Q&A with Dr. Beth Mansfield

This month we received some questions about carbo-loading and race-day fueling. So, we put the question to Beth Mansfield, Ph.D., of Peak Performance: What should we be eating in the days leading up to the race to make sure we’ve got enough energy to make it to the finish?

Beth answers:

Elite marathon runners get most of their energy to run their distance from carbohydrates. Yet they only have enough stored carbohydrate to last about 30-35 km of their race. This means that they need to carbo-load as well as consume carbohydrates during their races.

Recreational runners, however, who take more time to finish their race distance, need to carbo-load AND consume EVEN MORE carbohydrates during their races.

What many runners don’t realize is that simply tapering your training during the week of your race, while maintaining the same carbohydrate intake as if you were doing a full training week of running, should suffice for carb loading.

If you have carb-loaded successfully, you should expect to see your weight go up on the scale by about 2%. This is water weight that is locked into the muscle cell with the extra energy from carb loading. The only detrimental side of this extra weight is that it can make you feel slow and sluggish at the beginning of your race. However, the extra energy you’ve stored up will definitely pay off near the middle and end of the race!

Something else to think about pre-race is that a low residue diet leading up to race day will also help to minimize the need for bowel movements on race day. That means taking it easy on fibre-rich foods and aiming for low-fibre options, particularly when it comes to grains and cereals.

During the marathon itself, the suggested rate of carbohydrate intake ranges from 60-90 grams per hour. This intake can be in the form of concentrated carbohydrates such as gels/drinks for faster runners but it can also include small amounts of portable foods like boiled potatoes, small pieces of sport bars, dried fruit and rice balls, etc.

Finding your sweet spot for the amount and type of carbohydrate you can tolerate in a race pace situation needs to be done before race day (i.e. in training) so that you know what works for you.

It has been documented in running research that those runners who have prepared a food and fluid strategy AHEAD of the race perform better compared to those who race with no pre-defined plan. So take the time to develop your plan now!

About Beth Mansfield and Peak Performance
Dr. Elizabeth (Beth) Mansfield, PhD, RD is a Registered Dietitian, Sport Nutrition Specialist, and Certified Exercise Physiologist with Peak Performance in Ottawa. Beth educates Canadian athletes on sport nutrition for health and performance.

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