Champaign, IL—A triathlete's physical ability may be an important factor, but when it comes to success in the sport, knowledge of the science of triathlon is equally critical. According to legendary endurance sport coach Joe Friel, knowledge of the science of triathlon is crucial to success in the sport. “A significant amount of energy is required to train for and compete in triathlon,” says Friel. “A practical knowledge of the physiology of energy production can help you design effective workouts and pace yourself more effectively during races.”
According to Friel, triathletes must first understand how their bodies process energy. “The basic unit of energy in the human body is adenosine triphosphate (ATP),” Friel says. “A simple way to think of a molecule of ATP is as an energy dollar bill. There are millions of molecules of ATP in the human body providing energy, and triathletes are constantly using and replenishing ATP, even when not exercising.” Friel notes that ATP utilization and production are similar to the daily scenario of spending money to pay bills and maintain a lifestyle.
In Triathlon Science (Human Kinetics, 2013), Friel explains how the body produces energy and offers practical knowledge of the three energy systems used by the body during exercise.
Immediate energy system
The technical name for the immediate energy system is adenosine triphosphate and is one of the two anaerobic energy systems. “The immediate energy system has the advantage of producing ATP very quickly but the disadvantage of producing a very limited supply of ATP,” says Friel. “In terms of athletic performance, the immediate energy system is the dominant energy system during very high-intensity, short-duration exercise lasting approximately 10 seconds or less.” Examples of the immediate energy system in athletic performance are the 100-meter sprint in track, 10-meter diving event, and weightlifting events.
Short-term energy system
The short term-energy system is also anaerobic and is known as glycolysis because the first of several biochemical reactions in this energy system involves the conversion of glycogen to free glucose. The short-term energy system has the advantage of producing more ATP than the immediate energy system but the disadvantage of taking longer to do so. “Another disadvantage is the short-term energy system produces lactic acid, which is quickly converted to lactate and positively charged hydrogen ions (H+),” Friel explains. “High concentrations of H+ create the acidic burning sensation in exercising skeletal muscle and, along with other biochemical, neural, and biomechanical factors, contributes to premature fatigue.” The short-term energy system is the dominant energy system used during high-intensity, moderate-duration exercise lasting approximately 30 to 120 seconds. Examples of the short-term energy system in athletic performance are the 400-meter sprint in track, 100-meter sprint in swimming, and 1,000-meter track cycling event.
Long-term energy system
The technical name for the long-term energy system is oxidative phosphorylation and is aerobic in nature, requiring oxygen to produce ATP. “The long-term energy system has the advantage of producing very large amounts of ATP compared with the other energy systems, but it has the disadvantage of taking more time to produce that relatively large amount of ATP,” Friel says. “The long-term energy system takes longer because it uses oxygen to produce ATP.” The long-term energy system is the dominant energy system in low- to moderate-intensity exercise lasting longer than 5 minutes. Examples of the long-term energy system in athletic performance are the marathon, 800-meter swim, and road cycling events. “The long-term energy system is the dominant energy system used during triathlon training and racing,” Friel says. “However, it is important to understand that it is not the only energy system used in triathlon.”
Although the dominant energy system used in triathlon is the long-term energy system, Friel stresses the importance of remembering the roles of the immediate and short-term energy systems in triathlon performance. “A triathlete should apply the scientific principles of the three energy systems to the design of daily workouts in order to consistently meet the specific goals of the training program,” Friel says. “Knowing when to train and how much time to devote to training each of the three energy systems is an important ingredient of success in triathlon and is reflective of a well-designed and scientifically based training plan.”
For more information, see Triathlon Science.