Monsoon fitness

Sweating begins within the first few seconds of exercise. By 30 minutes,the rate of sweating reaches a steady level that is determined by exercise intensity and environmental conditions.
Interestingly,in high humidity conditions,evaporation of sweat is significantly reduced. In this situation,sweating is nothing more than a useless loss of water and electrolytes. Rather,formation of copious sweat may lead to dehydration,which may further increase core body temperature.

Strenuous physical effort in hot and/or humid weather may be particularly dangerous in patients with heart disease,kidney disease or those on medication for high blood pressure. During hot and humid climate,an increase in heart rate during exercise results in increased oxygen demand of the heart muscle,which may not be possible to meet in coronary heart disease with narrowing of arteries. Fluid loss equivalent to one per cent of body weight may cause a significant increase in core temperature. This can precipitate angina or arrhythmias (irregular heart beats) during exercise in hot weather.

Taking certain precautions can prevent heat stress injuries. These include:
Acclimatisation: Subsequent to repeated bouts of exercise in a hot environment,there is a marked improvement in the physiologic responses (exercise capacity and heat tolerance). This improved tolerance to exercise in heat is known as heat acclimatisation. In healthy individuals,acclimatisation to heat occurs by the end of first week of exposure.

Place and time: Exercise in hot weather is best undertaken in shade. Exposure to direct sunlight should be avoided. Early morning or late evenings are better than midday. During indoor exercises,good air movement with fan or air-conditioning prevents heat injury and increases exercise capacity.

Clothing: Minimal amounts of porous,light-colored,loose clothing permit free circulation of air between the skin and the environment. Light colors reflect away the heat while dark colours absorb it. Cotton clothing is the best because it absorbs the moisture readily. Ideally,avoid wiping sweat during exercise. Evaporative cooling is thwarted by continually drying the skin before sweat has a chance to evaporate. Sweat per se does not cool the skin. It is evaporation of sweat that cools the skin.

Hydration: Sweat losses during strenuous exercise in the heat may reach as much as 1.5 litres per hour and may be more in humidity. Drink water before,during and after exercise. Thirst is not a reliable indicator of dehydration because a person can lose as much as two per cent of body water before feeling thirsty. Therefore,one should not wait to become thirsty before reaching for water. Water should be taken every 15-20 minutes during exercise.

When a person is prone to sodium loss,about 1/3 of a teaspoon of table salt may be added to a litre of water. Potassium loss in sweat may be replaced by potassium-rich foods citrus fruits and banana.
Pace: Overexertion in hot and humid weather increases the risk of heat injury. Even,acclimatised people are at risk. Exercise intensity should not cross a moderate level in high humidity and temperatures.