Nutritional Needs for Exercise

Of the six basic nutrients needed for a healthy body (water, carbohydrates, protein, fat, vitamins, minerals), water is the most important when it comes to exercising. Even though water provides no energy, it is essential for the proper functioning of muscles and regulation of body temperature. Maintaining adequate hydration (water stores), especially while exercising, is key to top performance. Helpful means of doing this include: drinking water on a regular basis before, during and after exercising; drinking fluid during exercise before you are thirsty; drinking enough fluids to keep your urine clear, and replacing weight loss during exercise with an equal amount of fluid (one pound = one pint of fluid).

Carbohydrates and fat are the primary energy sources used while exercising. Fat provides nine calories per gram and is used during low level activity. Carbohydrates contain four calories per gram and is the energy source preferred by muscle and the brain during active exercise. The majority (60 percent) of your daily caloric intake should come from carbohydrates, and only 25-30 percent of your calories from fat.

Protein is composed of amino acid building blocks and is important in building and repairing muscle. Protein is a source of calories (four calories per gram), but is a poor choice as an energy source because of the extra water needed to eliminate the nitrogen waste.

Vitamins and minerals do not provide energy but are essential in regulating chemical reactions within the body and to help form structures of the body (such as calcium in bones). Almost all vitamins and minerals needed for a healthy body can be obtained by eating a variety of wholesome, natural foods. Rarely are supplements necessary or helpful.

 

Sports drinks

Water is still the best sport drink for recreational athletes who exercise for less than 60 minutes. It is inexpensive, readily available and does an excellent job of replacing sweat losses. For athletes who exercise longer than 60 minutes, drinking a dilute sugar solution while exercising will provide fuel to allow you to exercise longer. Commercial sports drinks contain 50-80 calories per eight ounces, which is the concentration of sugar best absorbed by the stomach during exercise. Fruit juices and soft drinks can also provide energy while exercising, but they should be diluted in half to prevent interfering with fluid absorption from the stomach. Remember that maintaining hydration is the most important performance enhancer. Drinking sports drinks while exercising is analogues to adding gas to your car while driving. The extra gasoline will allow you to go farther, but not faster.

After exercising it is important to replenish your glycogen (sugar) stores. This is most effectively done within the first two hours after exercising. You should try to consume 0.5 grams of carbohydrates per pound of body weight as soon as possible after exercising. The high calorie sports drinks can be helpful for this as they are easy to consume and digest just after a workout. However, in spite of all the hype and advertising, none of the sport drinks are more effective than water and high carbohydrate foods at helping you to recover from a workout or prepare for the next one.

Creatine: Does it boost performance?

Creatine monohydrate is a naturally occurring substance, present in milk, red meat, pork, and some fish (tuna and salmon). It is used by the body to provide high energy phosphate (ATP) to the muscles. ATP is the actual energy form used by muscles for muscle contraction. Your body requires approximately two grams of creatine per day. This is produced by the liver and kidneys if your daily intake is too low, therefore it is not considered an essential nutrient. Studies have shown that by consuming 20 grams of creatine per day for five days (loading dose), then continuing a maintenance dose of five grams per day, you can increase your creatine stores by more than 20 %. There are some recent studies, however, suggesting that a loading dose may not be necessary and that the maintenance dose of 5 grams/day is enough for the desired effect. Cycling the intake of creatine supplements isn't necessary, nor does it make sense since it is an energy buffer, not a hormone. It was originally thought that a high carbohydrate diet would potentiate the effect of creatine (via the insulin pathway) however further analysis suggests this would require such high, non-physiologic quantities that it isn't feasible.

Increase in creatine stores can enhance your ability to perform repeated bouts of high intensity, short duration activity. Numerous studies have shown that creatine supplementation does not improve longer duration aerobic-type exercise. Thus, it may be beneficial for use by power lifters and sprinters, but not long distance runners or cyclists. Creatine may enhance the muscular changes associated with resistance weight training presumably because of an increased ability to train more intensely.

Side effects include muscle cramps, mild GI distress, and nausea all of which resolve within a month of discontinuing the supplement. Body mass increases from 1 to 3 lbs. after one week of supplementation with at least some of the weight gain due to increased water absorption (both intracellular and extracellular). There are no long term studies on the use and risks associated with creatine supplementation so it's unclear how safe it is.

Currently creatine monohydrate use is allowed by the USOC and IOC.

 

References

Kraemer, Wm. J., Ph.D., and Volek, Jeff.  S., M.S., R.D.. Creatine supplementation. Current Comment, American College of Sports Medicine, June, 1998.

Volek, Jeff S., M.S., R.D.. Creatine supplementation: possible role in improving exercise performance. ACSM Health & Fitness J. 1(4):23-29, 1997.