Nutrition and Hydration

15 04 IRON.pdf - Information on iron

15 04 sport drinks.pdf - Information on sports drinks

 

NUTRITION

For the human body to perform in the pool, it needs energy and this energy comes from the food we eat. An adequate, nutritious, balanced diet avoids the need for supplements, delays the onset of fatigue while aiding recovery from training and performance.

The general population should be eating foods which have a Low Glycemic Index, foods which are closest to their naturally found state (minimal processing) and avoid consuming refined fatty foods. To make sure that we are getting enough vitamins and minerals in our diet, our plates should include foods of many different colours.

For more information on the Glycemic Index please visit Sydney Universities site: http://www.glycemicindex.com/

Athletes expel more energy (kilojoules) than the general population, so their diets should be adjusted accordingly. On training days they need a to have a higher carbohydrate intake.

 

Carbohydrates

Carbs are found in foods as either sugars or starch. Carbs are broken down into glucose (or blood sugar) - a process called glycolysis. Starches and complex carbohydrates are broken down into glycogen which is stored in the liver and muscles. Muscle Glycogen is broken down to provide energy (adenosine triphosphate - see below) for both aerobic activity and anaerobic activity. Carbohydrate contains 16 kilojoules per gram.

Carbohydrate loading is a strategy used to maximise muscle glycogen stores prior to endurance competition. In the last 3 days prior to competition the diet is increased to 70-80% Carbohydrates and training is reduced.

 

Fats

Dietary fats are found in the blood as free fatty acids and triglycerides. Excess fat is stored as triglyceride in cells called adipose tissue. During aerobic activity these fats are called upon and through a cycle of reactions break down into ATP. Fat contains 37 kilojoules per gram.

 

Proteins

Proteins form amino acids, the building blocks of all cells in the body. During normal circumstances protein plays no role in providing ATP, but can be used as a fuel source under extreme conditions. protein contains 17 kilojoules per gram.

It has been found to beneficial and is recommended that athletes ingest protein (food or drink) within the first 15 minutes of training, so that muscles can begin repairing themselves straight away.

 

Diets for Swimmers

For information on Diets for swimming download the Sports Dietitians Australia Swimming Fact Sheet:http://www.sportsdietitians.com.au/content/177/Swimming/

 

Iron Deficiency - a Common Problem, especially in Female Athletes

Female athletes are often anaemic. Iron is essential for athletic performance, carrying oxygen to and carbon dioxide away from all the cells in the body. An increase in iron is needed when in hard training, for red blood cells and blood vessel production. Low iron levels effect concentration and lower the immune system. Athletes who eat little or no red meat have difficulty meeting the bodies iron needs. Swimmers who are showing symptoms of an iron deficiency (such as fatigue and weakness) can see their doctor for a blood test.

For more information on Iron Deficiency download the Sports Dietitians Australia Swimming Fact Sheet:http://www.sportsdietitians.com.au/content/177/Swimming/

 

HYDRATION

Keeping up our fluid intake is very important, but easy to forget. Dehydration has a detrimental effect on performance and can be a greater limiting factor than diet, rest and fitness. Bringing a drink bottle to the gym, to pool sessions and to competitions is as essential as packing a cossies, caps and goggles. Why? When we swim, we sweat. Our bodies loose water which must be replaced.

Parents may be able to recall images from the 1984 Olympic Games, of wobbly marathon runners crawling to the finish line. That's the extreme effect of failing to adequately replace fluids lost through sweating. When your bodies fluid levels drop below normal, your heart has to work harder to pump out the same amount of blood. Dehydration also eats away at skill levels and concentration.

Swimmers can weigh themselves before training, measure their fluid intake during training, and then weigh themselves after training once dry. If the swimmer has lost weight, they need to increase the amount of water they consume. Any loss in weight (grams) equals the loss of water in your body (milliliters). For every liter loss 1.5 liters should be replaced.

Remember drink bottles should be taken to carnivals. Regular drinking before and after warm ups, races and swim downs is advisable. If swimmers wait until they are thirsty to drink, it can be too late.

