Optimum sporting performance requires sufficient preparation both physical and psychological, adequate rest and recovery and the most suitable nutrition for your particular sport. In all cases the main focus will be on the timing and size of meals while the nutrients of most concern will be carbohydrates and fats for energy production, protein for muscle growth, tissue repair and to a lesser degree energy production, water and electrolytes (sodium and potassium). Training and competing at a high level places very great demands on your body which need to be met by proper nutrition otherwise you may experience loss of form, ill health, tiredness, weight loss, loss of mental toughness, injuries etc. Athletes have a variety of choices when it comes to nutritional sources;
(Premier Training) Meals are typically categorized as pre-training, during training and post-training. Other areas of sports nutrition you may need to consider are hydration, carbohydrate loading, gastric emptying and nutrient absorption |
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The graph above is a representation of meal timing prior to a one hour training session at 1pm. A meal high in complex carbohydrates should be consumed 2 – 3 hours before the training session. Some authorities recommend that the meal should have a high percentage of low Glycaemic Index (GI) foods with a high Glycaemic Load (GL) however studies have shown that there is little difference in the performance of athletes on a low or high GI pre-training meal and that the greatest benefit is derived from the carbohydrates consumed during training / competition. Various studies have shown that refuelling during training / competition is acceptable if;
Isotonic drinks can delay the onset of muscular and mental fatigue and improve the performance of endurance athletes. They also replace lost fluid and essential salts and provide energy and are absorbed into the body at the same rate as water. Many commercially produced isotonic drinks have undesirable additives and can be expensive. Two simple home made alternatives are;
Hypotonic drinks are an alternative and are absorbed into the body faster than water but are best used during severe dehydration in the absence of an intravenous drip. * the addition of a small amount of natural (sea) salt helps with fluid absorption. The principle aim is to replenish glycogen stores (glycogen having been used as energy to exercise – the more intense the training session the more glycogen that is used and therefore depleted). This is particularly important if training is to be pursued the following day. One of the best ways is to consume 50g of complex carbohydrates straight after training, then a further 50g of carbohydrates every ½ hour over a 2 hour period (see table below). Alternatively the meals should contain 1g of complex carbohydrate per kg of body weight, consumed every two hours. The first intake should be 30 mins post training with an intake over 24 hours of 7- 10g per kg of body weight (Burke & Deakin, 2000). High GI foods should be consumed since the muscles are more sensitive to the effects of insulin straight after training allowing rapid resynthesis of muscle glycogen stores. |
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During training and competition the majority of fluid lost will be in the form of sweat as this is part of the body’s natural cooling mechanism. Sweat is 99% water and 1% salts (sodium and potassium) which needs to be replaced and the amount of sweat produced is affected by temperature, genetics, altitude, acclimatisation, respiration rate and the amount of fluid already in the body. To determine how much water you need to consume after training, weigh before and after your training session. Any loss of weight will be loss of water with each kg equating to 1 litre of water. Be aware though that a high proportion of your sweat will still be in your clothes therefore when you weigh yourself do so with minimal clothing both before and after the event / training session. Another indicator is urine colour. If it is dark like apple juice you are dehydrated while if it is like pale lemon juice you are well hydrated. To reduce the risk of becoming dehydrated it is very important to drink small amounts of fluids (mainly pure water) during the hours leading up to your event and during the event (every 15 to 30 minutes). Researchers have found that sports drinks containing between 6% and 8% carbohydrate (sugars) are absorbed into the body as rapidly as water and can provide energy to working muscles that water cannot. These are known as isotonic drinks. This extra energy can delay fatigue and possibly improve performance, particularly if the sport lasts longer than 1 hour. If you drink a sports drink, you can maintain your blood sugar level even when the sugar stored in your muscles (glycogen) is running low. This allows your body to continue to produce energy at a high rate. Drinks containing less than 5% carbohydrate do not provide enough energy to improve your performance. So, athletes who dilute sports drink are most likely not getting enough energy from their drink to maintain a good blood sugar level. Drinking beverages that exceed a 10% carbohydrate level (most fizzy drinks and some fruit juices) often have negative side effects such as abdominal cramps, nausea, and diarrhea and can harm your performance. In order to calculate the percentage