Ironman Triathlon: A scientific study of the nutritional recommendations in preparation & training of the event

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Ironman Triathlon: A scientific study of the nutritional recommendations in preparation & training of the event

Ironman Triathlon

A scientific study of the nutritional recommendations in preparation & training of the event
Fred is a student and is 21 years of age. He is 1.75m tall and weighs 68kg. He has a history of sports performance as he was a keen swimmer who won national titles in the 400m freestyle and competed at county level. Until university Fred had never competed in a triathlon however once he became interested during his university years he was seen to have good potential. Recently Fred at achieved a podium finish in his age category for the national triathlon championships which was over an Olympic distance (1.5km swim, 40km bike & 10 km run).

Luckily Fred has recently managed to gain a lottery spot in the World Triathlon Championship in Hawaii next October. This is an event which 1800 athletes participate in each year in Kona, Hawaii. It consists of 2.4 miles swim, 112 miles bike & 26.2 miles of running; of which must be completed sequentially and within the cut off time of 17 hours. The average temperature in Hawaii is 28-30 degrees, with a humidity of 70-75% and wind speeds ranging from 7-30mph.

Now after graduating he is focusing all his time on full-time training, and is aware that he will have to train within 30 to 40 hours per week if he is wishing to complete his aspirations of a podium finish in his age category. However due to Fred’s lack of experience in long-distance endurance events he is worried that he will not be fully prepared for the event. His main concern is how he alters his diet to cope with the demands of his training. Therefore this study will help Fred with his nutritional intake & when he should consume foods around the timing of his training program.

Firstly to be able to appropriately structure a diet around the athletes training schedule and to meet the demands of the training program the program must be taken into consideration. Such as, how much energy is expelled during the training? How intense is the training? And when are appropriate times which the athlete can eat around their training regime?

Table 1: Fred’s Training Program

Monday: 7:00-11:00 = Cycling average speed 18mph, 14:00-16:00 = Run 7:30 min/mile    , 18:00-19:30 = Gym (circuits, moderate intensity)    

Tuesday: 7:00-8:30 = Moderate intensity swim at 10 METs, 11:00-14:00 = Cycling average speed 20mph, 18:00-20:00 = Run at 7:30 min/mile

Wednesday: 7:00-11:00 = Cycling average speed 20mph    , 13:00-14:00 = Run at 6:00 min/mile, 18:00-19:00 = Gym (circuits moderate intensity)    

Thursday: 7:00-9:00 = Swim moderate intensity at 10 METs, 12:00-17:00 = Bike average speed 16mph, 17:00-18:00 = Run at 7:00 min/mile    

Friday: 7:00-8:00 = Spinning Class at 15 METs high intensity, 8:00-9:00 = Gym (circuits moderate intensity), 17:00-20:00 = Run at 7:30 min/mile

Saturday: 7:00-9:00 = Swim moderate intensity at 10 METs, 13:00-17:00 = Bike average speed 19mph, 17:00-18:00 = Run at 7:00 min/mile    

Sunday: Recovery Walk, 6 miles at 11 min/mile

As illustrated Fred will be training from as early as 7:00am therefore his nutritional intake from both the morning and the night before are essential if he is to have sustainable energy for the completion of his training. Also the recovery of his body’s muscles is aided through the types and amounts of food intake he has. Therefore what and when Fred eats need to be adequate for both the recovery of his body and to prevent muscle glycogen depletion before he trains again.

Carbohydrates are essential for athletes to raise their muscle glycogen stores and with the correct amount and time of consumption the carbohydrates can be fully digested and stored. Fred needs to consume CHO (200-300g) 3-4 hours prior to exercise, or if that cannot be achieved then what’s known as ‘loading’ should be completed the night before. This allows glucose to be available within the gut which can later be transported into the bloodstream and raise the energy levels; not only that but the ‘loading’ phase helps prevent the depletion of muscle glycogen stores during the overnight fasting the body encounters when sleeping. If Fred keeps to a diet of 88% Energy CHO & 12.5g/kg body weight daily then he will achieve what is known as supercompensated levels of glycogen which will allow Fred to sustain his training without having to lower the intensity of his training. (JEUKENDRUP, Asker E, JENTJENS, Roy & MOSLEY, Luke (2005) Nutritional Considerations in Triathlon).

Carbohydrates can also be obtained through fluid consumption. The main resources of these carbohydrates and electrolytes are found in isotonic sports drinks such as Lucozade. These drinks will help Fred in obtaining adequate levels of CHO during training & the event when food consumption is difficult. This will be extremely helpful for Fred as the Ironman Triathlon on average uses 8500 to 11,500kcal for the completion of the event; and due to the environmental conditions such as the heat an athlete can sweat as much as 2 litres/ hour, therefore these drinks help to require fluid and energy replacement and control the core temperature. Also to help regulate core temperature and prevent performance loss water needs to be consumed; however Fred must make sure that he does not ‘overdrink’ his fluids as this will cause Hypronatremia. This will have a negative result on Freds performance as it will dilate his sodium levels within the blood and can cause Fred to gain weight.

