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M04.05.10 Regulation of Smooth Muscle
Exercise physiology is the study of the acute responses and chronic adaptations of the human body to physical activity. This field explores how different systems of the body respond to exercise, including the cardiovascular, respiratory, muscular, and metabolic systems. Understanding these physiological responses is crucial for developing effective training programs, preventing injuries, and improving athletic performance.
Overview of Exercise Physiology
Key Concepts:
- Homeostasis: The body’s ability to maintain a stable internal environment during exercise.
- Adaptation: Long-term physiological changes resulting from regular exercise.
Cardiovascular Responses to Exercise
Acute Responses:
- Heart Rate (HR): Increases linearly with exercise intensity.
- Stroke Volume (SV): Increases with moderate exercise, then plateaus.
- Cardiac Output (CO): Increases to meet the oxygen demands of muscles.
- Blood Flow Redistribution: Blood flow is redirected from non-essential organs to active muscles.
| Parameter | Rest | Moderate Exercise | Intense Exercise |
|---|---|---|---|
| Heart Rate (bpm) | 60-80 | 120-140 | 160-200 |
| Stroke Volume (mL) | 70-90 | 100-130 | 110-140 |
| Cardiac Output (L/min) | 5-6 | 10-14 | 20-25 |
Chronic Adaptations:
- Increased SV and CO: Due to heart muscle hypertrophy.
- Lower Resting HR: Improved efficiency and endurance.
- Enhanced Capillarization: Better oxygen delivery and waste removal.
Respiratory Responses to Exercise
Acute Responses:
- Ventilation Rate: Increases to match the metabolic demands.
- Tidal Volume (TV): The amount of air per breath increases.
- Alveolar Ventilation: Enhances gas exchange efficiency.
| Parameter | Rest | Exercise |
|---|---|---|
| Ventilation Rate (breaths/min) | 12-20 | 35-45 |
| Tidal Volume (mL) | 500 | 1500-2000 |
| Alveolar Ventilation (L/min) | 4-5 | 60-100 |
Chronic Adaptations:
- Increased Lung Capacity: Enhanced oxygen intake and CO2 removal.
- Improved Ventilatory Efficiency: Lower breathing rates at submaximal workloads.
Muscular Responses to Exercise
Acute Responses:
- Increased Blood Flow: To supply active muscles with oxygen and nutrients.
- Enhanced Glycogenolysis: Breakdown of glycogen for energy.
| Parameter | Rest | Exercise |
|---|---|---|
| Muscle Blood Flow (% of CO) | 20 | 80-85 |
| Muscle Glycogen Utilization | Low | High |
Chronic Adaptations:
- Muscle Hypertrophy: Increase in muscle size and strength.
- Enhanced Mitochondrial Density: Improved aerobic capacity and endurance.
- Increased Myoglobin Content: Better oxygen storage and transport within muscles.
Metabolic Responses to Exercise
Acute Responses:
- Increased ATP Production: Through aerobic and anaerobic pathways.
- Elevated Lactate Levels: During high-intensity exercise.
| Parameter | Rest | Exercise |
|---|---|---|
| ATP Production Rate | Low | High |
| Blood Lactate (mmol/L) | <1 | 4-20 |
Chronic Adaptations:
- Improved Insulin Sensitivity: Enhanced glucose uptake and utilization.
- Increased Aerobic Enzymes: Better energy production efficiency.
Side Notes
Key Points to Memorize:
- VO2 Max: Maximum oxygen uptake, a key indicator of cardiovascular fitness.
- Lactate Threshold: The exercise intensity at which lactate begins to accumulate in the blood.
- EPOC (Excess Post-exercise Oxygen Consumption): The increased rate of oxygen intake following strenuous activity.
Bibliography
- Powers, S. K., & Howley, E. T. (2017). Exercise Physiology: Theory and Application to Fitness and Performance. McGraw-Hill Education.
- Wilmore, J. H., Costill, D. L., & Kenney, W. L. (2012). Physiology of Sport and Exercise. Human Kinetics.
- McArdle, W. D., Katch, F. I., & Katch, V. L. (2015). Exercise Physiology: Nutrition, Energy, and Human Performance. Lippincott Williams & Wilkins.
- Brooks, G. A., Fahey, T. D., & Baldwin, K. M. (2004). Exercise Physiology: Human Bioenergetics and Its Applications. McGraw-Hill Education.