Absolute deficiencies are rare and relative deficiencies a little more common.
1. Sodium and chlorine fall markedly after copious perspiration, protracted physical effort and in hot weather, thus causing fatigue, cramps, and insomnia. Under these circumstances previous taking of salt increases endurance. sLosses of potassium must also be compensated by administration of that element, which is also indicated in hypoglycaemic conditions following intense muscular fatigue.
2. Magnesium, phosphorus, sulphur, and iodine are found in normal quantities in a balanced diet.
3. The trace elements
Fluorine, zinc, cobalt and other substances, including copper and manganese, are also found in normal quantities in a balanced diet.
Young persons whose calcium requirements are large may find a deficiency if their intake of dairy products is inadequate.
This is indicated in cases of inapparent anaemia, which are more common than is generally believed, and also when sport is practised at high altitudes, and sometimes in women during their menstrual periods.
Medicaments affecting the cardiovascular and respiratory systems
1. Respiratory tonics such as camphor and its substitutes, lobeline, Micorene, etc. are used with a view to stimulating the respiratory centre. It is extremely doubtful whether they are of any value.
2. The bronchodilators, such as adrenalin and isoprenaline, often produce untoward reactions such as palpitations, arterial hypertension and hypotension, etc.
3. Cardiotonics, particulary the digitalis heterosides, only have an effect in incipient heart failure.
4. The cardiac stimulants (camphor, nikethamide) have a stimulating effect on the heart through the bulbar centres. They are of no value for athletes.
5. Vasoconstrictors, such as adrenalin and its derivatives, are primarily used in cases of general hypotension and collapse. Their hypertensive effect will hardly be of any value during or after physical exhaustion in an athlete. In normal individuals they are altogether inadvisable.
6. The vasodilators (nitrites and derivatives of nicotinic acid) are inadvisable because of their hypotensive effect, and their untoward indirect effects on the heart may bring about circulatory collapse.
7. Beta-adrenergic blocking agents reduce exercise tachycardia and stress in ski jumpers.