Factors Affecting Performance HSC Core 2

How can nutrition and recovery strategies affect performance?

Syllabus Content STUDENTS LEARN ABOUT Nutritional considerations Pre-performance, including carbohydrate loading During performance Post performance STUDENTS LEARN TO: Compare the dietary requirements of athletes in different sports considering pre, during and post performance needs

Pre-Peformance:The training diet The aim of the training diet is to achieve adequate nutrition to support training and body composition goals. Food consumption needs to take into consideration the type of food consumed (food and drinks) and being aware of the most appropriate time for food.

Carbohydrates are a key fuel source for exercise, especially for prolonged and high intensity exercise. Food = fuel for exercise while fluid = cooling heated muscles, preventing dehydration. If athletes diets do not provide adequate energy and CHO this can lead to fatigue, inability to improve in training, poor concentration during training, reduced immune system functioning and increased susceptibility to injury.

Pre-performance: Eating before exercise Consuming food and fluid before exercise should be seen as an opportunity to fine-tune carbohydrate and fluid levels and to ensure you feel comfortable and confident.  When should I eat? A general guide is to have a meal about 3-4 hours before exercise or a lighter snack about 1-2 hours before exercise. Food requires adequate time to be digested. Athletes need to experiment to find the timing, amount and make up that best suits their individual needs. What should I eat? Food eaten before exercise should provide carbohydrate.  It should also be low in fat and moderate in fibre to make digestion easier and reduce the risk of gastrointestinal discomfort. For most exercise sessions, the emphasis on carbohydrate and fluid for the pre-event meal.

crumpets with jam or honey + flavoured milk   The following foods are suitable to eat 3-4 hours before exercise: crumpets with jam or honey + flavoured milk 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 1-2 hours before exercise: liquid meal supplement milk shake or fruit smoothie sports bars (check labels for carbohydrate and protein content) cereal bars fruit-flavoured yoghurt fruit   The following foods are suitable to eat if there is less than 1 hour before exercise*: sports drink carbohydrate gel cordial sports bars jelly lollies * A small number of people experience an extreme reaction following the intake of carbohydrate in the hour prior to exercise. 

Carbohydrate Loading What is carbohydrate loading? Carbohydrate loading is a strategy involving changes to training and nutrition that can maximise muscle glycogen (carbohydrate) stores prior to endurance competition.  The technique was originally developed in the late 1960's and typically involved a 3-4 day 'depletion phase' involving 3-4 days of hard training plus a low carbohydrate diet. This depletion phase was thought to be necessary to stimulate the enzyme glycogen synthase. This was then followed immediately by a 3-4 day 'loading phase' involving rest combined with a high carbohydrate diet. The combination of the two phases was shown to boost muscle carbohydrate stores beyond their usual resting levels. Ongoing research has allowed the method to be refined so that modern day carbohydrate loading is now more manageable for athletes. The depletion phase was demonstrated to be no longer necessary, which is a bonus for athletes as this phase was very difficult. Australian marathon runner, Steve Moneghetti has described the depletion phase as making him feel like "death warmed up". Today, 1-4 days of exercise taper while following a high carbohydrate diet (7-12g/kg body weight) is sufficient to elevate muscle glycogen levels.

Does carbohydrate loading improve performance? Muscle glycogen levels are normally in the range of 100-120 mmol/kg ww (wet weight).  Carbohydrate loading enables muscle glycogen levels to be increased to around 150-200 mmol/kg ww.  This extra supply of carbohydrate has been demonstrated to improve endurance exercise by allowing athletes to exercise at their optimal pace for a longer time.  It is estimated that carbohydrate loading can improve performance over a set distance by 2-3%.

A trained athlete is much more efficient at storing carbohydrates than the normal population. Replenishment rates are also higher immediately after exercise. If an athlete has less than the suggested carbohydrate intake, this will cause glycogen stores to be depleted and performance will be diminished. Prior to competition, it is advised that an athlete allow 3-4 hours for a large sized carbohydrate meal and less than two hours for a light meal or snack.

Who should carbohydrate load? Anyone exercising continuously at a moderate to high intensity for 90 minutes or longer is likely to benefit from carbohydrate loading.  Typically, sports such as cycling, marathon running, longer distance triathlon, cross-country skiing and endurance swimming benefit from carbohydrate loading.  Shorter-term exercise is unlikely to benefit as the body's usual carbohydrate stores are adequate.   Carbohydrate loading is generally not practical to achieve in team sports where games are played every 3-4 days.  Although it might be argued that players in football and AFL have heavy demands on their muscle fuel stores, it may not be possible to achieve a full carbohydrate loading protocol within the weekly schedule of training and games.

During Performance The goal of nutrition intake during exercise is to minimise the fluid deficit and, in the case of exercise of moderate to high intensity lasting longer than 60 minutes, provide an additional fuel source for the muscle and central nervous system Intake of carbohydrate during exercise provides an additional fuel source and has the potential to improve exercise capacity in situations where muscle or liver glycogen stores may limit performance. Research shows it is beneficial to athletes competing in individual and team based sports of an intermittent nature lasting longer than 60 minutes.

Depending on the nature of the event, suitable carbohydrate rich food and fluid options may include bananas, sports gels/bars and sports drinks. The latter has the advantage of helping the athlete meet his or her fuel and fluid demands simultaneously. Dehydration to the extent of just 2% of an athletes starting body weight can have detrimental effects on performance, which include: Reduced aerobic performance Increased perceived exertion Reduced mental function Slowed gastric emptying- resulting in stomach discomfort Athletes should look for opportunities to consume fluids during their sport to maximise hydration and performance.

CHO Recommendations during exercise

Post Performance After extensive performance glycogen levels in both the liver and muscle are depleted. For the athlete’s recovery and preparation for the next performance, it is important that the body is returned to its normal state as quickly as possible. This is best achieved through proactive recovery. Proactive recovery places great emphasis on immediately refueling and rehydration that continues until a pre-event state is obtained.

Proactive recovery begins immediately after and continues for 8-12 hours following performance. This enables optimisation of body repair and regeneration process. Research suggests that following endurance based activity, a carbohydrate intake of 50-100 grams in the first two hours is highly beneficial. This initial intake is then followed by intakes of 50-75 grams every two hours until a total of 500-600 grams of carbohydrates has been consumed.

The best way to recover is to act quickly and eat food with high carbohydrate content. This is best achieved through: Immediately replacing depleted muscle and liver glycogen stores – this includes an intake high in carbohydrates and inclusive of food and drinks with a high GI (high spike in insulin) Rehydration to replace fluid and electrolytes lost during the event (water/carbohydrate solutions of 5-8%) in quantities larger than normal Active rest to enhance the manufacturing of red blood cells and new proteins. Additional information can be found at the following website: http://www.ausport.gov.au/ais/nutrition/factsheets/competition_and_training/recovery_nutrition