© 2010 pearson education, inc. chapter 16: nutrition and fitness

© 2010 Pearson Education, Inc.

Chapter 16: Nutrition and Fitness


What Is Physical Fitness and Why Is It Important?

Physical fitness is good health or physical condition as a result of exercise and proper nutrition

Physical activity is body movement that expends energy (kilocalories)

Exercise is formalized training or structured physical activity


What Is Physical Fitness and Why Is It Important?

Five basic components of physical fitness which must be considered to achieve optimal fitness• Cardiorespiratory endurance – ability to sustain

cardiorespiratory exercise for an extended period of time• Muscular strength – ability to produce force for a brief

period of time• Muscular endurance – ability to exert force over a long

period of time without fatigue• Flexibility – range of motion around a joint, improved

with stretching• Body composition – the proportion of muscle, fat, water,

and other tissues in the body


What Does a Successful Physical Fitness Program Look Like?

Incorporates activities based on the five components of fitness

Tailored to meet needs of individual


Cardiorespiratory Exercise

Can improve cardiorespiratory endurance and body composition

Cardiorespiratory fitness is measured by VO2max, the maximum amount of oxygen muscles can consume during exercise

• Gradual increases in exercise intensity will help increase VO2max

Cardiorespiratory exercise also helps to maintain a healthy body weight, improves body composition, reduces stress, and reduces risk of heart disease


Strength Training and Stretching

Improve muscle strength, muscle endurance, and body composition

• A low number of repetitions using heavy weights will increase muscle strength

• To increase muscle endurance, perform a high number of repetitions with lighter weights

• Rest between sets of exercises and between workouts to avoid overworking muscles and decrease risk of injury

Stretching can improve flexibility; reduce muscle soreness and risk of injury; and improve balance, posture, and circulation


What Does a Successful Physical Fitness Program Look Like?

The progressive overload principle can help improve fitness over time

• A gradual increase in exercise demands from modifications to the frequency, intensity, time, or type of exercise

• Prevents a plateau of fitness level due to the body adapting to an exercise regimen


Quick Review

A successful fitness program incorporates the five components of fitness

Cardiorespiratory exercise improves cardiorespiratory endurance and body composition

Strength training improves muscle strength and endurance Stretching increases flexibility and reduces risk of injury An effective fitness program can be designed using the

FITT principle The 2008 Physical Activity Guidelines provide

recommendations for duration and intensity of exercise based on individual health goals such as weight management or improved physical fitness

Applying the progressive overload principle helps individuals achieve optimal fitness levels


How Are Carbohydrate, Fat, and Protein Used During Exercise?

Most energy production during cardiorespiratory exercise is aerobic

Anaerobic energy is generated for quick, intense activities that require strength, agility and speed, or a sudden burst of energy.


How Are Carbohydrate, Fat, and Protein Used During Exercise?

During the first few minutes of physical activity, the body relies heavily on anaerobic energy production from ATP and creatine phosphate (PCr)

PCr stored in muscles is depleted after 10 seconds of maximum intensity exercise; stored ATP can only support a few seconds of intense exercise

Once stores are depleted, the body relies on aerobic production of ATP

Figure 16.2

Anaerobic Energy Metabolism


Carbohydrate and Exercise

Carbohydrate is the primary energy source during high-intensity exercise• Obtained from blood glucose and from stored glycogen in

muscles and liver• ~2,000 kcals of energy as carbohydrate is available;

enough to perform 2 hours of moderate-intensity exercise• As intensity of exercise increases, lactate is formed and

can begin to accumulate in muscle tissue- New research suggests it can be an important fuel

during exercise Eat simple carbohydrates during and/or immediately after

exercise• Athletes use carbohydrate loading before competition


Fat and Exercise

Fat (as fatty acids) is the primary energy source during low- to moderate-intensity exercise

• Derived from fatty acids stored in muscle tissue and free fatty acids in the blood from adipose stores

• Use of fat for energy increases throughout the duration of low- to moderate-intensity exercise

• Endurance training increases muscle fatty acid stores which can increase amount of fat used for energy


