Aerobic Training

Aerobic Exercise PT 7428 Therapeutic Interventions

Objectives

  • Students will be able to:

    • Identify the differences among the metabolic energy systems utilized during exercise.

    • Classify activities by MET level or energy expenditure.

    • Describe acute and long-term physiological effects of exercise on the cardiovascular, respiratory, and metabolic systems.

    • Recognize age-related differences in cardiovascular, respiratory, and metabolic system parameters.

    • Distinguish between physical activity, exercise, and physical fitness.

    • Categorize physical activity guidelines based on age.

    • Identify the purposes of maximal or submaximal exercise testing.

    • Calculate maximum and target heart rates to stimulate a conditioning response in different populations.

    • Develop an aerobic exercise program for a patient based on a maximal or submaximal graded exercise test.

    • Perform maximal or submaximal exercise testing. (LAB)

Energy Systems and Energy Expenditure

Energy Systems Overview

  • Energy is stored as Adenosine Triphosphate (ATP) produced in muscles from blood glucose.

  • ATP is converted to Adenosine Diphosphate (ADP) and inorganic phosphate (P) to release energy for muscle cells.

ATP-PC System (Phosphagen System) - Immediate Energy

  • Involves:

    • Fuel Source: ATP and Phosphocreatine (PC) stored in muscle cell.

    • Type: Anaerobic system.

  • Characteristics:

    • Active for the first 10 seconds of high-intensity activity.

    • Quick replenishment when muscle is at rest.

    • Max capacity of the system is small, but max power is large.

  • Use case: Major energy source for up to 10 seconds during maximum effort activity.

Anaerobic Glycolytic System - Short-Term Energy

  • Involves:

    • Fuel Source: Glycogen (glucose) is rapidly converted to ATP via glycolysis in muscle cells.

    • Type: Anaerobic.

  • Characteristics:

    • Activated primarily during high-intensity activities within first 1-2 minutes of exercise.

    • Produces lactic acid as a by-product, which can lead to fatigue if accumulated.

    • Medium to high capacity and power.

Aerobic System - Long-Term Energy

  • Involves:

    • Fuel Source: Glycogen, fats, and proteins.

    • Type: Requires oxygen (aerobic).

  • Characteristics:

    • ATP is re-synthesized in mitochondria of muscle cells.

    • Utilizes slow-twitch fibers and fast-twitch IIA fibers.

    • Max capacity is large, but max power is small.

    • Predominantly used after approximately 2 minutes of exercise.

    • Puts less stress on the heart compared to anaerobic systems.

Summary of Energy Systems

  • ATP-PC System: Immediate, anaerobic, active for first 10 seconds.

  • Anaerobic Glycolytic System: Short-term, active for the first minute of high-intensity exercise.

  • Aerobic System: Long-term, predominates after the second minute of exercise.

Energy Expenditure

  • Energy expenditure is calculated based on the amount of oxygen consumed (VO2).

  • Kilocalorie (kcal):

    • The heat required to raise 1 kg of water by 1°C.

    • 5 kcal corresponds to 1 liter of O2 consumed.

  • Metabolic Equivalent (MET):

    • Used to express the energy cost of physical activity relative to resting metabolic rate (RMR).

    • 1 MET = 3.5 mL/kg/min (oxygen consumed per kg of weight per minute at rest).

    • There can be variance in MET levels based on factors such as sex, age, body size, and fat.

Classification of Activities by MET Usage

  • Light Work (1.6-2.9 METs):

    • Examples: Slow walking, desk work, light household chores, arts and crafts.

  • Moderate Work (3-5.9 METs):

    • Examples: Walking 3.0-4.0 mph, heavy cleaning, carrying wood, dancing, swimming, easy biking.

  • Vigorous Work (6+ METs):

    • Examples: Running, shoveling, heavy farming, competitive sports like basketball and soccer.

Physiological Response to Exercise

Acute Physiological Responses

  • Cardiovascular system adaptations to exercise:

    • Increased cardiac output (CO = HR x SV) driven by increased heart rate (HR), stroke volume (SV), and blood volume.

    • Increased venous return via working skeletal muscle and respiratory pumps, leading to vasoconstriction in non-working tissue.

    • Modulated by arterial baroreceptors controlling HR and muscle vasodilation.

Cardiovascular Responses to Exercise

  • Increased heart rate and stroke volume lead to:

    • Increased cardiac output and systolic blood pressure.

    • Oxygen utilization increases in working muscles, enhancing performance.

Respiratory Responses to Exercise

  • Enhanced gas exchange across alveolar-capillary membranes and increases in respiratory rate and tidal volume.

Chronic Physiological Changes from Aerobic Training

Cardiovascular Changes

  • At Rest: Decreased resting HR and BP, increased blood volume, possible cardiac hypertrophy.

  • During Exercise: Decreased HR relative to intensity, faster recovery times, and increased stroke volume leading to higher cardiac output.

Metabolic Changes

  • Potential reductions in muscle glycogen depletion rates and lower lactate levels during submaximal exertion, enhancing endurance.

Other System Changes

  • Decreases in body fat and blood lipid levels, along with improvements in bone density and heat acclimatization.

Definitions and Guidelines

Physical Activity vs. Exercise

  • Physical Activity: Bodily movement producing energy expenditure above resting levels; includes occupational, recreational, and household activities.

  • Exercise: Planned, structured, and repetitive movements aimed at physical fitness improvement.

Physical Fitness

  • Integrated measure of cardiorespiratory, musculoskeletal, and psychological function enabling efficient performance of activities. It encompasses muscle strength, endurance, flexibility, and balance.

Physical Activity Guidelines

Children (6-17 Years)

  • 60 minutes/day of moderate to vigorous physical activity, including muscle and bone-strengthening activities at least 3 days/week.

Adults (18-64 Years)

  • 150-300 minutes of moderate or 75-150 minutes of vigorous intensity activity weekly, spread throughout the week, with muscle strengthening at least 2 days/week.

Older Adults (65+) and Adults with Chronic Health Conditions

  • Same guidelines as adults aged 18-64, with additional balance exercises at least 2 days/week.

Exercise Testing and Prescription

VO2max

  • Definition: Maximum oxygen consumption indicating the body's capacity to use oxygen.

  • Influenced by oxygen transport, oxygen-binding capacity of blood, cardiac function, and muscular oxidative potential.

Indications for Exercise Testing

  • To predict cardiovascular events, assess medical intervention responses, and prescribe exercise.

Contraindications for Exercise Testing

  • Absolute: Severe medical conditions such as aortic stenosis, acute MI, unstable angina, and pulmonary embolism.

  • Relative: High blood pressure, arrhythmias, and recent CVA.

Maximum Heart Rate Calculation

  • Formula: 220 - age for traditional estimates; 208 - (0.7 x age) for a more accurate approach in healthy adults.

Target Heart Rate Calculation

  • Simple formula: THR = %intensity(HRmax).

  • Heart Rate Reserve (HRR) method: THR = HRrest + %intensity(HRmax - HRrest).

Summary of Exercise Prescription

  • Follow the FITT Principle: Frequency, Intensity, Time, Type.

  • Calculate target heart rates and ensure exercise intensity is sufficient for conditioning without being overly fatiguing. Recognize that physical activity doesn't need to be exhaustive for cardiovascular conditioning to be achieved.