Powers/Dodd - Total Fitness and Wellness, 3/e integrates a strong emphasis on nutrition throughout the text. Good nutrition is essential for developing and maintaining physical fitness and a state of wellness. Learn more about this important interaction between nutrition and exercise by reading the following chapter tips.

Chapter 1

Good Nutrition is Essential to Achieving Physical Fitness and Wellness
Consuming too little of any nutrient can impair physical fitness and potentially result in disease. There for, achieving good nutrition should be a goal of everyone. Although consuming inadequate nutrients increases your risk of disease, consuming too much food energy (overeating) can be problematic as well. Overeating on a regular basis can result in large amounts of fat gain, resulting in obesity. Obesity increases your risk of heart disease and type II diabetes.

Chapter 2

Can the Content of a Pre-exercise Meal Improve the Results of a Fitness Test?
Many manufacturers of "athletic beverages" and "quick energy" candy bars claim that consumption of their products prior to exercise can improve performance. There is no scientific evidence, however, to support the idea that any type of meal eaten before exercise can improve physical performance (you can find out more about this topic in Chapter 14 of Powers/Dodd). In fact, consumption of high volumes of fluid or large solid meals immediately before exercising can negatively impact performance by creating abdominal discomfort. To avoid stomach cramps or other forms of abdominal discomfort during exercise, the pre-exercise meal should be relatively small and eaten at least 2 to 3 hours before exercise. This pre-exercise meal should contain primarily complex carbohydrates (complex sugars such as fruits and breads) and be low in fat. The rationale for this recommendation is based on the fact that carbohydrates are digested rapidly, whereas fat is broken down and absorbed at a slow rate.

Chapter 3

Diet and the Workout Hangover
Can a poor diet contribute to fatigue and over-training? Yes! Failure to consume the recommended amounts of carbohydrates, fats, proteins, vitamins, and minerals can lead to chronic fatigue. Of particular importance to people engaged in a regular exercise training program is dietary carbohydrates. Because heavy exercise uses carbohydrates as a primary fuel source, diets low in carbohydrates can result in a depletion of muscle carbohydrate stores and can lead to a feeling of chronic fatigue. To maintain muscle carbohydrate stores, these nutrients should comprise 60% of the total energy contained in your diet.

Chapter 4

Creatine Monohydrate: A Real Ergogenic Aid?
Recently, many athletes and body builders have begun taking creatine, a supplement that they think will increase muscle mass and endurance. Creatine is a compound synthesized in the body and contained in foods such as meat and fish. It is stored by the body in skeletal muscle and much of it has phosphate added to form phosphocreatine. It is this form, phosphocreatine, that is used to help resynthesize energy (ATP) during short-term, intense exercise. In fact, the depletion of creatine during intense exercise has been shown to be related to the onset of fatigue. Thus., the idea behind supplementation with creatine monohydrate (supplement form for best absorption) is to increase endurance in short-term, intense exercise. Recently, it has been shown that creatine monohydrate does increase total creatine in muscle. In addition, several studies have shown that creatine supplementation enhances endurance during repeated bouts of short-term, intense exercise (bouts lasting less than 20 seconds). Another touted claim of many creatine users is the possibility that creatine increases muscle mass. This possibility has not been thoroughly investigated with scientific studies. Although body weight does increase with creatine supplementation, the likely source of the weight gain is an increase in body water due to the water that is stored with creatine in muscle. In addition, weight gain usually occurs in approximately one week--much too quick for increased muscle protein synthesis. Thus, creatine supplementation may be effective in delaying muscle fatigue during repeated bouts of short-term, intense exercise. However, its effect of increasing muscle mass by increasing muscle protein is unlikely. One important caveat is that the long-term effects of prolonged supplementation with creatine are unknown. Therefore, it would be unwise to use such a substance.

Chapter 5

Do Weight Lifters Need Large Amounts of Protein in Their Diets?
Many of the companies that manufacture nutritional supplements claim that weight lifters require large amounts of protein in their diets to ensure maximal strength gains during training. However, there is no evidence to support this claim. Although a well-balanced diet is essential for anyone engaging in regular weight lifting, research shows that the recommended daily allowance of protein (about one-third gram of protein per pound of body weight per day) is adequate to ensure maximal strength gains. Thus, for people eating balanced diets, a protein supplement during weight training is not recommended.

Chapter 6

When Muscles Cramp
Muscle cramps are one of the most common problems encountered in sports and exercise. For many years the primary causes of muscle cramps were thought to be dehydration and/or an electrolyte imbalances. Accordingly, drinking enough fluids and ensuring that the diet contains sufficient amounts of sodium (from table salt, for example) and potassium (from bananas, for example) have long been encouraged as preventative measures. Whenever muscles cramp, stretching and/or massage have been used to relieve the cramping until the electrolyte balance can be restored.

More recent research, however, suggests that cramping may be due to abnormal spinal control of motor neuron activity, especially when a muscle contracts while shortened. Thus, for example, the cramping that often occurs in the calf muscles of recreational swimmers when their toes are pointed may occur because those calf muscles are contracting while they are shortened.