Protein and Exercise

Protein is primarily needed to build and repair muscle

• Exercise increases cortisol which stimulates protein turnover

• All active people use small amounts of protein for energy

• When kilocalorie intake and carbohydrate stores are insufficient, the body relies on protein

• If protein breakdown exceeds protein synthesis, muscle atrophy can occur

• Most recreational exercisers can easily meet protein needs (0.8 g/kg) with a balanced diet- Endurance athletes and those doing significant

resistance/strength training may need more protein

Figure 16.3

Energy Use During Various Intensities of Exercise


Food Intake and Exercise

The timing of meals affects fitness and athletic performance• Important to allow sufficient time for food to digest

before exercise- Large meals 3–4 hours - Smaller meals 2–3 hours- Liquid supplement or small snack 30 min–1 hour

• Food intake is important to maintain blood glucose supply in exercise lasting greater than 1 hour- Carbohydrate intake recommended at 15–20 min

intervals- 30–60 g of carbohydrate should be consumed per hour

• Food eaten after exercise will affect how the body recovers



Optimal foods before exercise

• 1–4.5 g/kg carbohydrate 1–4 hours prior to exercise

• Consumption of protein and carbohydrate recommended

• High-fat foods should be avoided several hours before exercise

Optimal foods during exercise

• Sports drinks, bars, and gels

• Fructose (fruit sugar) may cause GI distress

• Consuming carbohydrate and protein improves net protein balance for endurance athletes



Optimal foods after exercise

• Consuming carbohydrate after exercise helps to replenish muscle and liver glycogen. It is most effective 30–45 minutes after exercise.

• Consuming protein and carbohydrate after exercise increases muscle protein synthesis

- Low-fat chocolate milk is a low-cost option to provide whey protein and carbohydrate to assist in recovery

• A high-carbohydrate, moderate-protein, low-fat meal should be consumed within 2 hours


Quick Review

Carbohydrate from blood glucose and muscle and liver glycogen are the main source of energy during high-intensity exercise

Fat is the main energy source for low- to moderate-intensity exercise

Protein promotes muscle growth and repair of muscle breakdown caused by exercise

Both the timing of meals and the foods eaten can affect exercise performance and recovery time


Vitamins and Minerals in Fitness

Intense, prolonged exercise increases production of free radicals

• Antioxidants such as vitamins E and C protect cells from the damage of free radicals

• Research has not shown that supplementation above the RDA improves athletic performance or decreases oxidative stress

Unless the body is deficient in a nutrient, vitamin and mineral supplements will not improve athletic performance


Vitamins and Minerals in Fitness

Certain minerals may be a concern in highly active people

• Iron

- Necessary for energy metabolism and oxygen transport

- Levels may be low due to menstruation in women, intravascular hemolysis, or sports anemia

• Calcium

- Lost in sweat, thus losses may be high in athletes

- Supplementation not recommended unless intake from food and beverage is inadequate to meet the RDA


Quick Review

Antioxidants such as vitamins E and C are thought to protect cells from free radical damage though research has not shown that supplementation is beneficial to athletes

Certain minerals may be a concern to athletes including calcium and iron

Adequate amounts of nutrients can be consumed in foods, so supplementation is usually not necessary

Anyone should consult a physician or Registered Dietitian before taking dietary supplements


How Does Fluid Intake Affect Fitness?

Consuming adequate fluid during exercise is essential for preventing dehydration and promoting optimal performance

During exercise, the body loses water and electrolytes (sodium, chloride, and potassium) in sweat

• In hot, humid weather sweat may not evaporate and risk of hyperthermia increases

• Cold weather, especially if wet, can contribute to hypothermia

• The body sweats when exercising both in hot and cold weather, so meeting fluid needs is always a concern



Fluids are needed before, during, and after exercise

• Healthy adult women require 9 cups water/day

• Healthy adult men require 13 cups water/day

• To determine fluid needs for exercise

- Weigh yourself before and after exercise

- Consume 16–24 ounces of fluid for every pound of body weight lost during exercise



