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Nutritional Considerations

Pre-performance

The training diet

The aim of the training diet is to achieve nutritional adequacy (providing the body with recommended intake of vitamins and minerals) and provide appropriate amounts of energy to support training and body composition goals. It is important that nutritional targets for athletes (such as total energy, protein and carbohydrate requirements) are based on an individual athlete’s goal body weight and muscle mass, as this provides more specific targets.

Carbohydrates (starches and sugars) are a key fuel source for exercise, especially during prolonged and high-intensity exercise. The body stores carbohydrate as glycogen in the skeletal muscles and liver; however, its storage capacity is limited. If athletes are not able to consistently provide adequate energy and carbohydrates in their training diet, this can lead to fatigue, inability to improve in training, poor concentration during training sessions, reduced immune system functioning and increased susceptibility to injury.

The amount of carbohydrate needed depends on the fuel needs of the athlete’s training program, including the frequency, duration and intensity of the training. Training sessions and activity levels change from day to day, and carbohydrate intake needs to be adjusted to reflect this. On high-activity days, carbohydrate intake should be increased to provide the required fuel for the extra activity and promote recovery between sessions. Alternatively, on low- or no-training days, carbohydrate intake should be reduced to reflect the decreased training load.

The pre-event meal

The aim of the pre-event meal is to ensure the athlete’s glycogen stores are topped up and they are well hydrated. Establishing a good pre-event meal, which provides the right nutrients and fluids, provides psychological benefits for athletes as they know they have prepared well. This meal should be high in carbohydrates, moderate in protein and low in fibre and fats. Meals high in fibre and fat take longer to digest, and therefore can lead to stomach discomfort during exercise.

Key considerations for the pre-event meal include:

• What is the duration and intensity of the event?

• How long has it been since the last meal or snack?

• How long is it until the event starts?

The following foods are suitable to eat three to four hours before exercise:

• crumpets with jam or honey + flavoured milk

• Pancakes with honey or maple syrup

• baked potato + cottage cheese filling + glass of milk

• baked beans on toast

• breakfast cereal with milk

• bread roll with cheese/meat filling + banana

• fruit salad with fruit-flavoured yoghurt

• pasta or rice with a sauce based on low-fat

ingredients (e.g. tomato, vegetables, lean meat).

The following snacks are suitable to eat one to two hours before exercise:

• liquid meal supplement

• milkshake or fruit smoothie

• sports bars (check labels for carbohydrate and protein content)

• low-fibre breakfast cereal (rice bubbles/ cornflakes) with milk

• cereal bars

• fruit-flavoured yoghurt

• fruit.

Source: Adapted from AIS, ‘Eating before exercise fact sheet’

Some of the glycogen stores in the liver are released overnight to provide glucose for the brain, as the brain remains quite active during sleep. Athletes who compete in events that have early morning starts (such as some triathlons or endurance events) need to be aware of this, and develop a nutritional plan such as getting up extra early to ensure they have time for an adequate breakfast or planning a high-carbohydrate snack within one to two hours of the event starting time. This enables them to top up the glycogen losses in the liver that occur during an overnight fast.

Hydration before the event needs to be planned carefully, and should start many hours before the event commences. As a guide, athletes should include 300–600 millilitres of fluid with the pre-event meal and another 300–400 millilitres approximately 20 minutes before the event, allowing enough time for a toilet stop if needed. Fluids should also be sipped regularly between the pre-event meal and the starting time, and using fluids that contain sodium will help fluid absorption. It is important for athletes to keep a drink bottle with them to help prompt them to consume enough fluid, as many athletes forget to hydrate well due to nerves, organising equipment or going over tactics/race strategy with coaches.

Carbohydrate loading

Carbohydrate loading refers to strategies that aim to maximise muscle glycogen stores prior to a competitive event (high carbohydrate intake combined with light training or rest). For events lasting for less than 60 minutes, there is no performance benefit associated with carbohydrate loading, and it may actually have a negative effect on performance in short-duration events at high intensity. Provided the athlete has only engaged in light exercise or rested for the 24–36 hours prior to the event, adequate glycogen stores will be achieved with an intake of around 5 grams of carbohydrate per kilogram of body weight over this period.

