Energy Systems in Human Physiology

Energy is essential for physical movement, maintaining body temperature, and metabolic activities.
Adenosine Triphosphate (ATP) is the primary energy source for muscle movement, particularly stored in muscles for quick access.
ATP is limited in storage, requiring additional systems for sustained energy production.
Three ATP production systems: ATP-CP, Glycolytic (Lactic), and Oxidative (Aerobic).
ATP-CP and Glycolytic systems function anaerobically, while the Oxidative system operates aerobically.

Operates during high-intensity movements lasting 5-15 seconds, such as jumping or throwing.
Utilizes stored ATP in muscles and creatine phosphate (CP) to provide brief energy bursts.
Both ATP and CP are finite, limiting endurance for prolonged activities.

Relies on the quick breakdown of carbohydrates to generate ATP.
Glucose circulates in the bloodstream, while glycogen is stored in muscle and liver.
ATP production occurs through glycolysis, yielding lactate and hydrogen ions.
Accumulation of hydrogen ions can lead to muscle acidity, contributing to fatigue and sensations of burning.
Efficient for quick energy over 1-2 minutes, such as sprints; not sustainable for longer durations.

Utilizes oxygen through the Krebs cycle and electron transport chain for ATP production.
Slower ATP production compared to anaerobic systems, but supports sustained energy output.
Capable of utilizing carbohydrates and fats for fuel; proteins may be used when necessary.
Ideal for extended activities, such as marathon running, due to prolonged energy availability.

Increased heart rate reflects heightened demand for oxygen and nutrients during physical activity.
Resting heart rate (RHR) averages between 60-80 beats per minute (BPM).
Heart rate increases through five distinct zones, each with specific responses and benefits.

Zone 1 (50-60% HR Max):
- Duration: 20-40 minutes
- Purpose: Warm up/Recovery
- Benefits: Aids recovery and prepares for higher intensity workouts.
Zone 2 (60-70% HR Max):
- Duration: 40-80 minutes
- Purpose: Base fitness level
- Benefits: Burns fat for energy, supports weight loss, improves endurance.
Zone 3 (70-80% HR Max):
- Duration: 10-40 minutes
- Purpose: Aerobic capacity
- Benefits: Enhances aerobic fitness, improves blood circulation efficiency, balances energy from carbohydrates and fats.
Zone 4 (80-90% HR Max):
- Duration: 2-10 minutes
- Purpose: Anaerobic capacity
- Benefits: Maximizes calorie burn, improves overall performance, increases lactate and aerobic thresholds.
Zone 5 (90-100% HR Max):
- Duration: Less than 5 minutes
- Purpose: Maximum capacity
- Benefits: Represents peak effort in exercise; sustainable only for short bursts.