Don't wait to be thirsty to have a glass of water. Have enough fluids to improve your performance and concentration.

With every drop of sweat that trickles down one loses nutrients, salt and most importantly water that can cause dehydration if not enough fluid is provided, according to a dietician here that was quoted by 'Herald Sun' report.

Dehydration can cause headaches, poor concentration, and cramp. It can be caused by not drinking enough during exercise, or by a lack of fluid intake while sitting at your desk.

"Under normal conditions we need between two and three litres of fluid per day," dietician Lisa Sutherland said adding "You reach this amount by the total amount of fluids you drink, plus the foods you eat. Water should make up a large proportion of total daily fluid intake as a low-calorie, low-sugar beverage.

"For most people eight 250 ml glasses (1 cup) will be sufficient. “But if its hot or you’re exercising, you will need more," she said. People often wait until they feel thirsty to act, but this is way too late, she added.

"Substantial amounts of water are lost through sweating when exercising vigorously. Exercise in hot or humid weather will result in additional fluid loss and increase the risk of dehydration," Sutherland said.

"Even small degrees of dehydration will cause a decrease in exercise performance and your ability to concentrate", she added.