Foundations of Exercise Science

1. Describe the main macronutrients that provide energy for the body

2. Explain how energy content (caloric value) is quantified.

3. Describe the techniques used to quantify human body composition.

4. Compare and contrast the objectivity and validity of various body composition assessment techniques.

5. Explain the importance of body composition and/or dimensions in sport, health and disease.

Macronutrients Providing Energy for the Body

• Carbohydrates: The primary source of energy for the body, especially for brain function and high-intensity exercise. They are broken down into glucose, which can be used immediately for energy or stored in the liver and muscles as glycogen for later use.

• Proteins: Composed of amino acids, proteins are essential for muscle repair and growth. While primarily used for structural purposes, they can also serve as an energy source when carbohydrates are scarce, providing 4 calories per gram.

• Fats: Fats provide the most concentrated source of energy, yielding 9 calories per gram. They are crucial for the absorption of fat-soluble vitamins (A, D, E, K) and support cell membrane integrity. Fats can be classified into saturated, unsaturated, and trans fats, with unsaturated fats being the healthiest option.

Energy Content (Caloric Value) Measurement

• The energy content of macronutrients is quantified in kilocalories (commonly referred to as calories). This is determined through a process called calorimetry, which measures the amount of heat produced when food is combusted. The caloric values for macronutrients are:

  • Carbohydrates: 4 kcal/g

  • Proteins: 4 kcal/g

  • Fats: 9 kcal/g

Techniques to Quantify Human Body Composition

• Dual-Energy X-ray Absorptiometry (DEXA): A non-invasive imaging technique that provides a detailed assessment of body fat, lean mass, and bone density.

• Bioelectrical Impedance Analysis (BIA): A method that estimates body composition by sending a low-level electrical current through the body and measuring resistance to the flow.

• Hydrostatic Weighing: This technique involves measuring body density by comparing a person's weight in water versus their weight on land, allowing for a calculation of body fat percentage.

• Skinfold Measurements: Using calipers to measure the thickness of skinfolds at various body sites to estimate total body fat percentage based on standardized equations.

Objectivity and Validity of Body Composition Assessment Techniques

• Objectivity: Techniques such as DEXA and hydrostatic weighing offer high objectivity due to their reliance on standardized equipment and methodologies. In contrast, skinfold measurements may be subject to user error and variability.

• Validity: Some methods may provide valid estimates of body composition for general population groups but may not be as accurate for athletes or individuals with atypical body fat distributions. DEXA is often regarded as one of the most valid methods for clinical assessments.

Importance of Body Composition in Sport, Health, and Disease

• In sports, optimal body composition is crucial for performance and injury prevention, as it can affect strength, agility, and endurance.

• In health, a balanced body composition contributes to overall wellness and reduces the risk of chronic diseases, such as obesity, diabetes, and cardiovascular disease. Body composition assessments can guide tailored nutritional and exercise programs.

• In disease management, monitoring changes in body composition can provide insights into treatment efficacy, recovery, and overall prognosis, particularly in conditions like cancer or heart disease, where muscle wasting may occur.