The most prevalent risk factors for cramps during exercise are muscle fatigue and poor stretching habits (failure to stretch regularly and long enough during each session). Other risk factors include older age, higher body mass index, and a family history of muscle cramps. If cramping occurs you should:

• Passively stretch the muscle. Such stretching induces receptors that sense the stretch to initiate nerve impulses that inhibit muscle stimulation.
• Drink plenty of water in order to avoid dehydration or electrolyte imbalances. Sports drinks can be used to replenish glucose and electrolytes but do not use salt tablets.
• Seek medical attention if multiple muscle groups are involved, because this could be a sign of more serious problems.

Although no proven strategies for preventing muscle cramping during exercise have been proven effective, regular stretching using PNF techniques, correction of muscle balance and posture, and proper training for the exercise activity involved may be beneficial.

Chapter 7

Do Antioxidants Prevent Muscle Injury or Fatigue?
Recent research suggests that the increased muscle metabolism associated with exercise may cause an increase in free radical production. Several studies have shown that this increase in free radicals may contribute to fatigue, and maybe even muscle damage. The obvious question is, "Do active individuals need to increase their consumption of antioxidants?" Several preliminary studies have indicated a positive role for antioxidants, primarily vitamin E, in neutralizing exercise-produced free radicals. In fact, recent reports have demonstrated a reduction in muscle fatigue following administration of antioxidants. Several researchers have suggested that an additional 400 I.U. of vitamin E be consumed daily to protect against free radical damage. However, you should consult your pharmacist or nutritionist before consuming more than the RDA of fat-soluble vitamins. Remember: Fat-soluble vitamins are stored in the body and accumulation may lead to toxicity.

Chapter 8

Obesity Increases the Risk of Disease
Obesity increases the risk for at least 26 diseases. Some of the most serious of these include heart disease, colon cancer, hypertension (high blood pressure), kidney disease, arthritis, and diabetes. For example, obesity increases the risk of heart attack by 60-80%. Further, there is a high correlation between the onset of type II diabetes and body fatness, since over 80% of type II diabetics are obese. Because of the strong link between obesity and disease, the National Institutes of Health concluded that obesity indirectly accounts for 15 to 20% of all deaths in the United States.

The biological link between obesity and a specific disease is not always clear. However, new research has provided direct evidence linking obesity to diabetes via the hormone resistin. Resistin is produced by fat cells and released into the blood. The function of this hormone is to inhibit glucose uptake into cells. Therefore, it is not surprising that individuals that possess a large number of fat cells also have high blood levels of resistin, which inhibits glucose uptake, resulting in high blood glucose (hyperglycemia) and type II diabetes.

Obesity may also contribute to emotional disorders, particularly in adolescents and young adults who are very conscious of their body image. A poor body image resulting from obesity may contribute to low self-esteem and reduce the quality of life.

Chapter 9

Antioxidant Vitamins May Reduce Your Risk of Coronary Heart Disease
New research suggests that antioxidant vitamins (i.e., vitamins E, C, and beta carotene) may reduce your risk of CHD. Specifically, several comprehensive studies have shown that diets high in antioxidant vitamins reduce the risk of arteriosclerosis. The mechanism to explain this observation is reduction by these antioxidants of the buildup of LDL (bad) cholesterol on arterial walls.

While it appears that a diet high in antioxidants may reduce your risk of CHD, the optimal intake of these antioxidant vitamins remains controversial. Most studies showing protective effects of antioxidants have used vitamin supplements at doses above the recommended daily allowances (RDA). This has raised concern by many nutritionists who argue that high doses of these vitamins may result in toxic side effects. Until additional research is performed, the best advice is to eat plenty of fresh fruits and vegetables to obtain as many antioxidants as possible from your diet.

Chapter 10

Can Nutritional Supplements Reduce Emotional Stress?
Because vitamins are good for us, many people feel that the more we get, the better we feel. Because of this prevailing public attitude, many manufacturers have taken advantage of this belief by marketing products that are advertised as "magic bullets" to reduce stress. The fact is that there are no nutritional products that have been proven to reduce emotional stress. Further, because huge amounts of any vitamin could pose health risks, consult your physician or dietitian before deciding to take any nutritional supplements.

Chapter 11

Guidelines for Fluid Intake during Exercise in a Hot Environment
Because the sweat you lose during exercise is replaced with water from the blood, the ultimate danger during prolonged exercise in the heat is the loss of blood volume. The best strategy for preventing a decrease in blood volume is maintaining a regular schedule of fluid intake during exercise. However, thirst for fluid lags behind fluid loss. This is because your body does not recognize a need for fluid until the composition of the blood is changed. Therefore, you should begin to drink within 10 to 20 minutes after beginning exercise before the fluid deficit accumulates. The following fluid replacement schedule will help in meeting your body's needs for water:

• Low in sugar (generally less than 8 grams per 100 ml of water)
• Electrolytes (sodium and potassium)
• Cold (approximately 45-55 degrees)

Fluid intake prior to workout
Drink approximately 200 ml (6 oz) of the fluid 20 to 30 minutes prior to the workout.

