Physiological Principles of Exercises & Sports
- A brief discussion -
- Part 4 -

By Dr. Hanjabam Cha Barun *

Physiology of Body fluids & salts in exercise

Normally the daily output of water is about 2.3 liters & we should ingest fluid more than 2.1 liters per day (700ml, approx. 2.8glasses of water, as water in cooking; & more than 1.4 liters as the fluid by mouth as water & beverages, approx.> 5.6glasses of water). In prolonged & heavy exercise, the daily output of water increases more than 2.87 times, & therefore the fluid ingested should be more than 3.05 times the normal value (more than 5.7 liters of fluid by mouth as water & beverages, approx. > 22.8glasses of water).

During heavy exercise or in very hot weather, water loss in sweat may increase to 1-2 liters per hour or almost 50 times normal value per day. Similarly, in prolonged & heavy exercise, insensible water lost through lungs increases almost 2 times that of the normal value per day. All of this will rapidly deplete the body fluids unless adequately taken.

More than 70% of body weight (some say-60% of body weight is total body water) is because of the water it has. Loss of water upto 10% of the total body water, makes a person feel extremely tired & fatigued. A more than 20% loss may result in death. As much as 2.268 to 4.538kg weight loss has been recorded in athletes in a period of one hour during endurance athletic events under hot & humid conditions.

This mainly results from loss of sweat. Loss of enough sweat to decrease body weight only 3% can significantly diminish a person's performance, & a 5 to 10% rapid decrease in weight can often lead to serious muscle cramps, nausea etc. Hence it is essential to replace fluids as it is lost.

Sweat contains large amount of sodium chloride, some urea & lactic acid. So, considerable amount of salt is lost through sweating. The sweat glands, however, become acclimatized when an athlete becomes acclimatized to the heat by progressive increase in athletic exposure over a period of 1 to 2 weeks rather than performing maximal athletic feats on the first day (acclimatization to heat: the various physiological readjustments & compensatory mechanisms in the body that reduces the bad effects of prolonged heat exposure).

This acclimatization of sweat glands results mainly due to increase secretion of aldosterone by the adrenal cortex. The aldosterone increases the reabsorption of sodium chloride from the sweat & urine, & loss of potassium through sweat & urine.

This leads to an important conclusion-(a) Salt supplementation should be there for all athletes performing exercise on hot & humid days, but once the athletes are acclimatized, only rarely do the salt supplementation need to be considered during the sporting events. Hence there may at many a times be over dose of this salt supplementation which is equally harmful. (b) Some of the supplemental fluids of athletics should also contain proportioned amounts of potassium along with sodium, usually in the form of fruits juices & coconut water etc.

Basic Sport Pharmacology

(a)Caffeine (found in coffee) is said to increase athletic performance, but reliable data are lacking.

(b)Androgens/male sex hormones or any other anabolic steroids. They can increase muscle strength & increase athletic performance. These are banned drugs in sports. They causes hypertension, promote heart attacks & strokes. External male sex hormone preparation decreases testicular function, may lead to infertility & decreases the secretion of the person own hormone. In females, musculinization can take place-hirsutism, bass voice, ruddy skin, cessation of menses, infertility etc.

(c)Others drugs such as amphetamines, cocaine (a narcotic drug) etc have been said to increase one's athletic performance, mainly due to psychic stimulant. The overuse can lead to deterioration of performance. Such drugs may interact with the epinephrine & norepinephrine (catecholamines) released during exercise, & may cause over excitability of the heart, leading to ventricular fibrillation which may lead to the death of athletes within seconds.

(d)Nicotine, present in tobacco smoking, is widely regarded as one of the biggest enemy of an athlete. It causes constriction of the terminals bronchioles of the lungs, increasing the airflow into & out of them. Nicotine paralyzes the cilia on the surfaces of the respiratory epithelial cells that normally beat continuously to remove excess fluids & foreign particles from the respiratory passageways, resulting in much accumulation of debris in the air-passages adding further difficulty of breathing. The irritating effects of the smoke itself cause increase fluid secretion into the bronchial tree, as well as swelling of the epithelial linings. All of these mean that mean that even a light smoker will feel respiratory strain during maximal exercise, reducing his/her performance significantly.

(e)Alcohol is a neuronal depressant. Any measurable concentration of alcohol produces a measurable slowing of reflexes- performance is impaired, fine discrimination & precise movements are obliterated & errors increases. Chronic alcoholism damages brain neurons. In small doses, BP is not affected much, but moderate doses may cause mild rise in BP due to increase muscular activity & sympathetic stimulation & also causing tachycardia. This may interact with the exercise induced rise in catecholamines & may produce dangerous results.

In large doses, alcohol causes direct myocardial & vasomotor center depressant with fall in BP. Chronic alcoholism causes hypertension, cardiomyopathy & cardiac arrhythmias, & megaloblastic anaemia etc. Alcohol is a depressant on respiratory centre, but may transiently stimulate respiration reflexly due to its mucosal irritating nature. Chronic alcoholism also causes muscles weakness & myopathy, & its high doses depress temperature regulating center & deplete hepatic glycogen causing hypoglyceamia. All these mean alcohol should be avoided, specially by competiting athletes & sport persons.

Prolongation of life is possible through sport & fitness
Mortality is shown to be 3 times less among people who maintain appropriate body fitness, using judicious regimes of exercise & weight control, specially between the ages of 50 & 70. These may be due to the cardiovascular protective effect of body fitness: maintenance of moderately lowered blood pressure, & reduced blood cholesterol & decrease ratio of LDL (enemy lipoprotein) to HDL (protective or friendly lipoprotein).

Another important point is that athletically fit person has more bodily reserves to call on when he or she does become sick. For example an athletically fit old man has twice as much as respiratory reserve (ability to increase oxygen delivery to the tissues in times of need)as a non fit old man, & 50% greater cardiac reserve (ability to increase cardiac output in times of need) than in a non fit old man.

Hence, understanding exercise physiology & the scientific data thus collected has been used to improve the performance of athletes, sportsmen & military personnel.

The knowledge of this field also helps a physician in many ways- aiding the diagnosis of heart & lung diseases; pre- & post-operated assessment of cardio-thoracic surgical patients; rehabilitation of cardiac invalids; & screening workers for disability compensation etc.

For players & coaches also, the basic understanding of sport & exercise physiology will definitely help increase their efficiency & performance.

Concluded...