energy systems

Michael Phelps and Competitive Swimming 

Competitive swimming calls for athletes to use all three energy systems and the amount of energy that each system contributes to the athlete depends on the distance and intensity of the race. For example Michael Phelps competed in events that reneged from the 100-meter butterfly to the 400-meter individual medley. This means that his body would have relied on a combination of many energy systems and this included the ATP-PC system, the anaerobic glycolytic system as well as the aerobic system. 

ATP-PC System 

The ATP-PC system or the Anaerobic Lactic System helps the body to provide immediate energy for explosive movements. This is the dominant energy system at the start of a race and is also prominent during dives off the block, powerful underwater kicks and turns.

Duration: 10-15 seconds

Fuel Source: Stored ATP and phosphocreatine in the muscles. 

Example: At the start of a 100-meter butterfly race Phelps body relies heavily on stored ATP and phosphocreatine to help him generate the speed and power that is required to perform at such a high level.

Advantages:

• Supports explosive movements
• Provides the athletes with energy very quickly 

Limitations:

• The energy supply given only lasts a few seconds before it becomes depleted 
  

Anaerobic Glycolytic System (Glycolysis) 

When the ATP-PC stores become depleted then the anaerobic glycolytic system becomes the dominant and primary source of energy. This system is known also as the lactic acid system and breaks down carbohydrates without oxygen and provides the body with energy for high-intensity swimming events. 

Duration: 15 seconds to 3 minutes 

Fuel Source: Glucose (glycogen stored in the muscles) 

Example: Phelps relies heavily on the anaerobic glycolytic system to maintain his speed during a 100-meter or 200-meter butterfly race. The production of lactic acid in the muscles contributes to the muscle fatigue that swimmers experience towards the end of a race. 

Advantages:

• Supports high-intensity efforts 
• Produces energy fast

Limitations: 

• Accumulation of lactic acid causes fatigue 
• Does not sustain activity for long periods of time 
  

Aerobic System (Oxidative System) 

This system is crucial during longer events and during training. The aerobic system or cellular respiration provides a continuous supply of energy and helps the athlete's body recover between intense efforts. 

Duration: 120 seconds and beyond

Fuel Source: Glycogen, Fats and Proteins 

Example: One of Phelps’ signature events the 400-meter individual medley requires the aerobic system to contribute significantly throughout the race. This system plays a major role during his longer training sessions where he is known to have swam thousands of meters per day. 

Advantages:

• Provides large amounts of energy
• Assists in recovery
• Helps to support prolonged activity

Limitations:

• Provides energy more slowly compared to the other systems. 
  

Michael Phelps Success

Why was Michael Phelps so successful? Phelps trained all three of these energy systems vigorously and extensively. His race starts relied on the ATP-PC system for explosive power, his continued ability to maintain speed relied on the anaerobic glycolytic system and his endurance throughout a race was supported by cellular respiration, his highly developed aerobic system. His balanced development of each system allowed him to excel in both sprint and middle-distance swimming events. 

Energy System Contributions During a Race 

100-Meter Butterfly (Approx. 50 Seconds) 

400-Meter Individual Medley (Approx. 4 Minutes)