For more information on Hydration download the Sports Dietitians Australia Swimming Fact Sheet:http://www.sportsdietitians.com.au/content/177/Swimming/

 

PHYSIOLOGY

In the human body energy is needed for:

Energy comes in different forms including chemical, electrical, heat, mechanical, nuclear energy & sunlight. The two main forms of energy important for movement are:

When we move or exercise chemical energy in the form of food is transferred into mechanical energy in the form of movement. Heat energy is a by-product of this conversion.

There are four basic energy compounds in the body; the primary energy compound adenosine triphosphate (ATP), and the three secondary compounds of creatine phosphate (CP), glycogen (carbohydrate) and fat.

Our bodies breaks down food in the form of carbohydrates, fats and protein to produce ATP, the mechanical energy required for muscle contraction.

Muscles store a small amount of ATP, ready to carry out explosive sprinting. In sports that have repeated muscle contraction such as swimming, the supply of ATP must be constantly replenished from other fuel sources.

Initial energy (eg. energy used to dive at the beginning of a race) may be obtained from substances already in the muscle, without the need for oxygen (anaerobic). The anaerobic energy is produced from high-energy phosphate substances (phosphate energy system) or from carbohydrate stores (lactic energy system).

So in other words food provides energy in the form of chemical energy, which is converted to mechanical energy. The breakdown of food produces energy that is stored in the body for later use.

 

At the Molecular Level

As the body uses ATP it produces more - metabolism. The ATP molecule is made up of a large molecule called an Adenosine molecule and three smaller molecules called phosphates. When one of the phosphate molecules breaks away from the ATP molecule (creating energy) a double phosphate molecule called Adenosine Diphosphate (ADP) is formed, along with a single molecule - Adenozine Monophosphate (AMP).

So ATP is broken down into ADP and energy, and is then re-synthesized by enzymes through two reactions:

  1. The reaction between ADP and CP which produces creatine, ATP and more energy.
  2. The reaction between ADP and ADP which produces AMP and ATP

 

The Energy Systems During a Race & Training (Pubescents and Adults)

The supplies of the phosphate energy system last 5-10 seconds and are used up in the first 25m of a race. If the swimmers rests after an effort the energy stores will be rebuilt by 50% after 30 seconds and 100% after 2-3 minutes.

At maximum levels of effort the amount of ATP present in muscle is sufficient for only 1 second of exercise and the phosphate energy system in total will last 5 seconds. Lactic acid will already be produced at 10 seconds, and will reach peak volumes quickly, forcing exercise to cease.

In all swimming events the anaerobic supply is depleted and the energy source has to come from elsewhere . . . the lactic energy system. Energy is now provided from glycogen stored in the active muscle. As well as producing ATP, glycogen produces Pyruvate, which is further broken down into ATP and lactic acid. This production of lactic acid is said to give the feeling of fatigue.

Continuous activity, which leads to exhaustion 45-60 seconds, results in maximal values for lactic accumulation. There is a given level of effort where energy demands will be unable to be met from aerobic energy release alone, and lactic acid will be produced. Exercise done at a higher intensity than this is limited by lactic accumulation.

 

Recovery / Swim down

Lactic Acid requires up to 45-60 minutes to be completely removed. For senior swimmers it is important to spread out tough events on race day which have significant lactate production and tolerance eg. 100 & 200 BF. Lactic Acid is removed more quickly if the swimmer continues some light exercise rather than resting completely. It has been found that swimmers should do swim downs with a minimum of 800m.

eg. 200 FS HR 40 bbm, 4 x 50 K exp. 1st 15, 4 x 50 S exp. 1st 15, 200 E BK

 

The Importance of Aerobic Fitness

During longer evens and efforts oxygen is the the predominate supplier of ATP for continual muscle contraction. Oxygen is used to release energy from glycogen and fat stores. The athletes ability to transport and utilise oxygen becomes a more limiting factor to performance, the longer the event is.

So it is important to have high stores of carbohydrates before training and competition, so performance isn't reduced. Exercise supported by aerobic metabolism (oxidation of carbohydrates and fat fuel stores) is 13 times more efficient as anaerobic activity.

Improved cardiovascular function will mean the body will be able to transport blood more efficiently, allowing the body to supply oxygen and nutrients to the muscle cells, and remove lactic acid more quickly. Vascular development equals quicker recovery time for swimmers!

 

 

 

 

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