In and Out

American Fitness, Nov, 1999 by Nancy Clark

The latest research from the American College of Sports Medicine (ACSM) reinforces the correlation between proper nutritional intake and optimal physical performance.

At the annual meeting of the American College of Sports Medicine (ACSM) in Seattle, Washington, on June 2-5, 1999, exercise scientists presented a plethora of research regarding the latest sports nutrition news.

Exercise and Appetite

According to Neil King, an exercise scientist from England, a weak link exists between exercise and appetite. That is, the average person who performs additional exercise does not significantly increase caloric intake. Why? King surmises they are simply less active the rest of the day, thus conserving calories.

King regards exercise as a demanding way to lose weight. You may spend an hour exercising off 600 calories, but they can easily be replaced in six minutes. Furthermore, after exercise you may eat for reasons other than hunger, such as self-reward for training vigorously.

Body Fat

A large variance occurs among methods of' measuring body fat. In 10 competitive, 30-year-old male runners, body. fat quantities ranged from 10 5 percent with DEXA (a highly accurate method used primarily in research facilities), 9 percent with underwater weighing, 8.5 percent with skin fold calipers and 6 percent with bioelectrictrial impedance.

Despite popular belief, restricting dietary fat may not contribute to loss of body fat. Women who ate little or no fat had the same body fat as those who ate more fat and calories. Both groups exercised for one or more hours per days a week.

Caloric Expenditure

If you are interested in learning about caloric expenditure rates during exercise, here are some samples:

* Collegiate female soccer players burn about 1,000 calories per game, expending more in the first half.

* Women (25 years old, 135 pounds) burn about 200 to 250 calories per hour of light to moderate free weight circuit training.

* Women who participated in strength training for 100 minutes have a 4 percent higher resting metabolic rate 15 hours after the exercise session. This "afterburn" can aid in losing fat.

* Men who weighed 150 pounds burned about four to five calories per minute of moderate exercise on an elliptical trainer. (Note: This was about 40 percent to 80 percent less when calculated by the machine.)

Compulsive Exercise

Over-exercising can be a problem for some athletes, causing increased fatigue and feelings of heaviness due to staleness. However, these people tend to continue training, even though they need rest. Why? Exercise is often driven by the desire to try to change a poor body image. For example, among, a group of 148 fitness instructors, 44 percent were obligatory exercisers with a strong drive for thinness. Exercise alone won't totally reshape a body.

Performance

Exercise scientists continue to search for ways to improve performance. Here are some tips:

* Because depletion of carbohydrates is associated with fatigue, this question arises: If you adapt your body to preferentially burn fat by eating a high fat diet, will you be able to exercise longer? Australian sports nutritionist Louise Burke reports no clear benefits to this "fat loading" theory. She had athletes eat a high fat diet for five days, then carbo-load and rest the day before the exercise test. Only two of the eight cyclists performed significantly better during the two hours of hard cycling followed by a time trial (during which they took in only water, but no carbs). Burke recommends consuming carbs during exercise as a better way to enhance performance than "fat loading."

* Don't over-eat pre-exercise fat. Subjects given 760 calories from a high fat meal three hours before exercise were 14 percent slower than when they ate pre-exercise carbohydrates.

* Consuming adequate water and carbohydrates during endurance exercise delays fatigue. However, you'll still experience fatigue even if you maintain normal hydration and blood sugar levels.

* Taking 200 calories of carbs in gel form or as a beverage makes little difference. Both have similar effects upon blood glucose.

* To help delay fatigue during exercise in hot weather, try pre-cooling your body with a cold bath or shower. Fatigue occurs when the body temperature reaches 103.5 [degrees] F.

* Your body needs/uses carbs consumed during exercise. A sports drink provides about 25 percent of the calories burned during two hours of moderate cycling.

* Sports drinks taken before and during intermittent high intensity exercise, such as basketball or soccer, can delay fatigue and enhance mental function. Drink well!

* Sports drinks consumed even five minutes prior to intense sprinting get absorbed from the stomach. Eighty percent of Gatorade got absorbed during 40 minutes of intense sprinting, as compared to 90 percent at rest.

* Carbo-loading is not essential for endurance athletes such as cyclists racing for 100 kilometers (62 miles) if they consume carbs during the exercise. Seven cyclists consumed either a moderate carbohydrate intake prior to the race and started off with lower glycogen stores or a high carbohydrate intake. Two hours before the exercise test, each cyclist ate about 600 calories of carbohydrates. During the test, each consumed about 300 calories of carbs. Both groups performed equally well. The fuel intake before and during exercise compensated for the lack of carbo-loading.