Stay Hydrated in the Heat when Exercising Outdoors

Working out in the heat can be dangerous unless you're smart about hydrating appropriately

Credit: Flickr/Mike L Baird

Drinking the right amount of fluids is crucial when exercising outdoors in hot weather

Performing outdoor exercise in the heat requires you to pay attention to what you’re drinking and stay well hydrated.

It may have taken awhile to get here but summer is now in full force and I love working out in the hot weather. Yesterday morning I had a couple of free hours between training clients so I went paddleboarding and trail running in Deep Cove.

A lot of people may tell you not to exercise outdoors in the heat, but I don’t believe in such a blanket warning. You can safely exercise in hot weather, you just have to be smart about it.

As an example, look at the annual Knee Knackering North Shore Trail Run. This is a race I’ve done numerous times and this year 206 runners competed during a heatwave. Even though temperatures reached over 26 degrees, 93% of the runners safely finished the ultramarathon, which winds 30 miles along the Baden Powell trail from West Vancouver to Deep Cove.

By staying adequately hydrated, the finishers were able to push themselves at a high intensity for five to 10 hours. You may not be exercising to such extremes, but if you follow my guidelines, you too will able to safely participate in your favourite activities this summer .

Hyponatremia (aka drinking too much water)

You’re probably thinking that if you drink water you’ll be fine. But you can actually drink too much water if you’re exercising intensely for a long period (over two hours).

A condition called hyponatremia, also known as “water intoxification,” can occur in such cases. Marathon runners have even died because of it.

Essentially, the profuse sweating and excess water intake dilute the sodium levels in your blood to extremely low levels. Sodium along with potassium, calcium, magnesium and chloride are also referred to as electrolytes; minerals that perform important physiological functions. Diluting them too much can cause a host of problems including death. This is extremely rare but it can happen.

I’m not saying you shouldn’t drink water, but there are circumstances when plain water isn’t the most appropriate drink.

At the other end of the spectrum, if you aren’t taking in enough fluids during exercise, you’ll get dehydrated which can cause you to perform poorly, feel weak, collapse or in extreme cases, die. So you’re in trouble if you drink too little water as well.

How Much to Drink in Hot Weather

But don’t fret. Like I said, you can safely exercise in the heat if you take some precautions.

First, make sure you’re hydrated before you start out the door. Drink two to three litres (yes, LITRES) of water per day during the summer. Aim for the upper end of the range on your active days.

Take in 500 ml of water one to two hours before your activity to ensure you’re topped up.

Once you’re outdoors, water is fine to consume if your workout lasts an hour or less. Drink anywhere from 500 ml to a litre.

But if you’re going to be exercising for any longer than that, it’s better to drink a fluid that contains electrolytes. Look for products that contain a full spectrum of electrolytes: calcium, magnesium, potassium and sodium chloride (salt). These are a better option than ones that only contain one or two electrolytes.

You can buy pre-mixed drinks or a powder you mix yourself (the more economical option). You can also buy electrolyte capsules that you drink with water. These are handy if you don’t like the taste of the drinks and prefer to drink plain water. Follow the directions on the label as to how many to take.

Drink 500 to 750 ml of your electrolyte drink per hour. If taking the capsules, drink 500 – 750 ml of water per hour. If you’re a bigger person or sweating a lot shoot for the higher number.

You can find electrolyte drinks at most supplement stores as well as running stores. Some of the products I’ve used with success are Eload and Hammer Nutrition. 

So have fun doing the Grouse Grind this summer, just remember to take your fluids with you!