For endurance events lasting more than 90 minutes, such as marathons, triathlons, long- distance swimming, cross-country skiing and road race cycling, effective carbohydrate loading can improve overall performance by 2–3 per cent. Traditional carbohydrate loading protocols consisted of a three- to four-day ‘depletion phase’ involving hard training and a low-carbohydrate diet, followed by a three- to four-day ‘loading phase’, which involved tapered training and a high-carbohydrate diet. More recent studies have shown that glycogen stores can be increased to the same levels by following a high-carbohydrate diet for 36–48 hours while the athlete is rested. The recommended carbohydrate intake to achieve effective carbohydrate loading is 8–12 grams per kilogram of body weight.

It is important that athletes plan their food and fluid intake carefully to meet these carbohydrate targets during exercise. In endurance events, where a consistent carbohydrate intake is needed over many hours, it is important to think about the type of carbohydrate the athlete is going to consume. Repeatedly having the same type of sugars from sports drinks or energy gels can cause athletes to experience symptoms such as stomach cramps, bloating, the need to go to the toilet and potentially diarrhoea. A combination of ‘sports foods’ (such as gels and sports drinks) and real foods (fruit, muesli/sports bars, low-fibre sandwiches) is best tolerated.

During performance

The most important factor when considering whether carbohydrate intake during exercise will improve performance is the duration of the exercise. The following table summarises the amount of carbohydrate recommended during exercise. It is important that athletes plan their food and fluid intake carefully to meet these carbohydrate targets during exercise. In endurance events, where a consistent carbohydrate intake is needed over many hours, it is important to think about the type of carbohydrate the athlete is going to consume. Repeatedly having the same type of sugars from sports drinks or energy gels can cause athletes to experience symptoms such as stomach cramps, bloating, the need to go to the toilet and potentially diarrhoea. A combination of ‘sports foods’ (such as gels and sports drinks) and real foods (fruit, muesli/sports bars, low-fibre sandwiches) is best tolerated. Another benefit of using a mix of sports foods and real foods is that the foods the athlete eats during the event can also be a good source of key electrolytes such as sodium, potassium and magnesium to help with hydration. It is important that athletes carefully plan their food and fluid intake according to the event, and identify where their opportunities to eat and drink will occur. Consider a triathlon, for example. There is no opportunity for athletes to carry or consume food during the swim leg. There is also a better opportunity for athletes to carry more food and eat on the bike than during the run leg.

Fluid

It is important that athletes are educated about hydration, and that any fluids provided to athletes are cool, palatable and conveniently available, or they will not be consumed. Research has shown that athletes typically only replace 30–70 per cent of sweat lost during exercise.

Fluid requirements vary significantly between athletes and between exercise situations. Fluid losses are affected by:

• genetics – some people sweat more than others

• body size – larger athletes tend to sweat more than smaller athletes

• fitness – fitter people sweat earlier in exercise and in larger volumes

• environment – sweat losses are higher in hot, humid conditions

• exercise intensity – sweat losses increase as exercise intensity increases.

When planning for an endurance event, athletes should carefully monitor their fluid intake during training and try to simulate race conditions (intensity, duration and environmental conditions) where possible. Negative effects on performance start to occur at just 2 per cent dehydration, so athletes should aim to keep their fluid losses to less than this. The potential effects of mild dehydration include:

• reduced mental function leading to poor concentration

• increased ratings of perceived exertion leading to feelings of fatigue at lower intensity

• delayed gastric emptying from the stomach leading to stomach discomfort

• poor aerobic performance

• impaired heat regulation.

By recording body weight immediately before and after exercise (with minimal clothing, if any) athletes will get a reasonably accurate idea of their fluid losses as 1 kilogram loss in weight reflects approximately 1 litre fluid loss.

