Skip to main content

The Globe and Mail

Too much fuel, or not enough: Both can be a problem for runners

Reid Coolsaet is practising drinking. For weeks if not months leading up to the Scotiabank Toronto Waterfront Marathon, the elite runner will keep detailed information on how much he weighs before and after a workout and how much fluids he takes in during training in order to fine-tune his hydration and fuelling needs come race day. It's an issue even rookie marathon runners need to pay attention to, Mr. Coolsaet says.

"If you can practise [hydrating]before the marathon, it can save you a lot of pain and agony," says Mr. Coolsaet, who lives in Hamilton and trains in Guelph, Ont.

Proper hydration and fuelling is not as simple a matter as drinking when you are thirsty or downing a PowerBar when hunger pangs strike mid-race. Instead, experts say runners need to practice hydrating and fuelling well before an event. Otherwise, they may suffer muscle cramps or worse ailments that can hurt performance or even see them unable to reach the finish line.

Story continues below advertisement

"It's really important that part of the process of training is understanding what works for you and what doesn't," says Samuel Gutman, medical director of the BMO Vancouver Marathon and president of RockDoc Consulting, a Vancouver-based medical-consulting company.

For instance, some runners may find that gels, typically eaten to restore glycogen levels, upset their stomach, Dr. Gutman says. Runners who have never consumed them during training but take a gel midway through a race only to find they get cramps or diarrhea only have themselves to blame since it could have easily been discovered while preparing for the race.

Knowing whether it is best for a particular runner to have gel at the ready or an energy bar can make all the difference when it comes to reaching a goal time.

"In order to finish, even if you're well trained, most people need some kind of nutrition on the course," Dr. Gutman says.

Knowing when you will need nutrition on the course is also essential, says Dan Ouimet, chair of the Calgary Marathon Society.

Get training schedules, watch videos and learn from the pros

"Be sure that you figure out when it is that your energy stores will be depleted," he says. "If you think at mile 15, for example, you will need a reload of energy, you want to start consuming that reload at mile 13 because it's going to take a mile or two for the calories to get in your system and kick into gear."

Story continues below advertisement

Knowing how much fluid to consume during a race is also essential, Mr. Ouimet says. Dehydration can result in cramping, vomiting and fatigue. Taking in too much fluids, a condition known as hyponatremia, can also pose significant problems.

Mr. Ouimet suffered a case of hyponatremia early in his endurance running career. "I started throwing up and I had no clue why," he says of his third marathon. "It turned out I had just drank too much water and not enough electrolytes."

In the worst cases, hyponatremia can result in seizures as the body's stores of sodium are depleted. The condition can even be fatal, says Bruce Minnes, medical director of the Scotiabank Toronto Waterfront Marathon.

The average runner can lose up to two pounds in body fluids during a marathon, depending on the conditions, Dr. Minnes says. And while those fluids can easily be replaced by drinking water or a sports drink such as Gatorade, if a runner continues to feel ill it is best to err on the side of caution.

"It's better to slow down, take in some fluid and something containing carbohydrates," Dr. Minnes says. "If the symptoms are easing up, then get back to it and slowly pick up your pace. If they're not, then you may need to consider drastically reducing your pace, walking or pulling out of the race altogether."

While everyone's hydration needs will differ, the typical marathon runner should consume between half a litre to a litre of fluid per hour, says Andrea Holwegner, a Calgary-based registered dietician. "Most runners actually don't get enough [fluid]"

Story continues below advertisement

Dehydration can even cause a runner's heart rate to spike, Ms. Holwegner says. Anyone who is doing 90 minutes or more of endurance exercise, such as a marathon, should skip water and instead opt for a sports drink in order to replenish their electrolytes, she adds.

And while runners should use their training to develop a strong sense of how much fluid they will need during a race, it is also a good idea to practice running with a water bottle. If you are simply looking to finish, it may not be much of an issue. But if you are going for a personal best, becoming comfortable with running with a bottle or some other container in hand can help you reach your goal time.

"When you're running at a quicker pace, to drink and run and not slow down becomes a challenge in itself," Mr. Coolsaet says.

As well as the physical effects that dehydration and hunger can have on a runner, they can also take a significant psychological toll, Ms. Holwegner says. Feeling hunger pangs or dry mouth can be unnecessary distractions that hurt race performance, she says.

"If you lose the mental game, it can be a very difficult race," she says.

Report an error Licensing Options
About the Author

Dave McGinn writes about fitness trends for the Life section and also reports for Globe Arts. Prior to joining the Globe, he was a freelance journalist, covering topics from trying to eat Michael Phelps' diet to why the Joker is the best villain in comics history. He's working on improving his 10k time. More

Comments are closed

We have closed comments on this story for legal reasons. For more information on our commenting policies and how our community-based moderation works, please read our Community Guidelines and our Terms and Conditions.