of carbohydrates in your sports drinks do the following calculation; Carbohydrates per serving (g) / serving size (ml) x 100 = % carbohydrate in your drink. For example a drink that contains 30g of carbohydrates per 300ml serving has a concentration of 30g / 300ml x 100 = 10%. Most drinks will include details as to the amount of carbohydrates (and other nutrients) it contains per serving or per 100ml. Did you know? 2% water (weight) loss during sports will noticeably reduce your performance Protein (powders) drinks In addition to replenishing glycogen stores and lost electrolytes it is important to increase your protein intake to repair tissue that inevitably becomes damaged with intense training and to encourage muscle growth. Perhaps the most common way is via the consumption of protein shakes which come in a wide variety of forms and are promoted widely amongst the body building fraternity. Currently the best source is whey protein. Whey is the liquid by-product of cheese production and in its natural form is the most useful protein to the body. However the manufacturing process that turns it into powder can render it less useful than in its original form. The whey liquid is dried often at high temperatures for speed of manufacture (above 60ºC) however this destroys some of the protein. Whey powder manufactured / dried at low temperatures (below 50ºC) are the best choice (read the label) to ensure good quality, useful protein. Other factors that affect the value of protein powders are the additives that are used to change its colour and flavour and the absence of fat. Fat (lipids) are required for proper metabolism (use) of protein therefore be aware that if it is not present in the powder you need to consume it separately e.g. mix the powder with whole organic milk. In order to benefit from this manufactured protein it must contain the Branched Chain Amino Acids (BCAA) L-leucine, L-isoleucine and L-valine. BCAA make up about 1/3 of skeletal muscle and are essential for protein synthesis (the formation of protein). They also significantly increase the production of insulin which plays a role in muscle development. BCAA taken pre-workout has been shown to reduce catabolism (muscle breakdown) brought on by intense resistance training while BCAA taken post-workout has been shown to greatly enhance anabolism (muscle growth). Do remember that like vitamin supplements, protein powders are just that….supplements and as such are not designed to replace a healthy balanced meal. In the Protein section you will see what the average protein requirements are and providing you are not vegan or vegetarian or involved in daily intense training you are probably already consuming suffieicent protein. Excess protein not used for cell repair, muscle growth, production of hormones etc. will be converted to fat and reslts in an increase in nitrogen that needs to be removed from the body. |
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The aim of carbohydrate loading is to increase the amount of glycogen stored in the muscles and liver. Its greatest use is to endurance athletes who need to call upon their glycogen stores when fat no longer provides sufficient energy for their needs. One method is to manipulate the diet and training intensity to ensure the muscles and liver are depleted of glycogen as much as possible, then to impose a period or rest during which the muscles and liver naturally increase their glycogen storage capacity. During this period of rest high quantities of carbohydrates are then consumed. A more favoured method is to maintain a high carbohydrate diet but to reduce the intensity of the training sessions as the event approaches so as not to deplete carbohydrate store but to maintain it. This method works better for a wider cross section of sports especially those that occur frequently e.g. football, rugby, netball etc since the athlete can continue to train without enduring an unproductive period of rest. |
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Manipulating the diet and training intensity |
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Reducing intensity while maintaining a high carbohydrate intake |
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Despite the benefits of carbohydrate loading, research has shown that the greatest benefits to performance in sports of long duration (in excess of 90 minutes) are derived from the during competition meal i.e. isotonic sports drinks. There is a limit to the amount of glycogen that can be stored in the muscles and liver and during endurance events these stores will eventually start to deplete therefore toping up during the event will enable you to continue. How quickly this additional energy source will be made available to your muscles depends mainly on the rate of gastric emptying and the rate of nutrient absorption. Gastric Emptying (GE) is the emptying of the contents of the stomach into the small intestines. The G.E. rate of liquids is affected by a number of factors including;
Nutrient Absorption occurs when the ingested food is in the small intestines. The nutrients (carbohydrates, proteins, vitamins and minerals) are absorbed through the intestinal walls (fats via the lymphatic system) into the blood stream and directed to the liver. The rate of fluid absorption is affected by;
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The Sports Injuries & Fitness Clinic
