Introduction to Exercise Physiology

Introduction to Fuel for Exercise

  • Discuss the concept of fuel for exercise in exercise physiology.

  • Importance of proper nutrition for workout performance.

Types of Fuels for Exercise

Macronutrients

  • Major nutrients that serve as fuel sources:

    • Carbohydrates

    • Proteins

    • Fats

  • These nutrients are the only components in food, commonly referred to as macronutrients.

Definitions

  • Substrate: A term used synonymously with fuel, defined as sources from which energy is made.

    • Important understanding in energy production, acts as a substrate for exercise performance.

Energy Currency

ATP (Adenosine Triphosphate)

  • Described as the currency of energy in the body.

    • ATP is the common language that all cells understand.

    • Derived from the breakdown of food sources like pizza and pasta.

    • Structure:

    • High energy molecule composed of adenine bonded to three phosphate groups.

    • Required for muscle contraction and overall cellular function.

Overview of Macronutrients

Carbohydrates

  • Essential for exercise; they act as energy sources.

  • Relationship with fats:

    • Fats are associated with storage and survival.

  • Excess carbohydrates convert to fats when stores are depleted.

  • Proteins play a structural role, building muscle and tissue.

Definition of Macronutrients vs. Micronutrients

  • Macronutrients: Consumed in large quantities (grams) for energy.

  • Micronutrients: Required in smaller quantities (milligrams or micrograms).

    • Examples include vitamins (A, B, C, D, E) and minerals (iron, calcium, magnesium, selenium, and zinc).

Bioenergetics

  • Definition: Process of converting substrates into energy (ATP).

  • Occurs at the cellular level and is essential for metabolic activities.

Metabolism

  • Defined as the sum of all chemical reactions in the body.

  • Consists of two types:

    • Anabolic Processes: Involved in building up and storing energy (e.g., after meals).

    • Catabolic Processes: Involved in breaking down substrates for energy (e.g., during exercise).

Nutritional Components of Macronutrients

Proteins and Nitrogen

  • Unique because they contain nitrogen alongside carbon, hydrogen, and oxygen.

  • Nitrogen is part of amino groups, leading to the production of ammonia during metabolism, which is toxic.

  • Ammonia is converted to urea in the liver for excretion.

  • Kidneys play a critical role in processing proteins and nitrogen.

Practical Considerations

  • Overuse of protein supplements can lead to excess nitrogen conversion to urea, stressing kidneys.

  • Importance of hydration when consuming protein supplements.

Energy Contribution from Macronutrients

Resting Energy Sources

  • At rest, energy contribution is 50% from carbohydrates and 50% from fats.

Exercise Energy Sources

  • Highest fuel demand during exercise is carbohydrates.

  • Longer, less intense exercise utilizes fats as the energy source.

Thermic Effect of Food (TEF)

Definition

  • Energy expenditure associated with the digestion of macronutrients.

  • Affecting percentages per macronutrient:

    • Proteins: 15% - 30%

    • Carbohydrates: 5% - 10%

    • Fats: 0% - 3%

    • Indicates how much energy is needed to process each macronutrient.

Detailed Breakdown of Each Macronutrient

Carbohydrates

  • Sources: Potatoes, rice, bread, grains, pasta.

  • Provides approximately 4 kcal per gram.

  • Total storage capacity ~2,500 kcal (about 600 grams of glycogen primarily in muscle and liver).

  • Glycogen storage process is anabolic, whereas glycogen breakdown for energy is catabolic.

Fats

  • Easily available in various forms, primarily from nuts, dairy, and processed foods.

  • Yield approximately 9 kcal per gram, significantly higher than carbohydrates.

  • Body can store over 70,000 kcal of fats, demonstrating virtually unlimited storage capacity.

Proteins

  • Contribute 4 kcal per gram, primarily serve structural functions rather than energy.

  • Excess proteins can be converted into fats through lipogenesis.

Quiz Preparation

Important Concepts for Quizzes and Exams

  • Macronutrient roles:

    • Carbohydrates: Energy source during various physical activities.

    • Fats: Long-duration activities, energy reserve.

    • Proteins: Structural components, require careful management of intake.

  • Understanding storage capacities and metabolic pathways is critical for examinations.

  • Remember practical implications regarding nutrition particularly for athletes and those with kidney conditions.

Conclusion

  • Overview of metabolic functions and energy dynamics of nutrients.

  • Importance of hydration, balanced intake of macronutrients during training, and rest.

  • Reminder of practical implications of protein consumption, especially for workout routines.

Next Steps

  • Prepare for further detailed discussions in future classes, particularly on metabolic pathways.

  • Recap essential definitions and practical applications learned.

Questions and Engagement

  • Encourage the students to ask questions and clarify doubts regarding the material discussed.