Fluid intake during workout
Thirst is a poor gauge of the amount of fluid needed. Drink approximately 100 to 200 ml (3-6.6 ox) every 10 to 20 minutes during exercise, regardless of whether you feel thirsty.

Fluid replacement after workout
In general, you should consume 30 ml (~1 oz) of fluid for every minute of exercise performed. Another means of estimating how much fluid you need is to weigh yourself prior to exercise and immediately after your cool-down period. The difference in body weight is a measure of how much fluid was lost via sweating, and more than that amount should be replaced. In fact, each ounce of body weight lost due to sweating is equivalent to 1 fluid ounce. For example, a pre/postexercise body weight difference of 1 pound indicates that 16 ounces of sweat were lost during exercise. Therefore, consumption of more than 16 fluid ounces (~475 ml) of fluid is required to replace body fluid stores.

Chapter 12

Control of Blood Sugar (Glucose) by Exercise
Carbohydrate is the macronutrient that affects blood glucose levels most dramatically. Both exercise and the hormone insulin act to clear the blood of glucose and get it into the exercising muscle cells. In a nondiabetic individual on a normal diet, there is no concern about blood glucose levels during a normal exercise training session. However, the diabetic individual who is about to begin an exercise training session must be concerned with the type and amount of macronutrients as well as the type and amount of exercise, because the interaction of these factors greatly affects the level of glucose in the blood. Because exercise acts like insulin to clear the blood of glucose, the diabetic individual must learn how different types of exercise affect blood glucose. The diabetic individual who does not understand how exercise affects his or her blood glucose runs the risk of lowering blood glucose to the level at which the individual becomes disoriented, lethargic, and appears to be drunk.

Chapter 13

Does Nutrition Have a Role in Repair of Exercise-Induced Injuries?
There are two aspects of nutrition that may be important to exercise-related injuries. First, when muscle is damaged, the repair systems of the body remove the damaged fibers so that new fibers can grow as replacements. The growth of muscle fibers requires dietary protein to provide amino acids as building blocks for the new fibers. This does not mean that supplemental protein in the diet is necessary for adequate repair to damaged muscle.

The second important aspect is the notion that antioxidants may play a role in minimizing the extent of damage caused by injury. Injury to tissue causes the repair system of the body to release chemicals in the injured area, which may cause inflammation and further destruction to tissue before the rebuilding phase begins. Antioxidants may play a role in preventing this further injury by acting as a scavenger of the free radicals produced during the injury. Although much more research is needed in this area to define nutrition's role in repair of injuries, it is obviously wise to ensure that the RDA of all vitamins and minerals is consumed daily.

Chapter 14

1. Avoid obesity. Sensible eating habits and regular exercise will help you avoid excessive weight gain. Obesity increases your risk of colon, breast, gallbladder, prostate, ovarian, and uterine cancers.
2. Reduce your fat intake. Reduce the intake of total dietary fat to less than 30 % of total calories consumed, and reduce the intake of saturated fat to less than 10% of total calories. A high-fat diet increases your risk of breast, colon, and prostate cancers.
3. Eat more high-fiber foods. Regular consumption of cereals, fresh fruits, and vegetables is recommended. Increasing your fiber intake may reduce your risk of colon cancer.
4. Include foods rich in vitamins A, C, and E in your daily diet. These vitamins may reduce your risk of cancer by removing free radicals.
5. Include cruciferous vegetables in your diet. Research has shown that vegetables such as cabbage, broccoli, brussel sprouts, kohlrabi, and cauliflower may help reduce certain types of cancers. Why these particular vegetables reduce your cancer risk is unclear and continues to be an active area of research.
6. Eat salt-cured, smoked, and nitrate-cured foods in moderation. Numerous studies have reported a high incidence of cancer in people who consume large quantities of these foods.
7. Keep alcohol consumption moderate. High consumption of alcohol increases the risk of cancers of the mouth, larynx, throat, esophagus, and liver.

Chapter 15

Alcohol Abuse and Undernutrition
A common problem associated with chronic alcohol abuse is undernutrition. This occurs due to alcohol's repeated irritation of the gastrointestinal system; the combination of chronic consumption of alcohol and gastric irritation often impairs appetite, which reduces the intake of essential nutrients. The end result is a state of undernutrition, which, in extreme cases, can promote a loss of muscle mass and abnormal functioning of many body organs. The cure for this alcohol-related problem is to seek professional help for alcoholism. In many cases, cessation of alcohol abuse eliminates the alcohol-induced reduction in appetite, and the individual returns to normal eating habits. In severe cases of alcohol-related undernutrition, the nutritional advice of a physician and nutritionist is required.

Chapter 16

Do Nutritional Ergogenic Aids Promote Physical Fitness?
The popular fitness literature is replete with claims that nutritional supplements improve physical fitness and build muscle mass. The following nutritional products are popular supplements that are often used by athletes or fitness enthusiasts:

Do any of these supplements improve physical fitness or performance? The answer is "no" if you are eating a nutritionally balanced diet. Volumes of research clearly show that nutritional supplements do not improve physical fitness in well-fed, healthy individuals.

Click here to find out more about Powers/Dodd - Total Fitness and Wellness, 3/e.