Never Mind the Bullocks, Here's the Science by Karl Kruszelnicki

intestinal fluid absorption). And it had a lower sodium concentration (to make it more palatable).
    It was formulated in 1965 by Dr R. Cade at the University of Florida, to support the Florida Gators Football Team, who, at that time, were on a losing streak. American Football games last for hours, and in the hot and humid climate the players sweated massively and suffered from mild dehydration. The energising and rehydrating effects of the sugars and salts in the Gatorade did help the Florida Gators in the crucial second half of their games. In 1967, for the first time, the Gators won the coveted Orange Bowl.
    The Kansas City Chiefs, from Missouri, also had problems with their players flagging in the second half. They too tried Gatorade, which was credited with helping them achieve impressive victories.
    Use of Sports Drinks
    Some 40 years later, sports drinks are big business. In fact, Gatorade has—after a few legal battles—earned over $80 million for the University of Florida.
    By the way, in the bottled drink trade, the sugars and salts are known as ‘pixie dust’ or ‘fairy dust’.
    Sports scientists all agree that a little pixie dust does help water absorption. It also helps to maintain your ‘Thirst Drive’. The salts make you feel thirsty, and/or the flavouring makes it more delicious—either way, you drink more.
    They also agree that highly trained athletes who sweat a lot each day, thanks to several hours of hard exercise in a hot environment, need sugars to provide fuel for the muscles and brain, and electrolytes and water to replace the losses from heavy sweating. Indeed, many athletes struggle to consume sufficient carbohydrates to meet their daily needs. These athletes would include marathon runners, large football players and tennis players who train for long hours.
    But do the rest of us need sports drinks?
    To answer that question, you need to realise that the goal of drinking during exercise is to replace the water lost from sweating (and other water losses, such as from urination).
    Sweat 101
    When you don’t exercise, your kidneys manufacture urine at 20-1,000 ml/hr. But during exercise, the kidneys decrease their rate of manufacture of urine.
    How much you sweat is very variable. It depends on environmental conditions—wind and sun exposure, temperature, humidity, sky and ground radiation, etc. It also depends on local conditions—your metabolic rate, your metabolic efficiency (how much work you produce for a given effort), your body weight, your clothing, how hard you work, your history of heat acclimatisation, etc.
    Sweating is the major pathway for removing heat during vigorous exercise in warm to hot weather. (Actually, it’s the evaporation that removes the heat, but you have to sweat a liquidonto your skin before you can evaporate it away.) People working hard can generate 1,000 watts. If their metabolic efficiency is 20%, then they have to get rid of 800 watts continuously, which requires the generation of about 1.2 litres of sweat.
    Sweat contains both water and salts. The salts include 5 milliequivalents per litre (mEq/litre) of potassium (range 3-15), 1 mEq/litre of calcium (range 0.3-2), 0.8 mEq/litre of magnesium (range 0.2-1.5) and 30 mEq/litre of chloride (range 5-60).
    The effect of sweating is to remove water from the body, i.e. to reduce your Total Body Water (TBW). Your TBW ranges between 45% and 75% of Total Body Mass, the average being 60%. Your TBW is generally regulated to within +/- 0.2-0.5% of Total Body Mass. However, during the post-ovulation phase of the menstrual cycle, women can increase their Total Body Mass by up to 2 kg (due to increased water retention).
    But with exercise in hot conditions, a sudden drop of 2% in TBW degrades aerobic and mental performance to an easily detectable level. This 2% drop is a strong warning signal that the athlete is entering a potentially dangerous zone.
Warning – Numbers Ahead!
800 watts = 0.8 kW = 0.8 kJ/sec = 48 kJ/min =