Never Mind the Bullocks, Here's the Science by Karl Kruszelnicki Page B
Authors: Karl Kruszelnicki
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The study was carried out by Dr E.S. Chambers and colleagues from the School of Exercise and Sports Science at the University of Birmingham in the UK. They worked with eight trained cyclists, who had fasted for six hours. The cyclists had to perform at 75% of their maximum workload for about one hour. They swished their mouths with a liquid eight times during that hour and, on each occasion, spat it all out into a bowl after ten seconds. The liquid either contained sugars or, if it had no sugar, it tasted sweet thanks to the addition of saccharin and aspartame (artificial non-calorie sweeteners).
The results were amazing. When the exercising cyclists swished their mouths with saccharin/ aspartame water, they performed at a certain level. But when they swished 6.4% carbohydrate (sugar) solution in their mouths, their performance improved by an astonishing 2-3%.
Why? We don’t really know. We do know that individual muscle fibres will fatigue after lots of work. And we also know that there is some poorly understood central brain control of ‘fatigue’. Another part of this study looked at brain activity. It found that a part of the brain involved in ‘reward’ became active when the mouth experienced a swish with the sugar solution.
Drink Too Much…
Sports physiologists also agree that it is possible to drink too much.
A tragic example of this occurred in the 2002 Boston Marathon. (Coincidentally, sports scientists wrote a paper in The New England Journal of Medicine on that very marathon.)
A few months before the marathon, newspaper advertisements for a major sports drink encouraged marathon runners who might enter to drink at least 1,200 ml/hr, or else ‘…your performance could suffer…’. A marathon is the classic case where a sports drink can help. Two-thirds of the 766 runners provided a blood sample at the end of the marathon. Of those, about 13% had drunk so much liquid—more than they had lost in sweating, breathing, etc—that they had actually gained weight and had diluted their blood sodium to somewhat worryingly low levels. Low sodium levels cause symptoms that include: ‘headache, vomiting, swollen hands and feet, restlessness, undue fatigue, confusion and disorientation (due to progressive encephalopathy), and wheezy breathing (due to pulmonary oedema). When plasma sodium falls…(further)…the chances increase for severe cerebral oedema with seizure, coma, brainstem herniation, respiratory arrest, and death.’ One competitor, 28-year-old Dr Cynthia Lucero, actually died because her sodium levels were too low, from drinking too much. The autopsy report stated that her death was due to ‘ingesting too much Gatorade’.
Mind you, death can also happen by drinking too much fluid of any type, and in situations unrelated to sport. Fatalities have occurred in workplace drug testing (where people have tried to ‘flush’ drug residues out of their bodies to avoid detection in their urine samples) or drinking contests (such as a radio station-sponsored competition in which the last person ‘standing’ before having to urinate wins a prize). And it’s alwaysmore of a risk with those who have a smaller body mass (e.g. women).
Indeed, some people wrongly think that it is impossible to drink too much, and that drinking too much cannot harm you.
It is important to understand your body, and how it behaves in any sport you do, and to drink the correct amount (not too much, not too little). You can use your change in body weight as a guide, and assume that a loss of 1 kg means that you have lost 1 litre of sweat. It’s a rough approximation, but it’s close enough.
You Might Need It…
Yes, sports drinks have their advantages—especially if you work out for an hour or more. And, of course, they can help if you sweat profusely.
One study looked at voluntary drinking in boys who were exercising hard for a few hours in the heat. If the water had some added flavouring, it tasted nicer so they
The study was carried out by Dr E.S. Chambers and colleagues from the School of Exercise and Sports Science at the University of Birmingham in the UK. They worked with eight trained cyclists, who had fasted for six hours. The cyclists had to perform at 75% of their maximum workload for about one hour. They swished their mouths with a liquid eight times during that hour and, on each occasion, spat it all out into a bowl after ten seconds. The liquid either contained sugars or, if it had no sugar, it tasted sweet thanks to the addition of saccharin and aspartame (artificial non-calorie sweeteners).
The results were amazing. When the exercising cyclists swished their mouths with saccharin/ aspartame water, they performed at a certain level. But when they swished 6.4% carbohydrate (sugar) solution in their mouths, their performance improved by an astonishing 2-3%.
Why? We don’t really know. We do know that individual muscle fibres will fatigue after lots of work. And we also know that there is some poorly understood central brain control of ‘fatigue’. Another part of this study looked at brain activity. It found that a part of the brain involved in ‘reward’ became active when the mouth experienced a swish with the sugar solution.
Drink Too Much…
Sports physiologists also agree that it is possible to drink too much.
A tragic example of this occurred in the 2002 Boston Marathon. (Coincidentally, sports scientists wrote a paper in The New England Journal of Medicine on that very marathon.)
A few months before the marathon, newspaper advertisements for a major sports drink encouraged marathon runners who might enter to drink at least 1,200 ml/hr, or else ‘…your performance could suffer…’. A marathon is the classic case where a sports drink can help. Two-thirds of the 766 runners provided a blood sample at the end of the marathon. Of those, about 13% had drunk so much liquid—more than they had lost in sweating, breathing, etc—that they had actually gained weight and had diluted their blood sodium to somewhat worryingly low levels. Low sodium levels cause symptoms that include: ‘headache, vomiting, swollen hands and feet, restlessness, undue fatigue, confusion and disorientation (due to progressive encephalopathy), and wheezy breathing (due to pulmonary oedema). When plasma sodium falls…(further)…the chances increase for severe cerebral oedema with seizure, coma, brainstem herniation, respiratory arrest, and death.’ One competitor, 28-year-old Dr Cynthia Lucero, actually died because her sodium levels were too low, from drinking too much. The autopsy report stated that her death was due to ‘ingesting too much Gatorade’.
Mind you, death can also happen by drinking too much fluid of any type, and in situations unrelated to sport. Fatalities have occurred in workplace drug testing (where people have tried to ‘flush’ drug residues out of their bodies to avoid detection in their urine samples) or drinking contests (such as a radio station-sponsored competition in which the last person ‘standing’ before having to urinate wins a prize). And it’s alwaysmore of a risk with those who have a smaller body mass (e.g. women).
Indeed, some people wrongly think that it is impossible to drink too much, and that drinking too much cannot harm you.
It is important to understand your body, and how it behaves in any sport you do, and to drink the correct amount (not too much, not too little). You can use your change in body weight as a guide, and assume that a loss of 1 kg means that you have lost 1 litre of sweat. It’s a rough approximation, but it’s close enough.
You Might Need It…
Yes, sports drinks have their advantages—especially if you work out for an hour or more. And, of course, they can help if you sweat profusely.
One study looked at voluntary drinking in boys who were exercising hard for a few hours in the heat. If the water had some added flavouring, it tasted nicer so they
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