水與運動的關係和重要性 | Gym Blog by Fitness First Hong Kong
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水與運動的關係和重要性

大家不要把大口喝水視為理所當然

18 三月 2019

When to drink water and how much of it? There’s no one-size-fits-all recommendation but you can find out what works best for you.

We take it for granted because it’s on tap, but the origin of our water is from outer space! It’s the most-abundant element in our bodies and is used to regulate temperature, perspiration and urination, and blood pressure, for example. But proper hydration is not simply about the volume of water we drink; the regulation of fluid in our bodies is much more sophisticated. It involves the homeostatic regulation of total body fluid volume, composition and distribution. Homeostasis refers to the body’s different systems being in equilibrium.

So how much should you drink everyday so it stays that way? This generally depends on your:
● individual physiology
● lifestyle
● what activity you’re doing (running a marathon or a round of golf?)
● how vigorously you’re doing it
● whether you’re doing it indoors or outdoors
● the climate where you live, and
● today’s weather

Bear in mind we also ingest water through eating; some 20 percent of daily fluid intake is estimated to be from food. Should you drink eight glasses of water a day? Not necessarily. This advice that has taken over the internet is not backed up by scientific research. It all depends on the factors above.

Drink when you’re thirsty. It’s your body’s signal to you to help it regulate its fluid balance. But don’t drink continuously throughout your workout or your body will be forced to keep readjusting itself to maintain homeostasis. You’ll know this is happening when you feel bloated or uncomfortable.

Working out outdoors under the sun?
That said, it’s important to ensure you’re comfortably hydrated before you start your workout, especially outdoors during a hot day. Be aware that it can be cloudy and still dehydrating out there, but you might not realise this, such as when you’re swimming. In such conditions, make sure to drink after your workout as well, until you begin to feel less thirsty.

Do so calmly. Observe that professional athletes take only occasional breaks for water, and then they do not glug it down. Don’t drink in the middle of active play or workouts. (Marathons are something else; see below.)

Signs of dehydration
The symptoms of mild dehydration are fatigue, dizziness, and mild disorientation. They usually cause a little discomfort, but are resolved by rest and drinking water. Severe dehydration is of course a medical emergency, but is unlikely to happen in an air-conditioned gym under the supervision of qualified trainers. Running outdoors in the midday sun in the city? Don’t do it.

What happens if you drink too much water?
It dilutes electrolytes in your blood, such as sodium which helps balance the amount of fluids inside and outside of cells via osmotic pressure (the exchange of minerals between fluids). If sodium levels drop from excess water intake, your cells will swell from absorbing more water. When this happens to brain cells, pressure can build up inside the skull, leading to headache, nausea, vomiting and cramping, which can be misinterpreted as symptoms of dehydration. Marathon runners have been known to overcompensate for dehydration, especially if they drink a large volume within a short time. Because our kidneys cannot excrete more than a liter per hour, it is thought that we should not drink beyond this amount in this duration.


Takeaway: What’s the ambient temperature like where you’re working out? Be aware of this but otherwise, just drink when thirsty. Don’t overrule your body’s thirst signals with theory and unproven recommendations that lead to neuroses. Enjoy your workout!