How Much Should I Drink?

A refresher course on how much – and what – to drink on hot summer runs

During the blazing days of summer, you need more than sunscreen to protect your body from the sun. “Hydration becomes most important during intense exercise in the heat,” says Douglas Casa, Ph.D., who heads the University of Connecticut’s Korey Stringer Institute, which studies heatstroke and other causes of sudden death in sports. “If you’re not adequately hydrated, your blood volume drops, which means your heart has to work harder to power your muscles and keep you cool. When that happens, your running performance suffers.”

While it’s important to stay relatively hydrated during exercise, it’s impossible to create one-size-fits-all drinking guidelines. Every runner’s needs are different. Your body weight, sweat rate and effort level, along with the temperature, humidity and elevation, affect how much you should drink. That doesn’t mean you should leave your hydration plan up to chance. These strategies can help ensure you drink the right amount before, during, and after every run.

Before Your Run

One of the best ways to limit the effects of dehydration during a run is to start ahead of the game and drink enough before it. “Checking your urine pre-run is an easy way to see if you’re prepared,” says Anthony Meade, Adelaide-based sports dietitian. “If it’s clear and copious, maybe you’re drinking too much. If it’s the colour of iced tea, you need to drink more. If it’s a pale lemonade or straw colour, you’re probably adequately hydrated.”

How much you should drink depends on how soon you’ll be running, what your stomach can tolerate, and how hydrated you are. “Typically, most people can handle 180-240mL right before a run,” says Meade. With the exception of alcohol, which has a diuretic effect, all beverages, including water, sports drink, coffee, tea, juice and milk, can help keep you hydrated throughout the day.

If you find you’re often dehydrated before a run, think about consistent fluid intake throughout the day and make sure to have a beverage with all your meals. Have a water bottle handy and visible so it reminds you to drink.

During Your Run

If you’re heading out for a 30K, drinking mid-run is a no-brainer. But what if you’re going for an hour? Or doing 45 minutes of intervals? “There have been a range of recommendations during the past two decades,” says Meade. “One of the alternatives brings us back to basics: drink to your thirst.” It’s advice backed up by the International Marathon Medical Directors Association and Tim Noakes, M.D., author of Waterlogged: The Serious Problem of Overhydration in Endurance Sports. “Your thirst mechanism is exquisitely tuned to your body,” says Dr. Noakes. “Some runners get thirsty quickly; others can go hours without feeling the need to drink much. If you drink when you’re thirsty, you’ll stay adequately hydrated.” That said, Casa and Meade suggest always drinking on runs 90 minutes or longer.

The American College of Sports Medicine offers another approach; it recommends drinking enough so you don’t lose more than three per cent of your weight through sweat. “Lose more than that and your performance starts to falter,” says Casa. One way to figure out how much you lose during an hour of running is to weigh yourself naked pre- and post-run (don’t forget to account for any fluid you take in during that time). Losing 450 grams means you sweated 450mL in one hour. “The goal isn’t to match that loss during a run, but to come within a reasonable amount,” says Meade.

Should you choose sports drinks or water? On runs longer than 60 minutes, sports drinks are a good idea. They have valuable carbs that your muscles need for energy. Meade notes they also contain electrolytes like sodium and potassium, which are lost through sweat but are integral to the absorption and retention of fluids, and contribute to your body’s water balance.

After Your Run

When you come in from a run, drink until you’re satisfied, but don’t rest on your laurels. “Using thirst as your guide and consuming liquids with your meals is adequate after shorter runs,” says Meade. If your face has white salt streaks on it post-run, it means you’ve lost quite a bit of sodium, so it’s best to have a sports drink, or water along with food that contains sodium, says Meade.

After especially long or hard runs, you also need protein to help your muscles recover. That’s why recovery drinks are ideal – they provide protein and fluid to help you rehydrate. “Chocolate milk is a proven choice,” says Meade. “The carbs-to-protein ratio is perfect for recovery.”

If you’re working out again within 12 hours – say you ran at night and you’re planning to run again in the morning – try to be more diligent about rehydrating. Sip liquids regularly until your urine is back to pale or straw yellow and your weight returns to normal.

To help reduce the chance of an upset stomach during a race, practice your hydration plan on training runs that mimic your race-day pace.

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