Your Ironman Race Nutrition Strategy

In this blog we will show you how to prepare the principles of your nutrition strategy in 13 easy steps so that you can race with confidence in your next IRONMAN or 70.3 distance event. Getting your race nutrition right is an extremely personal process therefore there cannot be a 'one size fits all' approach; you need to take the time to apply to science to yourself and practice it in training. “And practice it in training” We cannot stress this enough!

1. Carbo-load correctly

Carbo-loading is an easy way of packing your muscles with extra fuel that you can call upon during a race. In the three days leading up to your big day, consume 10g of carbohydrate per kg of body weight (e.g. for a 60kg person this would be 600g).

Every morning during this period, drink 750ml of energy drink and wait 30 minutes. Then do a 10-minute warm up, followed by an all-out 3-minute sprint (this can be swim, bike, run or a brick). Get as much lactate build up as possible, then stop immediately. As a direct response, blood is then sent to these areas to get rid of the lactate, and in doing so, it brings with it energy which has been 'digested' from the energy drink. This energy is then stored in these muscles as glycogen, to be easily called upon on race day. Immediately following this intense burst of exercise, have a high carbohydrate breakfast. Throughout the rest of the day, you will need to ensure you take on board enough carbohydrate. This is done best in low bulk, energy drink from (keeps you hydrated too) and you can supplement this with a few bars and a normal athletic diet.


2. Know your sweat rates and your electrolyte requirement

Knowing your sweat rate is vital for a tailored nutrition plan. The equations below are a rudimentary way of checking how much you are sweating. Bear in mind, this changes with the environment and the sport, so if you are in a particularly extreme environment, it is worth testing it regularly before the event.

Sweat Loss = Mass before session, (kg) - Mass after session, (kg) - Total Fluid In (drink), (l) + Total Fluids Out (wee), (l)

Sweat Rate = Sweat Loss, (l)/Time(hr)

(N.B. 1L = 1 KG of water. (Water  density=1g/cm^3).) 

Repeat this test over at least 3-4 bike and run sessions. Try and get the test done in similar conditions to those that you will be racing in, as your sweat rates will vary a lot depending on the heat, humidity and wind. If it is very hot and windy you may not even feel like you are sweating as the moisture on your skin will evaporate directly into the atmosphere. If it is very cold, there will be some moisture loss through breathing, however this is usually deemed negligible in the sweat loss equation.

3. Do the maths

There are two figures you must know in order to plan how much energy to take on the bike and run. Your sweat rate (in l/hr) and how long you estimate racing for (in hrs). You will also need to know how much glucose and fructose your body is capable of absorbing. For most people, this is broken down as around 60g glucose/hour and 30g fructose/hour, so this is a good ballpark to start with. Some people find the fructose difficult to stomach, so this is one of the times you should be testing this out in training. Ladies, this can be dependent on the point you are in your menstrual cycle, so try it at various times.

How do we work this out? Take your sweat rate (in l/hr). This is the amount of fluid you must be consuming every hour during your race in order that you don’t get dehydrated or over-hydrated.

  1. Work out how much water is meant to go with every sachet of your chosen energy product. This will vary from brand to brand, but as an example, 1 x High5 Energy Source 2:1 sachet (30g glucose, 15g fructose) is designed to be taken with 500ml of water. 

  2. Now work out how many sachets you can take within the amount of fluid you need to take on board per hour. For example if my sweat rate was 500ml/hr, I could have just 1 sachet of High5 Energy Source 2:1 at the correct dilution per hour. 

  3. Does your energy intake equal around 90g/hour? If not, then ‘top-up’ the rest with gels, bars or other snacks of your choice, without exceeding 60g glucose or 30g fructose/hour. 

  4. If you are planning on using caffeine, your ability to absorb glucose into your muscles could increase to around 90g/hour (up to 100-110g/hr for well practiced athletes). Factor this in whilst doing your measurements more on that next.

For more information on how your body absorbs fuel, click here.

4. Caffeine: the legal stimulant

Caffeine lowers the neuron activation threshold, making it easier to recruit the muscles for exercise. It facilitates nerve impulse transmission; increases ion transport within muscles; increases the rate of glucose absorption by the muscles; increases concentration of ß-endorphins during exercise which reduces the perception of pain and it delays fatigue during exercise by blocking adenosine receptors on fat cells, and as a result increases the level of free fatty acids in the bloodstream which increases fat burning during exercise. All these factors make it a useful tool to have in your toolbox.

The best effects are seen with doses which ensure your body has between 3 to 6 mg/kg of body weight. However, caffeine has a half-life of 5 hours, which means that after having consumed 2 caffeinated gels, you will still have 1 gels worth of caffeine in your body after 5 hours. Overdosing (having more than 6mg/kgbw on caffeine is therefore very easy if you are not paying attention to what you are consuming throughout your race. The amount individuals can safely consume is directly proportional to their body weight, so plan your strategy carefully beforehand.

For short distance (Sprint or Olympic distance racing), caffeine-loading before a race is recommended. However, for 70.3 and Ironman distance events, we would recommend taking caffeine onboard during the race (rather than in a big dose before) in the form of caffeinated gels or caffeinated energy drinks, so that your caffeine levels are peaking as you are starting to feel tired. If you caffeine loaded a lot before a long distance event, it is likely that you would feel significantly worse during the middle and end relative to the start (even if you kept the caffeine intake high), due to general fatigue and this can play mental havoc with your race. All of this is of course very dependant on your own body weight and the time taken for you to complete the distance. A professional athlete who is aiming for sub 4hrs for a 70.3 distance event won't feel the negative effects of caffeine loading before a race nearly as much as someone who would complete it in 8 hours. 

