fitness exam 3

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Physical Fitness: Concepts and Benefits

Definition and Importance

Physical fitness is the ability to perform physical activities requiring cardiorespiratory endurance, muscle endurance, strength, and/or flexibility. Achieving physical fitness requires both regular physical activity and adequate nutrition.

Physical Activity: Voluntary movement resulting in energy expenditure (burning calories). Examples: gardening, walking the dog, playing with children.
Exercise: Structured or planned physical activity. Examples: step aerobics, running, weight lifting.

Both terms are often used interchangeably. Optimal fitness requires attention to both activity and diet.

Benefits of Physical Fitness

Improved sleep quality
Enhanced nutritional health
Better body composition
Increased bone density
Resistance to infectious diseases
Lower risk of cardiovascular disease and type 2 diabetes
Stronger self-image
Improved immune system
Reduced depression and anxiety
Longer life expectancy and improved quality of life

Components of Physical Fitness

Five Basic Components

Cardiorespiratory Endurance: Ability to sustain prolonged exercise (e.g., running, biking). Requires efficient oxygen and energy delivery by cardiovascular and respiratory systems.
Muscular Strength: Greatest amount of force exerted by a muscle at one time.
Muscular Endurance: Ability of muscle to produce prolonged effort without fatigue.
Flexibility: Joints’ ability to move freely through a full and normal range of motion. Enhanced by stretching; reduces injury risk.
Body Composition: Relative proportion of muscle, fat, water, and other tissues. Muscle is denser than fat; body composition can change without total body weight changing.

Physical Activity Guidelines

Type of Activity	Frequency	Intensity	Duration	Examples
Cardiorespiratory	3-5 days/week	Moderate to vigorous	20-60 min/session	Running, cycling, swimming
Strength	2-3 days/week	Enough to fatigue muscles	8-12 reps/muscle group	Weight lifting, resistance bands
Flexibility	2-3 days/week	Stretch to slight discomfort	10-30 sec/stretch	Yoga, static stretching

Developing Fitness and Preventing Injury

Body Adaptations

Physical activity overload leads to structural adaptations supporting the activity.
Muscle hypertrophy occurs when protein synthesis exceeds degradation.
Atrophy occurs when protein degradation exceeds synthesis.

Strategies

Be active all week
Use proper equipment and attire
Include warm-up and cool-down activities
Challenge strength and endurance regularly
Pay attention to body signals
Include at least one rest day per week

Energy Systems in Physical Activity

Main Energy Systems

Phosphagen System: Uses creatine phosphate for immediate energy (short, intense bursts).
Lactic Acid System: Anaerobic glycolysis; produces ATP and lactate for short-term, high-intensity activity.
Aerobic System: Uses aerobic glycolysis, fatty acid oxidation, and TCA cycle for sustained, moderate-intensity activity.

Activity Intensity	Duration	Energy System	Preferred Fuel Source	Oxygen Needed?	Activity Example
Very High	1-10 sec	Phosphagen	ATP-CP	No	Shot put, sprint
High	20 sec-2 min	Lactic Acid	ATP from carbohydrate	No	400m run
Moderate	>2 min	Aerobic	ATP from fat and carbohydrate	Yes	Jogging, cycling

Energy Metabolism Equations

Macronutrients and Exercise

Carbohydrates

Primary energy source during high-intensity exercise.
Stored as glycogen in muscle and liver; about 2000 kcal available (enough for ~20 miles running).
Depletion leads to muscle fatigue.
High-intensity activities use more glycogen; higher carbohydrate diets increase glycogen stores.
Liver glycogen maintains blood glucose; lactic acid produced at high intensities.

Carbohydrate Loading

Days Prior	Activity	Carbohydrate Intake
4-6 days	Taper exercise	4-6 g/kg/day
1-3 days	Taper exercise	10 g/kg/day
Competition day	Eat 3-4 hours before	250-300 g

Fat

Primary energy source during low-intensity exercise.
Two forms: fatty acids from triglycerides in adipose and muscle tissue.
25-30% of calories should come from fat; focus on unsaturated fats.
Well-trained muscles burn more fat; moderate-intensity exercise uses fatty acids from muscle triglycerides.

