Smart Eating Beats Fatigue

PHOTO BY MARGARITA ZUEVA ON UNSPLASH

How can I get more energy?

Endurance athletes are by nature high-energy people. Logging miles before most people have turned on the coffee pot; their weekends are spent doing sports, not watching them.

Despite an innate love of being active, the obligations of everyday living can leave even the most motivated athlete feeling overwhelmed and fatigued. Diet can make a difference. Here’s how.

Types of Fatigue
“Fatigue is anything that leads to a decrease in performance.” – Mark Davis, PhD, Dept of Exercise Science, University of South Carolina, Gatorade Sports Science Conference, July 2005

As a sport nutritionist, I often get questions about diet and fatigue. Typically, I need to clarify what kind of fatigue is the problem and then try to match dietary interventions to resolve the situation. Usually, complaints of fatigue fall into three general categories: 1) overall low energy, including tasks of daily living and motivation to go out and train, 2) inability to go to 100% during interval training or racing, and 3) early muscular fatigue and poor recovery. Of course, sometimes an athlete will be experiencing all three types of fatigue at the same time. As important as diet is to performance, underlying health problems are always a possibility. When fatigue is prolonged and severe, it is important to be evaluated by a physician familiar with endurance training.

For many athletes, nutrition is a topic of conversation but somehow that conversation is never translated into actual food choices. Deadlines at work, kid’s soccer games, and running errands push food purchasing and preparation to the low end of the priority list. Unfortunately, when hunger pangs strike—as they do every day—a quick pickup meal may be the result. Is fast food such a bad thing? Or what about a meal that is missed completely?

Overall Energy

Random meals can result in low energy level for two reasons: 1) missed meals lead to eating a calorie and fat “load” later in the day, and 2) restaurant food tends to be high in fat. Researchers at the University of Maryland Department of Medicine have shown that a single high-fat meal (50g fat, 55g carb, 30g protein) delivers a double whammy when it comes to health. First, a “fat load” stimulates a vasoconstrictive response, reducing blood flow through an artery by as much as 10% for three to four hours after eating. That means less oxygen will be available to working muscles. Second, in the three to four hours following a high fat meal markers of oxidative damage increase, indicating damage to arteries. This is not a good thing for athletes who rely on their heart and vascular system for maximum performance. What does a 50g fat meal look like on the table? Here are just a couple of artery-damaging examples: Taco Bell Nacho Mucho Grande, 1320 calories and 82g fat; or Subway Meatball sub with cheese, a bag of chips, and two M&M cookies for 1109 calories and 56g fat. Home meals can be just as bad if missed meals lead to gorging: a heaping plate of spaghetti and meatballs, with garlic bread, salad and Italian dressing can hit 1000 calories and 50+ grams of fat very easily.

What is a good strategy for improving overall energy? Here are some suggestions: 1) have a plan for the day’s meals, 2) have a back-up plan, 3) learn which foods from restaurants are lowest in fat, and keep fat intake per meal below 40 grams, 4) go no longer than 5 hours between meals. Aim to select at least one-half of carbohydrate choices from whole grains, which have a lower glycemic index than processed grains.

Energy to Go 110%

During exercise, central nervous system fatigue—or “central fatigue”—develops in the brain because of changes in the level of certain neurotransmitters. These neurotransmitters, which act as chemical messengers, control the initiation of voluntary muscle movement, muscular coordination, motivation, concentration, problem solving ability, perception of effort, and level of alertness. Since the brain is the central switchboard for all thoughts, it also controls the initiation of voluntary movement in the muscle. Once central fatigue develops, every task takes more effort to initiate and physical movement is less coordinated.

