Blog Posts From Active Expert: Nancy Clark RD CSSD Tagged With intestines

Fueling During Endurance Exercise

guest — Tue, 04 May 2010 20:07:18 GMT

How can you maintain good energy when you’re exercising for longer than 60 to 90 minutes? By eating enough calories of foods that settle well…!

The standard recommendation for fueling during endurance exercise has been to target 1 gram of carbohydrate per minute of exercise (60 grams of carb per hour, the equivalent of 240 calories for a 150 pound athlete). The research, originally done with just glucose, indicated consuming more than 60 grams of glucose per hour offered no additional benefits. The body has a limited number of glucose transporters and can carry only 60 grams out of the intestines, into the blood stream and to the muscles.

Recent research indicates consuming a variety of sugars (that is, more than just glucose) allows more fuel to become available per hour. That's because different types of sugars (carbs) use different transporters. Generally, athletes consume more than just glucose. (Sports drinks, for example, tend to be glucose+fructose.) Let's say you eat a banana that consists of many different types of sugars and uses many different transporters. Your muscles will have access to more fuel (up to 90 g carb/hour; 360 calories) than if you consume just one kind of sugar (as might happen with some engineered foods).

Variety is a wise idea—as is practicing yoru fueling during long training sessions so you can learn what works best for your body. Some people like engineered sports candy and gels, others prefer dried pineapple and gummy candy. Take your choice--just experiment during training to determine if 200 to 300 calories per hour is the right amount for your body.

Missing Link: pre-exercise food

guest — Tue, 29 Jul 2008 11:46:15 GMT

Too many people who exercise purposefully do not eat before they exercise. They think they should exercise on empty, to prevent intestinal distress. While this may be OK for a short bout of exercise, when they build up to an hour of more of exercise, they start to run out of energy. Thye experience needless fatigue.

Research indicates consuming 100 to 300 calories (depending on your body size and how hard you will be exercising) within the hour before you exercise can improve performance -- to say nothing of enjoyment of the the session. Hence, if you have been avoiding food out of fear of "rapid transit", you should start to train your intestinal track to lean how to digest food while you exercise. This is important if you plan to workout for more than an hour. Start with a saltine, apretsel, a bite of banana, and work up to two saltines, two pretzels, two bites of banana ... With time, your intestinal track will adjust to digesting food while you exercise, and you'll have better, stronger, more enjoyable workouts.

Training your intestinal track as well as your heart, lungs and muscles is important if you plan to do workouts that last longer than one hour!

Nancy Clark MS RD CSSD

Fueling for long runs

guest — Thu, 24 Jul 2008 18:38:21 GMT

“Oh, I didn’t know I could eat candy or regular food” commented the novice marathoner. She was training for her first 26.2 mile event, and was barely able to complete the first 10 miles. She was afraid to eat before she trained, fearing the food would talk back to her. No wonder she was running out of energy! She needed to fuel her body better. This would mean training her intestinal tract to tolerate food and fluids.

During the runs, she drank just water because the one time she had tried a gel, it upset her intestinal tract. I asked if she had tried gummy bears, hard candies, twizzlers, or peppermint patties. She hadn’t even thought about those options. She had limited herself to the engineered sports foods that she’d seen advertised abundantly in running magazines. I invited her to experiment with standard foods to which her body was accustomed. She started with small nibbles pre-run – a saltine cracker, a pretzel, a chunk of banana. She then added bigger portions as her body got used to the pre-run fuel.

During her long runs, when she began to run out of energy, I suggested she try some sugary candy. Starbursts became her favorite way to consume the energy she needed to enjoy miles of training. By targeting about 200 calories per hour (after the first hour of running), she was able to maintain high energy during the long runs. She experimented with lots of food options, and found that she better enjoyed standard foods than the engineered products.

Give food a try? For more information, see my Food Guide for Marathoners: Tips for Everyday Champions.

Nancy Clark MS RD