Madhu Gopal, of Ilam Primary School, asks :-

Why do we sweat?

Martin Toomey, a physical education specialist at Otago University's School of Physical Education and who assists the preparation of top sports people, responded.

There are four ways in which the body can maintain a constant or comfortable temperature; conduction, convection, radiation or evaporation. In evaporation heat energy is used to turn a liquid (eg sweat) into a gas (eg water vapour).

When the air temperature approaches the temperature of the body, conduction and convection become ineffective as there is not sufficient temperature difference to promote heat loss. As air temperatures equal or rise above body temperature sweating is the only effective way of cooling the body.

In the absence of sweating the body can become too hot (hyperthermic) which not only influences sports performance but can also place severe stress on the internal organs of the body. It is important that fluid levels are high so that the body can afford to lose water and ions through sweat without having detrimental effects on blood volume and blood pressure. In some environments it is possible for athletes to lose up to two litres of sweat per hour.

Hence it is important that athletes consume large quantities of water or fluid replacement (drinks containing ions such as potassium and sodium that are lost in the sweat) during competition in hot environments. You can also see why marathons are run during the coolest part of the day wherever possible.