Thirst is a natural response to the need for fluid replacement and it must focus on maintaining plasma volume so circulation and sweating progress at optimal levels. Adequate hydration provides the most effective defense against heat stress. A well-hydrated athlete always functions at a higher level than one who is dehydrated.
Hyperhydration or “water parade” can improve temperature regulation in hot weather and this protects against heat stroke. An effective water parade includes:
1. 500 ml of water before sleep
2. 500 ml of water on awakening
3. 500 ml of water 20 mins before exercise
While water parade is effective, it should be noted that when working out in hot weather, the body can lose 2,000 ml of fluid per hour while the stomach only empties about 1,000 ml of water per hour. What about the loss of electrolytes?
I found the following misleading recommendation posted at a public forum.
“Do you exercise or jog? Then make sure you have fluid replacement by drinking not pure water but “isotonic” drink. You can save your money by making your own. Here is the composition for my sports (isotonic) drink-:
200ml ordinary fruit squash
A pinch of salt
Mix them all together in a jug and cool down in fridge.”
I find advice like that rather alarming and I certainly hope nobody would take it seriously. During strenuous exercise, the kidneys have a mechanism that conserves sodium. Sodium loss from sweating is over-estimated because sweat is always hypotonic. It should be noted that electrolyte replacement is not necessary for light exercise like jogging in the evening for 30 minutes. Plain water rehydration will do. Even if electrolyte replacement is required as in endurance training, sodium is something easily obtained from most diets and many of us eating out are already getting more than enough sodium. Too much sodium can raise blood pressure and result in swelling of the extremities. Face and hand swelling are quite common in women who have consumed too much salt before exercising.
Nevertheless, different individuals sweat differently and prolonged exercise in the heat can deplete the body of sodium. The element we should be more concerned about is potassium, so common salt alone won’t do for electrolyte replacement. A good, natural source of potassium would be bananas. Another way to get potassium is from low sodium salts. They are sold at many supermarkets nowadays.
Isotonic drinks are not just bottles of salt water. They not only contain potassium but also citrate which buffers blood pH and reduce the
effects of lactic acid accumulation. Personally, I find bicarbonate to be a more effective buffer against acidosis (symptoms: headache and
nausea). Too much bicarbonate, however, can cause bloating and stomach upset.
You can make your own isotonic drink with oral rehydration tablets or mixtures with pure citrus juices or banana shakes, but I’m not sure if it’s worth the trouble when isotonic drinks are so cheap and readily available. Unless there is excessive sweating or the exercise very intense, just drink plain water. I do consume Gatorade and 100Plus, but I always dilute with water 1:1. Some isotonic drinks in full strength, are known to cause tooth decay.