Sports drinks contain 6–8% carbohydrate and sodium and potassium

• Most beneficial for exercise lasting longer than 60 minutes

Certain beverages are suboptimal for hydration during physical activity

• Juice and juice drinks

• Carbonated drinks

• Alcohol

• Caffeine

Figure 16.4

Effects of Dehydration on Exercise Performance



Consuming too little or too much fluid can be harmful

Too little fluid

• To prevent acute dehydration follow a regimented hydration schedule before, during, and after exercise

• Chronic dehydration is due to inadequate fluid consumption over a long period of time and may be indicated by very dark urine and infrequent bathroom trips



To much fluid

• Taking in too much water without sufficient electrolytes can dilute the blood and cause hyponatremia

- Symptoms of hyponatremia include rapid weight gain, nausea, vomiting, swollen hands and feet, headache, dizziness, and confusion


Quick Review

Adequate hydration before, during, and after exercise is important to sustain fluid and electrolyte balance and normal body temperature

Consuming too little or too much fluid can be harmful and impair performance

Water is the preferred beverage for hydration, but sports drinks can be beneficial during moderate- or vigorous-intensity exercise of a longer duration


Can Dietary Supplements Contribute to Fitness?

An ergogenic aid is any substance that is used to improve athletic performance

Most commonly used aids include

• Creatine

• Caffeine

• Anabolic steroids

• Growth hormone

• Erythropoietin


Creatine

Improves athletic performance in high-intensity, short-duration activities such as weight training

Shown to increase muscle strength and muscle mass No negative effects on blood pressure, kidney, or liver

function in healthy people


Caffeine

Stimulates the central nervous system and decreases perception of effort

• May increase metabolism of fatty acids for energy and spare glycogen stores

Enhances athletic performance during endurance events NCAA classifies as a banned substance when urine

concentrations exceed 15 micrograms per milliliter


Anabolic Steroids

Testosterone-based substances that promote muscle strength and development

Many negative side effects including

• Impotence in men

• Amenorrhea in women

• Changes in hair growth

• Extreme mood swings and aggressiveness Use is prohibited by most professional agencies


Growth Hormone

Increases protein synthesis, causing an increase in muscle mass but not strength

• Could impair performance by reducing power, speed, and endurance

Decreases glycogen breakdown and increases the use of fatty acids for energy which can decrease body fat

Abuse of growth hormone can lead to development of diabetes, atherosclerosis, hypertension, or acromegaly


Erythropoietin

Hormone produced by the kidneys that stimulates synthesis of red blood cells

• Synthetic versions used to increase oxygen carrying capacity of blood

Synthetic erythropoietin is a banned substance in most athletic organizations

• Blood doping (red blood cell reinfusion) is an older method used to increase oxygen-carrying capacity of blood

• Both blood doping and synthetic erythropoietin increase blood viscosity and could cause stroke or heart attack


Meal Replacements

Sports bars and shakes are not defined as dietary supplements by the FDA

• Main energy source is carbohydrate with some protein and fat

• Offer convenience, but are often expensive

• Should not replace whole, nutritious foods in the diet


Quick Review

Dietary supplement and ergogenic aids such as creatine, caffeine, anabolic steroids, growth hormone, erythropoietin and blood doping, may enhance performance, but can have serious side effects

Sports bars and shakes are convenient energy sources, but can be costly and should only be included as a minor part of an overall healthy diet


Putting It All Together

Cardiorespiratory endurance, muscle strength, muscle endurance, flexibility, and body composition are the components of fitness

Effective conditioning programs can be designed using the FITT and progressive overload principles

Both the timing of meals and the foods eaten can affect exercise performance and recovery time

Certain vitamins and minerals are a concern to athletes; supplementation is not usually necessary as adequate amounts can generally be consumed in foods

Sports drinks may be beneficial for moderate to vigorous activities or endurance sports

Dietary supplements and ergogenic aids may enhance performance, but can have negative side effects

© 2010 pearson education, inc. chapter 16: nutrition and fitness

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