CHO are the most dominant sources of energy they cannot be used all the time. Even at high intensity exercise lipid oxidation provides 25-30% of the total energy; this is due to the limitations of CHO stores and therefore lipids become the main substrate during ultraendurance events such as this. (LAURSEN, Paul B & RHODES, Edward C (2001). Factors Affecting Performance in an Ultraendurance Triathlon) So Fred needs to be consuming healthy/ oily fats which are found in foods such as fish which contain high amounts of proteins and fats such as omega-3 & 6.

Protein can be overlooked during ultraendurance events such as this because it is not used predominately as an energy source however it is used for maintenance, growth and repair of the body, and not to mention its enzyme and hormone support. An average person needs 0.8g/kg body weight per day to sustain themselves, however due to Fred’s intense exercise regime he will need considerably more to repair his body. On average Fred will need to consume 1.8g/kg body weight. (HUTCHISON, Jennifer (2008) Power of Protein [online]). This means Fred will need to consume on average 122.4g per day from foods such as fish, chicken, beef and vegetables.

If Fred uses these recommendations and follows a structure shown in Table 2 then he should have a sufficient amount of nutrients to sustain his training and aspire to a podium finish.

Table 2: A dietary structure based around Fred’s training for the Ironman Triathlon (Breakfast/ Lunch/ Dinner/ Snacks/ Fluids)

Monday: 6.00: 80g Corn Flakes + 250ml of Semi-skimmed milk/ 11.10: 135g tuna + 200g pasta/ 20.00: 150g Chilli con carne + 150g white rice/ 2x 50g chocolate bar + 8 jaffa cakes/ 1.5L water + 250ml orange juice + 500ml isotonic sports drink

Tuesday: 6.00: 80g Corn Flakes + 250ml of Semi-skimmed milk/ 9.00: 2 slices of white bread + 10g butter+ 20g Ham & salad/ 15.00: Large Jacket potato + 200g Chilli con carne + 50g low fat cheddar cheese/ 2x 50g chocolate bar + 1 banana + 250ml low fat yogurt/ 1.5L water + 3x cups of tea with 2 sugars + 500ml isotonic sports drink

Wednesday: 6.00: 200g omelette + 50g low fat cheddar cheese/ 11.10: 2 Bagels + 150g salmon + 10g low fat mayonnaise + 50g crisps/ 15.00: Large Jacket potato + 300g beans + 50g cheddar cheese/ 2x muesli bar + 200g dark chocolate/ 1.5L water + 250ml orange juice + 500ml isotonic sports drink

Thursday: 6.00: 80g Corn Flakes + 250ml of Semi-skimmed milk/     10.00: French baguette + 20g flavoured chicken + salad/ 19.00: 450g beef stew + 2 slices white bread/ 3x medium banana’s + 6 chocolate biscuits/ 1.5L water + 2x black coffee with 3 sugars + 500ml isotonic sports drink         

Friday: 6.00: 80g Corn Flakes + 250ml of Semi-skimmed milk/ 12:00 450g beef lasagne/ 21.00: 400g tuna pasta bake + 50g low fat cheddar cheese/ 1 large slice of apple pie + 100g custard/ 1.5L water + 250ml orange juice + 500ml isotonic sports drink     

Saturday: 6.00: 80g Corn Flakes + 250ml of Semi-skimmed milk/     10.00: 300g chicken + sweet & sour source + 200g white rice/ 19.00: 450g chicken & vegetable stir fry + 200g noodles/ 2x English muffins + 2x apple/ 1.5L water + 250ml orange juice + 500ml isotonic sports drink

Sunday: 9.00: 100g Swiss Muesli + 300ml semi-skimmed milk + 30g unsalted nuts/ 12.00: 12inch pizza/ 6.00: 300g white rice + 100g chicken curry/ 2x 50g chocolate bar/ 1.5L water + 3x cups of tea with 2 sugars

This table provides dietary recommendations which Fred may follow in order to sustain his high glycogen stores, intake suitable amounts of protein for growth & repair, adequate amounts of fluids and electrolytes to prevent dehydration & hyponatremia, and also the variations in meals will help prevent taste fatigue.


LAURSEN, Paul B & RHODES, Edward C (2001). Factors Affecting Performance in an Ultraendurance Triathlon. Sports Medicine, 31(3), 197-199.

JEUKENDRUP, Asker E, JENTJENS, Roy & MOSLEY, Luke (2005) Nutritional Considerations in Triathlon. Sports Medicine, 35(2), 165-166.

HUTCHISON, Jennifer (2008) Power of Protein

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