In an event lasting over three hours, central fatigue can lead to errors in judgment, clumsy transitions, and a decrease in mental toughness. Exactly what triggers the neurochemical changes that cause central fatigue is still a matter of debate, however, research done by the U.S. Army has demonstrated that carbohydrate plus caffeine improves thinking ability and endurance performance. How much carbohydrate and how often to take it depends on the duration and intensity of exercise. What is a good strategy for minimizing central fatigue during a long event? Plan on 30-60 grams of a high glycemic index carbohydrate (sport gel or block) every 60 minutes, taken with water. Use a sport hydration drink that includes a mixture of carbohydrate sources (maltodextrin, brown rice syrup, glycose polymers, fructose) for maximum delivery of oxidizable energy. Caffeine at low doses (100mg) will decrease the perception of fatigue and improve concentration and coordination. Because of a wide variance in toleration to caffeine, athletes should experiment with its use in a non-race situation.

Peripheral Muscular Fatigue

An important muscle that often gets overlooked is the one in your head. Many people do not realize that one of the biggest users of glucose (or sugar) in the body is the brain. On the average, the brain burns up about 150 grams of glucose per day. That’s equivalent to 900 calories. Fortunately, the brain is able to use alternative fuel sources such as the breakdown of protein and ketones, and it runs most efficiently on glucose obtained from carbohydrates. Although the brain isn’t doing any actual physical work during exercise, it does call the shots when it comes to initiating voluntary movement in peripheral muscles.

Peripheral fatigue is fatigue that occurs due to metabolic changes within the muscles that are powering physical activity. When your legs, arms, and back are depleted of nutrients and fuel they can no longer function, even if you have the desire. There is absolutely nothing left; you can’t go on.

The fuel, or energy, to draw upon for muscular work during intense exercise like running is primarily glycogen which is the storage form of carbohydrate within the muscles and liver. In humans, glycogen storage is limited to about 1,500 calories, enough to power about two hours of hard exercise. Fat stores, on the other hand, are much higher. Even in lean individuals, fat can supply about 30,000 calories of fuel.

Exercises performed at low intensity, for example, balancing on a sled or easy pedaling, do not use up glycogen stores as rapidly as running because the body is able to burn fat as well as carbohydrate when the heart rate is lower. However, even at low intensity, after three to four hours of continuous activity muscle glycogen stores become greatly reduced, and the liver begins to break down its stores of glycogen in an effort to maintain blood glucose levels. Eventually liver glycogen becomes depleted also, and blood sugar drops. At this point, an athlete will feel exhausted and cease exercising unless additional carbohydrate is eaten.

Consuming a diet that has 50 percent to 70 percent carbohydrate is the best way to maintain glycogen stores when training on back-to-back days.

What foods are the best sources of carbohydrate for beating fatigue? Look for foods that provide these characteristics:

1. Low glycemic load: these carbohydrates provide sustained energy. The glycemic load (GL) is a ranking system for carbohydrate content in food portions based on their glycemic index (GI) and the portion size. For example, a 100 g portion of watermelon (GI 72) has a carb content of 5g (because of its high water content). The GL is calculated as 5 x .72=3.6, which is low. For a complete table of GL, go to www.ajcn.org/cgi/content.

2. High anti-oxidant: these protect the vascular system in the brain and provide carbohydrate for energy.

3. Low saturated and trans-fat free carbo-snacks: many carbohydrates are “packaged” with unhealthy fat. Use snack foods and baked goods that are made with flax seed oil, olive oil, or polyunsaturated vegetable oils.

For every endurance athlete, maintaining energy for physical and mental work should be part of an overall training program. Taking the time to plan out menus and shopping lists, and learning food preparation techniques can make the difference when it comes to achieving performance goals.

Smart High Energy Foods

“Everyday” eating: low GL, high carbohydrate content

  • Oatmeal
  • Whole grain cold cereal, crackers
  • All-bran cereals
  • Fettuccini (egg)
  • Whole grain pasta
  • Barilla Plus High Protein pasta
  • Whole grain bread
  • Legumes
  • Low fat dairy or soy milk & yogurt
  • Watermelon
  • Oranges & grapefruit
  • Carrots, tomatoes

“High intensity exercise” foods: high GL, high carb, low fat, and mixed sugars

  • Sports drinks
  • Sport gels and blocks
  • White bread
  • Graham crackers
  • Fruit drink
  • Pretzels & saltines

Donna Marlor, RD, BSN, MA

 

 

 

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