Drink up and enjoy your summer sport
Waterloo: tennis player John Hui collapses from
dehydration during the Davis Cup. While he was fortunate to return to the
court well enough to win the match, many recreational athletes are poorly
educated in the dangers of not drinking before, during and after exercise.
MARGARET CHENG
Wherever you go in Hong Kong you see plastic waterbottles - in hikers' hands, on taxi drivers' seats, dumped on the streets, floating in the harbour. So news that Hong Kong people are not drinking enough during the hot humid months comes as a surprise. But according to Dr Stephen Wong Heung-sang,assistant professor in the Department of Sports Science and Physical Education at the Chinese University of Hong Kong, most people do not drink enough of the right fluids to replace not just water but also the vital salts and energy lost during hot weather.
And even though sportsmen and women should know better, they, too, allow
themselves to get seriously dehydrated during exercise.
Last year Dr Wong studied female distance runners to see whether changing
the kind of fluids they drank could change their performance. His results
showed that putting carbohydrate (usually sugar or glucose) and salts into
the drink, instead of just taking plain water, significantly improved the
athletes' performances. "We found it would help the runner to run longer,
compared with a placebo [a dummy drink which tasted the same but had no
sugar or salts in it]." Just as importantly, Dr Wong found a significant
number more than 40 per cent) of the athletes did not like to drink at
all while exercising because they feared it would interfere with their
performance. "Subjects reported that usually they didn't drink during training
because they found it disturbing to their pace," he said. "That is one
of the major observations. Many people, especially female runners, have
this misconception that drinking during training or competing is not necessary.
If they changed this practice it would enhance their performance."
One of the runners drank so little her blood tests revealed she was
chronically dehydrated. "Her blood is really sticky . . . but she complained
all the time about our brutality - forcing her to drink." Dr Wong said
while elite athletes were well aware of the need to stay well hydrated,
recreational sportsmen and women (his study was of a group of club runners)
were
still poorly educated about fluid replacement. They still do not know
how much fluid to drink, what they should drink and when they should drink
it.
"What worries me is the recreational sports people. For this group of people the summer weather in Hong Kong could cause serious problems." Could they even collapse and die? "That's right," he said.
Hong Kong is far behind this trend [good fluid replacement] in sports science. Friends working in Prince of Wales Hospital during summer always see Patients suffering heat stroke." Even though many people carry water, few drink enough during the summer months, Dr Wong says. "The reason is they rely on their thirst. But this is not a good indication of their needs. By the time you feel thirsty you are already dehydrated. Your blood osmolality [concentration or "stickiness"] has gone up."
Horse still, many people in Hong Kong have trained themselves to ignore their thirst and drink very little during work hours because they fear having to find and use filthy public toilets.
Dr Wong found this attitude extraordinary among Hong Kong's beauty-conscious women. "Many women spend a lot of money on cosmetics but neglect the fact that drinking plenty of fluids will give them smoother skin and a better appearance!"
While women avoid drinking because Hong Kong's toilets are so unpleasant, for truck and taxi drivers it is an economic choice. "Professional drivers fear getting a ticket if they park the car somewhere for a few minutes while going to the toilet. So they don't drink," Dr Wong said.
So many people are reminded to carry a water bottle - and they do carry it - but they don't drink."
The problems do not stop there. Water is not the ideal form of fluid replacement, especially if exercising during hot weather.
This is because water has no taste," he said. "Palatability is important."
Along with lack of taste, water does not replace lost energy or salts.
Dr Wong's study, the first to look at Asian women, confirmed overseas research
showing You need to take in some form of carbohydrate and salt, as well
as water, to keep the body cells functioning well.
For athletes trying to squeeze high levels of performance out of their muscles, brain and heart, all body cells need to be functioning optimally, not just normally.
To achieve this, the cells need a constant supply of energy, salt, water and oxygen. The oxygen comes from a faster rate of breathing, but the rest comes from either what is stored in the body, or the fluids we drink.
Many sports coaches and commercial companies have come up with different formulae they claim will meet those needs, but Dr Wong says there are only three sports drinks" on the Hong Kong market which truly supply the right levels of fluid, carbohydrate and salts.
The best way to work out whether a "sports drink" will help stave off dehydration is to look at the levels of carbohydrate and sodium in the ingredients list marked on the can or bottle.
The ideal carbohydrate level is six to seven per cent or six to seven grams per 100 millilitres. Sodium should be between 120 and 140 millimoles per litre while potassium levels need to be between four and five millimoles per litre.
Along with the right salt and carbohydrate levels, the drink should not be carbonated. The gas bubbles in carbonated drinks collect in the stomach and intestines and cause the pains known as "stitches" when people run.
Knowing how much to drink is as important as knowing what to drink. It is now recommended that before exercising adults should drink at least 120ml to 240ml of fluid. During exercise, the same amount - 120ml to 240ml - should be drunk every 15 to 20 minutes.
And after exercise, it is crucial that 150 per cent of fluid lost is replaced. If not, the body is left weakened and will not recover in time for the next competition or training session.
This 150 per cent figure can be calculated by weighing yourself before and after exercise. For every kilogram of weight lost during exercise, you need to drink 1.5 litres of fluid. Dr Wong recommends that scales be put in every changing room and that all athletes - from primary school upwards - learn to weigh themselves and replace lost fluids.
On top of that, coaches, teachers and parents need to explain to children the signs of dehydration. The easiest way is to look at the colour of the urine they pass. If the urine is a dark yellow or even brown, this indicates the body is so dehydrated the kidneys are trying to compensate by making the urine more concentrated.
Normal urine is a pale yellow.
While many top athletes are getting excellent dietary and fluid advice
at the Hong Kong Sports Institute, Dr Wong says in some sports the need
for good fluid replacement after competition is virtually ignored. People
head off for a beer or two, making their dehydration much worse.
Soccer players are the worst when it comes to most-match recovery because
there is a tradition of bringing winning teams to seafood banquets after
a
match. "This is not a good practice. They should be given noodles and
soup after the match. But they would complain and ask their manager: 'Why
are you so stingy?' "
