Athletics Research Reports

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Most of the reports on this page are derived from the newsletter "Peak Performance" (see details on the main athletics page).

I had hoped that this page would be updated monthly once I had caught up with the backlog, more frequently until then. Unfortunately pressure of work and other activities interfered. My apologies for that. I hope to get back on track in the next week or so. Until then, please bear with me and check the page occasionally to see how it's going.

Stitch - cause and cure

Most runners occasionally suffer from that excruciating pain in the side known as stitch. So, apparently, do horse and camel riders, footballers, tennis players and even motorcyclists, but not skaters, cross-country skiers, swimmers or cyclists. The common factor between sufferers is that our internal organs bounce up and down while running, etc. When an organ moves down relative to your body, it pulls on the diaphragm. If the diaphragm is at that moment also moving down,no problem, but if it is moving up then the pull strains the muscle. Repeated strain can cause the muscle to go into spasm, and you feel intense pain. There are a couple of other reasons which sometimes apply (particularly to marathon runners), but the cure given below still works because they are still the result of internal bits and pieces moving up and down to cause trouble.

The reason stitch is sometimes (but not always) associated with eating before the exercise is because a stomach full of food is heavier than normal and therefore causes greater strain on the diaphragm than normal. In reality, the liver is usually by far the heaviest organ and therefore the usual cause of stitch. [Personal note: In any particular case, you can get an idea of which is the cause from which side is affected, the stomach being to the left and the liver to the right.]

The simple cure if you get stitch while running is to change your breathing pattern. Breathing controls the movements of your diaphragm, and almost all runners coordinate their breathing with their striding. If you notice, you will almost certainly find that every time you breathe out it coincides with the same foot hitting the ground (normally the same side as the stitch). To cure a case of stitch, simply change over so you breathe out as the other foot hits the ground. It works amazingly quickly.

This subject is discussed in Peak Performance at great length in issue no 21, published June 1992, together with various methods of prevention. If you want all the detail, the newsletter back number may still be available from the publisher.

Food, supplements, drinks & gadgets

Water
Water fulfils a number of functions in the human body, but two in particular are of outstanding importance when engaging in vigorous exercise of any kind.

One of these is as a major constituent of blood. Too little water in the blood stream means the viscosity of the blood is too high. This makes it difficult for the heart to pump it round the body and so reduces the rate at which fresh energy supplies can reach the muscles, and also the rate at which the blood can reach the skin to be cooled. Furthermore, excessively thick blood makes it more difficult for the exchange of substances between the blood and the muscle to take place. Thus too little water in the blood can seriously reduce the energy available to power the legs, causing the runner to slow down drastically.

The second major function is to supply the sweat needed to cool the body. Whenever vigorous exercise is undertaken, the body produces considerable heat, which must be dissipated as fast as it is produced. Failure to do so leads to heat stroke (possible even on a cold day), and can cause coma or even death. The evaporation of sweat from the skin is the body's main mechanism for dissipating heat.

The amount of water needed to cool the body through sweat depends on the air temperature and humidity and on the vigour of the exercise, and also varies considerably from one individual to another. Obviously, the higher the air temperature, the more sweat it will take to keep the body temperature down. Higher humidity reduces the effectiveness of the sweating mechanism, so more sweat is needed to produce the same degree of cooling as under lower humidity. Human's vary both in how much heat they produce at a given level of activity, and in their body's tendency to produce sweat under given conditions.

An "average" runner can lose as much as 1.6 litres of water per hour on a hot day, and some much more. Taking in water by normal drinking during a race is not a complete solution, because before the water can be effective it has to pass from the stomach to the small intestine and then through the intestine wall to the blood stream. The normal emptying rate of water from the stomach to the small intestine is only about 0.6 litres per hour, leaving a deficit of about 1 litre per hour in a typical case in hot weather. This is enough to cause an average runner to slow by 3% after one hour and 6% after two hours.

The most important part of the solution to this dilemma is to fill the stomach with water immediately before (i.e. well under 20 minutes before) starting the race, because reliable research has shown that having a stomach full of water can drastically increase the rate at which water is passed to the small intestine. At least 400ml is recommended, followed by a further 100ml every 10 minutes during the race to keep the stomach topped up. This is a lot of water, and it takes some getting used to, so it is important to do it during training runs as well as during a race. I know from experience that you can get used to it surprisingly quickly.

The advantages and disadvantages of using something other than plain water will be discussed later under the headings "Salt" and "Maltodextrin and isotonics". This can affect the rate of transfer through the intestine wall to the blood stream.

Fat
Fat is an essential element in fuelling the body during a long run such as a marathon. If you start the run at just under lactate/ventilatory threshold pace, the fuel consumption will be about 25% fat to 75% carbohydrates. As the available carbohydrate is used up this ratio will change to about 50:50. Unfortunately, fat molecules contain a lower proportion of oxygen than carbohydrate molecules, so more oxygen (about 8% more) must be provided from the lungs via the bloodstream to produce the same energy output. This change over to increased fat utilisation is the phenomenon known as "hitting the wall" in marathon running.

It follows that the more carbohydrate available the better, particularly since the amount of oxygen available is likely to be reduced as a result of dehydration (see the section on water above) just when more is needed. Methods of boosting the amount of carbohydrate available will be discussed under the headings "Carbohydrate" and Maltodextrins and isotonics".

Fat is nevertheless essential, but you can be quite sure that you have more than adequate fat stores in your body without the need of any supplementation, unless you are suffering from severe malnutrition (e.g. anorexia), in which case you should not be considering running anyway.

Sugar
What we commonly call sugar (i.e. the stuff we put in tea or coffee) is more properly called sucrose. There are several other sugars, chemically similar but varying in their degree of sweetness, the best known being dextrose, fructose (found in fruit) and glucose. Glucose is the form actually used by the body to produce energy, and is the form in which the blood carries sugar and converted carbohydrates to the muscles.

However, there is a very strict limit on how much glucose the blood can hold, with any excess normally being stored in the body after conversion to something else. The "something else" is usually fat, but in certain circumstances it can be converted instead to a substance called glycogen (which can be regarded as a storable form of glucose). Other sugars have to be converted to glucose before they can be used to produce energy, or are converted to fat if not required immediately.

Sugar has had a considerable amount of bad publicity, on the grounds that it is accused of causing tooth decay, obesity, diabetes and heart disease. Research has indicated that its effect on diabetes and heart disease is an indirect result of causing obesity, leaving tooth decay and obesity as the two possible causes of concern.

I will not discuss the tooth decay problem other than to say that what matters is how long you have sugar solution in contact with your teeth. If you are going to consume sugary food or drink, swallow it as fast as possible and use a non-sugary drink to clear it from your mouth.

The problem with normal sugar (and that includes honey and brown sugar, which do not contain significant quantities of nutrients) is that it gives the body calories but nothing else. To be healthy we must eat adequate quantities of proteins, vitamins, minerals and fibre, but sugar contains none of these. For the average sedentary individual in a modern industrial society this means sugar should largely be avoided to ensure adequate nutrition without consuming an excess of calories.

An endurance athlete is in a different position. He/she needs to consume far more calories than average to provide the energy burnt up by running, but little more than average of the other nutrients. Sugar and sugary foods are therefore a very useful source of calories, provided they do not replace any of the normal intake of other foods (other than fat).


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