This is a two part series on nutrition; Part 1 covers the basics and Carbohydrate Loading, Part 2 will cover Race Day Nutrition, Forms & Methods of Ingestion and Sources.
Nutrition should be an integral part of any triathletes’ program, nutrients provided by food and supplements provide the energy required to train, race and recover. Carbohydrates (CHO) are our main fuel source, and replenishing these stores becomes both more important and more systematic (re timing and composition) as the demands of training increase; – the pinnacle being able to adequately manage fuel stores in long course racing (Ironman and Half Ironman distance events). The timing, composition and amount of fuel that is consumed becomes critical when striving for the best results.
The Basics – fuelling for training and recovery
CHO based foods can be broken down into High GI (glycaemic index) and Low GI. High GI foods cause a brief, rapid rise in blood glucose, whereas low GI foods cause a slower, sustained release of glucose to the blood.
Food consumed before exercise is only useful once it has been digested and absorbed. This means you need to time your food intake so that the fuel becomes available during the exercise period. Generally, foods higher in fat, protein and fibre tend to take longer to digest than other foods, and may increase the risk of stomach discomfort during exercise. Further to this, food is better tolerated during lower intensity activities, such as cycling, especially compared to running (where ground impact causes jostling of the gut). This is a critical point in terms of fuelling for triathlon. Below is a general guide for pre-exercise fuel consumption:
Low GI carbohydrates, low fat, moderate protein 3-4 hrs prior to competition
Mixed GI carbohydrates, low fat, low protein 1-2 hrs prior
High/er GI carbohydrates, sports bars, gels, sports drinks <1hr prior
It is important to plan daily food intake around training – consumption of meals and snacks are a vital part of recovery between sessions. During recovery you should aim to restore expended fuel, fluids, minerals and electrolytes, as well as, repair immune function and cell damage. The first 30min post exercise is crucial; consume at least 1g of CHO per kilogram of bodyweight.
Research shows that consuming high CHO foods with a small amount of protein aides absorption of the CHO, repair of muscle tissue, and helps the proteins used to metabolise fuel during exercise.
Here are some examples of good recovery snacks:
250-300ml milk shake or fruit smoothie
600ml low fat flavoured milk
1-2 sports bars (check labels for carbohydrate and protein content)
1 large bowl (2 cups) breakfast cereal with milk
1 large or 2 small cereal bars + 200g carton fruit-flavoured yoghurt
220g baked beans on 2 slices of toast
1 bread roll with cheese/meat filling + large banana
Effective hydration is another variable that should be addressed. Dehydration impairs the body’s ability to thermoregulate (maintain body temperature). Impaired thermoregulation will contribute to slow gastric emptying, reduced skin blood flow, accelerated glycolysis, and subsequent fatigue (central and peripheral). Heat stroke is of the greatest concern in this case. Individual hydration needs vary enormously, but can be easily monitored by simple and sophisticated methods. Consider monitoring body weight and urine specific gravity.
Fluid intake is enhanced when beverages are cool, flavoured and contains sodium (sports drinks); you should choose a sports drink which has 6-8% carbohydrate, and around 20mmol/L sodium, such as Gatorade.
If well hydrated leading into event, 4ml per kilogram of body weight 30min prior, and 2ml per kilogram of bodyweight every 10min during the event works well. During the recovery phase fluids should be replaced at 150% of their deficit.
Leading in to race day – the 36hrs prior to an event, Carbohydrate Loading Phase
Carbohydrate loading enables muscle glycogen levels to be increased, previously demonstrated to improve performance over long distances (>90min) by 2-3%. The current preferred method involves an exercise taper (4-7 days) combined with high CHO intake (7-12g/kg body weight) in the 24-48hrs leading into an event. This has been shown as sufficient to elevate muscle and liver glycogen levels. For most effective results it is recommended that you reduce foods high in fibre and fat.
Some studies have suggested that females may be less responsive to carbohydrate loading, especially during the follicular phase of the menstrual cycle. This appears to be, at least partly, because they have difficulty consuming the larger amounts of carbohydrate required for a complete CHO load.
If you are racing short course events, you should combine the taper period with a CHO intake of 7-8 g of carbohydrate per kilogram body weight for 24 hours before competition to adequately increase muscle glycogen stores. However, if you’re competing in half ironman, long course and ironman races you should increase your carbohydrate intake to 10-12 g of carbohydrate per kilogram body weight for 48-72 hours before the race start.