For example, if an athlete weighs 70 kilograms before exercise and 68 kilograms after, the 2 kilogram loss of weight reflects their overall fluid losses over that exercise session (a 2.9 per cent

Over-hydrating

Consuming fluid in excess of requirements may cause some gastrointestinal discomfort, and can lead to hyponatraemia (low blood sodium levels), which causes symptoms similar to dehydration and is potentially life threatening. Hyponatraemia is unlikely to occur in events of less than two or three hours’ duration, and athletes are at risk when large volumes of low-sodium drinks (such as water) are consumed when sweat losses are small. Those most susceptible to hyponatraemia are small females who have long race times (more than three or four hours), as these athletes tend to have relatively small sweat losses and plenty of time to consume large amounts of fluid during the event. As a result, structured hydration plans are often not advisable for these athletes. The best way to prevent hyponatraemia is to focus on consuming sodium- containing fluids such as sports drink and sodium-containing foods such as vegemite sandwiches, as well as limiting fluid intake to no more than sweat loss.

It is very important that athletes train their diets to make sure the foods and drinks they plan to have during the event are well tolerated and don’t result in any stomach upset, as this can significantly affect performance and may result in the athlete not even finishing the race. The general advice is not to try anything new on event day.

Post-performance

Recovery nutrition has received much attention, and has been heavily researched in recent decades. Immediately following exercise, the activity of enzymes involved in refuelling (synthesis and storing glycogen) and repairing (repair of damaged muscle tissue and building of new muscle tissue) is increased significantly. Therefore, the aim of the recovery meal/snack is to provide carbohydrates to refuel and protein to repair muscle tissue as well as fluid to correct any dehydration.

Athletes are encouraged to consume foods and drinks that provide 1–1.2 grams of carbohydrate per kilogram of body weight within the first hour of finishing, as this is when rates of glycogen synthesis are greatest. This is especially important if the time between prolonged training sessions is less than eight hours. High glycaemic index carbohydrate foods have been shown to refuel muscle and liver glycogen stores more quickly, and these should be the basis of the carbohydrate consumed within the first hour. This meal should also be low in fibre, as this will slow the digestion and absorption of carbohydrate. Conveniently, the majority of high glycaemic carbohydrates are low in fibre.

A small amount of protein is also important for muscle recovery, especially after high-intensity sports and strength training. Athletes should aim to have approximately 15 grams of protein following high-intensity exercise, and recent research suggests that the optimal amount following strength training and power-based sports is about 300 milligrams of protein per kilogram of ideal body weight (21 grams of protein based on a 70 kilogram athlete).

Examples of low-fibre recovery meals that provide carbohydrate and protein include:

• milkshakes/smoothies

• liquid meal supplements based on milk

• yoghurt and fruit salad

• crumpets/muffins/toast with jam or honey with 300 millilitres of milk

• bowl of low fibre cereal with milk.

After high-intensity exercise, the immune system can be suppressed for many hours. Consuming a suitable recovery meal has been shown to improve the functioning of the immune system, which is important to help prevent athletes catching infectious illnesses.

Do athletes need a post-performance meal?

Athletes need to think practically about their day- to-day training schedules and plan recovery meals accordingly. If athletes have only completed a short training session or trained at a low intensity, then it is highly unlikely that they have completely used their glycogen stores and therefore do not require such a high-carbohydrate recovery meal. If athletes routinely consume more carbohydrate than they need, it may lead to unwanted weight gain, which will hamper performance.

Dietary requirements of athletes in different ports

Different sporting events vary significantly in their intensity and duration, and so do athletes’ nutritional needs in different sports. To highlight the extent of the different fuel needs of different sports, compare cyclists competing in the Tour de France with athletes in low-intensity and short- duration sports such as archery. The energy needs of cyclists in the Tour de France can be as high as 30 000 kilojoules a day on the longer-duration and higher-intensity stages, and average 20 000–25 kilojoules a day over the 21-day event. An archer will not require significantly more energy (or carbohydrate) than their typical daily intake of 8000–10000 kilojoules (depending on gender and normal weight).

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