stored in your muscles and liver, for as long as possible. You want your food or liquid to be absorbed as fast as possible to fuel your muscles and brain. And, no matter how good a job you do of refuelling and drinking during a triathlon, you’ll still burn through your stored glycogen toward the end of your Ironman.
Your goal during the race should be to replace 30 to 50 per cent of the calories you are burning. This equates
to between 2,500-5,000 calories for Ironman competitors. Considering you’ll burn 500-1,000 calories per hour (depending on your size, gender, and the temperature, terrain and intensity of the race), and that the Ironman lasts from nine to 17 hours, this will be a lot of food.
Research data on calories burned during an Ironman is quite staggering. At Ironman New Zealand in 1997, men expended, on average, 10,036 calories and consumed 3,940. Women burned 9,253 calories and consumed 3,115.
Aim to take in around 250 calories an hour from food, and roughly the same from sports drinks. Studies suggest that you’ll only be able to absorb this much food and drink if you slow down to around 60-70 per cent of your VO2 max (roughly two-thirds of your race pace).
So, your cycling and running pace needs to slow to permit digestion when you are feeding. This pace will be around your comfortable cycling cruising speed, and a fast walk to a slow jog.
Ideal times to eat during an Ironman are early in the cycle leg, and during the early stages of the marathon. You can even eat more solid, higher protein and fat-containing foods if you go slower for a while (See Solid Advice, below). Liquid canned meals also work well, or even chocolate milk.
Recent research has found that sports drinks with combinations of glucose and fructose, or maltodextrin and fructose, can result in reduced fatigue and faster performance. And you can take in up to 90g per hour of these mixes.
Maltodextrin is a high-calorie complex carbohydrate that is well tolerated and quickly absorbed, but be wary of drinks with fructose as they can cause stomach upsets, nausea, and bloating, so experiment with them in training. Beware of sports drinks or soft drinks with high concentrations of carbohydrate – above 10 per cent – because they take longer to empty from the stomach.
You should try to match your fluid and electrolyte needs with your losses on an hourly basis. Start your Ironman well hydrated by drinking 250-500ml of fluid in the hour before start time. Research suggests that once the race begins, you should drink at least one litre of fluid every hour. You are hydrating adequately if the colour of your urine is clear. If it is dark, drink more. You should be urinating about every two hours during an Ironman.
If you’re urinating every 30 minutes, temporarily cut down your fluid intake. Pay special attention to your electrolyte intake, especially sodium, through sports drinks or food. Hyponatraemia occurs in athletes who take in too much low-sodium fluid (water), so that the sodium levels in your plasma become too diluted. It affects around five per cent of triathletes in ultra-endurance events, with symptoms including bloating, nausea, cramps, disorientation and confusion. In severe cases it is fatal. Experiment with sodium tablets, or high-sodium foods such as crisps or pretzels. There are no clear-cut guidelines for sodium intake during ultra events, but 200-500mg per hour is enough to prevent hyponatraemia.
Also ensure that you take in enough calcium, magnesium and potassium in the days leading up to the race. Although the evidence is inconclusive, these electrolytes may help to prevent muscle cramps.
Taking in caffeine during the Ironman can be beneficial. Numerous studies have found an ergogenic (performance-enhancing) effect on ultra-endurance exercise when caffeine is taken an hour before the event. Doses of 1mg per kg to 6mg per kg have been shown to boost performance.
Fuelling for an Ironman is a complex process that requires experimentation to find out what works for you. Once you’ve figured out what sports drinks and foods work the best, you’ll perform better during the race and your time will reflect this. And remember that your fuelling begins several days before the triathlon, in conjunction with a well-planned tapering schedule.
To gel or not to gel?
There’s no scientific evidence to suggest that gels are absorbed better than standard sports drinks. If you prefer sports gels, avoid washing them down with sports drinks. The overall concentration will draw fluid from your gut, further dehydrating you, lowering blood volume and making blood more viscous (which makes your heart work harder). Dilute gels with water.
The following list of carbohydrate-rich solid food has a proven track record in Ironman triathlon, but experiment in training before you tuck into a pizza at the halfway mark:
Dried fruit, bagels, crisps, milkshakes, chocolate bars, biscuits, sweets, pizza, pretzels, boiled potatoes, energy bars, watermelon.
To determine what food and drink you can handle without adverse side effects, answer the following questions and write down your responses for future reference:
1. Which sports drinks and liquid meals work for you?
2. Which flavours of sports drink are palatable for you and how often do you need to swap them to prevent flavour fatigue?
3. Which foods can you stomach?
4. Which pre-race meals can you tolerate that give you the biggest boost?
5. How much can you drink without liquid sloshing around in your stomach?
6. Do salt tablets prevent hyponatraemia for you, or do they dehydrate you?
7. Can you tolerate flat soft drinks
to get a caffeine boost?