For a deeper understanding on caffeine, read more here.

5. Get the salts in.

Electrolytes (dissolved salts) are present in blood, urine, in the fluid in and around cells and sodium, calcium chloride, magnesium and potassium are the most common electrolytes in the human body. Salts are essential for many heart, nerve and muscle functions, as well as regulating bodily fluid levels. Long course athletes are often worried about electrolyte depletion (hyponatremia) which can occur when the athlete sweats for an extended period, or consumes too much water without salts, leading to poor performance. For a deeper understanding read more about it here.

To estimate your own needs, assume a loss of approximately 500 to 800mg of sodium per 450ml of sweat lost. (If you have experienced muscle cramping in the past, err to the higher side of this range.) Using this sodium concentration and your estimated fluid losses, you’ll get a pretty good idea of your actual sodium needs. There are a lot of options out there on the market these days, including dissolvable salt tablets, some of which are tasteless. 

If you would like a more accurate understanding of your sweat rates, or your electrolyte requirement, we would suggest heading over to our partners: Precision Hydration. They can provide you with detailed analysis of your sweat make up.

6. Fill your bottles and prep your bike.

Many people find that for the bike leg, the most practical and measurable way of consuming enough energy is to have one pre-made syrup of energy drink and top up the other bottles on their bike with water/electrolyte on the way round from the aid stations. Many athletes tape gels to the top tube of their bike, or simply have them in their back pockets.

To make up the syrup we recommend using hot water making the powder much easier to dissolve. If you are doing a very long race, and are having trouble dissolving all of your sachets into your bottle, try floating the bottle in a pan of simmering water for a long period of time giving it the occasional stir. 

For the run, by far the easiest way of taking on board nutrition is to have nutrition in your pockets/on a nutrition belt and use the aid stations.

Remember: gels are often contain more glucose rather than fructose to reduce their sweetness. To get in the maximum amount of carbohydrate possible during the run, make the most of flat coke at the aid stations which contains fructose. (If you can tolerate the extra caffeine and the fructose)

7. Eat the right breakfast

Remember that your body can only absorb 60g of glucose and 30g of fructose per hour. If you eat a breakfast with 120g of glucose in it, you will need 2 hours to digest this. Make your breakfast  something you enjoy eating and eat on a regular basis so that your stomach is less likely to reject it whilst you are nervous. Porridge, bananas, cereal and toast are all reasonable options here. Whatever you end up having, divide the carbohydrate content by 60g and you will have a good idea of what time you need to start eating breakfast to ensure you aren’t still full when you hit the start line. Now you know what time to set your race alarm clock!


8. Wee whilst you ride!

A good indicator of whether your nutritional schedule is going to plan is how often you wee and the colour of your urine. Ideally during a 70.3 distance event you should wee at least once during the bike and during a full Ironman distance event at least twice. If you do get a chance to see the colour of your urine, it should be a straw colour, not clear and not dark yellow. Whether you get off your bike too wee, or whether you do the hardcore trick of weeing into your trisuit is down to you…but being able to check the colour is definitely worth the time lost at least once.

9. Have some nutritional insurance

You never know how long it is actually going to take you to complete your race. Any number of setbacks may occur, causing you to slow down, so make sure you are carrying a bit extra with you just in case. On the flip side- if you are steaming along much faster than you thought your would, don't try to gobble down all your nutrition in the shorter amount of time. Only eat and drink what you need for that time period.

10. Avoid the bonk

Consume energy frequently and steadily throughout the bike leg and the run leg. You should NEVER feel hungry during a race – this is a sure sign that you have not consumed nearly enough to keep you fully fuelled. Follow your nutrition plan and you will be very unlikely to ‘hit the wall’ or experience a real energy low or ‘bonk’. If you are doing a liquid only diet, you should also feel full along the way as well!

11. Get to grips with the aid stations.

It is always best if you don’t have to rely on aid stations to supply your race day nutrition (except water or course) however it is very handy to know what will be at every aid station just in case. Take the time to look up the location of the aid stations beforehand too, so you know when to expect them during the race. This will help you plan your nutrition strategy. If there is an aid station at the bottom and the top of a climb, maybe it is worth picking up the bottle at the top rather than the bottom and ensuring you finish drinking before the hill so you can focus on climbing.

12. Consider not using solids.

We would always recommend the less solid food the better, purely because it is slow to digest, contains protein, fat and fibre that you do not need whilst racing, and can cause digestive issues further on down the line in the race. This is personal preference however, and especially if you are planning on taking a long time over an IRONMAN whilst not pushing yourself too hard, then solids would probably work absolutely fine. Again though, we cannot reiterate how it is personal preference and how important it is to…

13. Practice practice practice.

Practice training with your nutrition plan. This doesn’t mean going out for a long steady ride sipping away at your energy drink and popping a few gels when you feel like it. This means measuring out everything correctly, and doing hard, long, race-pace sessions that will closely mimic your race conditions. Most athletes find that it is the sheer volume of liquid that is the most difficult to get used to, rather than the energy itself.

If you have any specific dietary needs or you still aren’t sure then we would suggest working with your coach and/or a nutritionalist to ensure you have the right plan for you.