Protein

Needed to build and repair muscle; not a major fuel source.
Amino acids promote muscle growth and recovery.
Endurance athletes: 1.2-1.4 g/kg body weight; resistance/strength athletes: 1.6-1.7 g/kg body weight.
Body prefers carbohydrate and fat for energy; amino acids can be converted to glucose.

Nutrition Timing and Performance

Pre-Exercise Nutrition

1-4.5 g carbohydrate/kg body weight, 1-4 hours before exercise.
Carbohydrate 15-30 min before: immediate energy, spares glycogen, reduces muscle damage.
Protein before and during exercise increases muscle glycogen synthesis and protein synthesis after exercise.
Avoid high-fat foods before exercise.

During Exercise

For exercise >1 hour: begin carbohydrate intake shortly after start and every 15-20 min (30-60 g/hour).
Best choices: glucose, sucrose, maltodextrin (quick absorption).
Consuming both carbohydrate and protein is best for muscle maintenance and growth.

Post-Exercise Nutrition

Carbohydrate:protein ratio of 3:1 promotes muscle glycogen and protein synthesis, faster recovery.
Preferred protein: whey (in milk) – rapid absorption, all essential amino acids.
Consume high-carbohydrate, moderate-protein, low-fat meal within 2 hours after exercise.

Vitamins, Minerals, and Fluid Balance

Role in Fitness

Vitamins and minerals are essential for metabolism of carbohydrates, fats, and proteins during exercise.
Act as antioxidants, protecting cells from oxidative stress.
Supplements generally not necessary; nutrient-dense foods preferred.

Key Minerals

Iron: Low levels reduce hemoglobin and oxygen transport, causing fatigue. Female athletes at higher risk for deficiency.
Sports anemia: Temporary decrease in hemoglobin from increased blood volume; self-correcting.
Calcium: Reduces risk of bone fractures; lost in sweat. Supplements only if dietary intake is inadequate.

Fluid and Electrolyte Balance

Exercise increases loss of water (sweat, exhalation) and electrolytes (sodium, chloride, potassium).
Dehydration impairs performance; loss of 2% body weight reduces muscle capacity.
Electrolyte imbalance can cause cramps, nausea, headache, and edema.
Evaporation of sweat cools the body; hot, humid weather increases risk of heat exhaustion and heat stroke.

Heat Exhaustion	Heat Stroke
Profuse sweating, fatigue, thirst, muscle cramps, headache, dizziness, weakness, nausea, cool/moist skin	Extremely high body temperature (>103°F), red/hot/dry skin, rapid pulse, shallow breathing, throbbing headache, dizziness, nausea, confusion, unconsciousness

Hydration Recommendations (ACSM)

When?	How Much?
2-3 hours before exercise	14-22 fluid ounces (2-3 cups)
5-10 minutes before exercise	4-8 fluid ounces (0.5-1 cup)
15-20 min intervals after exercise begins	6-12 fluid ounces (0.75-1.5 cups)

Dietary Supplements and Ergogenic Aids

Supplements

Deficiencies impede performance; athletes with low food intake may benefit from multivitamin-mineral supplements.
Supplements do not improve performance in well-nourished athletes.
Antioxidants (vitamins C and E) may decrease oxidative stress in highly trained athletes.

Ergogenic Aids

Substances used to enhance athletic performance (e.g., creatine, caffeine, anabolic steroids, growth hormone).
Creatine: May improve high-intensity, short-duration activities.
Caffeine: Enhances endurance and high-intensity performance; banned by some organizations.
Anabolic Steroids: Promote muscle growth and strength; serious health risks.
Growth Hormone: Reduces body fat, not muscle strength; can cause serious health issues.

Summary Table: Macronutrient Needs for Athletes

Macronutrient	Endurance Athletes	Strength Athletes
Carbohydrate	6-10 g/kg body weight	5-7 g/kg body weight
Protein	1.2-1.4 g/kg body weight	1.6-1.7 g/kg body weight
Fat	20-35% total calories	20-35% total calories

Key Takeaways

Physical fitness is multifaceted, requiring attention to activity, nutrition, and recovery.
Macronutrient and fluid needs vary by activity type, intensity, and duration.
Vitamins and minerals are essential for energy metabolism but supplements are rarely needed if diet is adequate.
Proper hydration and electrolyte balance are critical for performance and safety.
Dietary supplements and ergogenic aids should be used with caution and only when necessary.