Aerobic and Anaerobic Systems in Triathlons

Triathlons involve both the aerobic and anaerobic systems.  Training for a triathlon requires training for quick starts, long stages at consistent paces, and sprints to the finish.   Endurance and speed are aerobic and require oxygen for the energy systems.  Bursts of power and speed are anaerobic and do not require oxygen to utilize stored energies.

The aerobic system completely breaks down carbohydrates, fats, and proteins through the citric acid cycle and the electron transport chain.  This produces up to fifteen times as much ATP as the anaerobic system and is a sustainable source of energy (Insel et al, 2010).  Whether it is a super-sprint, sprint, traditional, or Iron Man, a triathlon requires the athlete to test her endurance.

The aerobic system gives the athlete the energy needed to complete all three legs of the race.  When oxygen is available, a pyruvate molecule is converted to an acetyl CoA molecule.  This is a one-way process.  When moving to the anaerobic from the aerobic system, as in a sprint to the finish, pyruvate forms lactate, which is an alternative fuel.  This lactate can be reconverted back to pyruvate when it is no longer needed (Insel et al, 2010).

The anaerobic system only breaks down carbohydrates through glycolysis.  These readily available energies are used for short bursts of speed at the start of each leg.  The anaerobic system again kicks in when the triathlete needs power and speed to sprint to the end or to pass another racer within a leg.

The transitions between legs are generally aerobic; however, there are instances of anaerobic power.  Transitions need to be quick and efficient.  The act of jogging to the transition spot is aerobic, but the sprint to the next leg, or any leaping and jumping over obstacles, is anaerobic.

As can be seen, a triathlon utilizes both the aerobic and anaerobic systems.  There are several instances where the athlete needs sudden bursts of power and speed in order to move ahead of the pack.  These bursts are sporadic and interspersed in the endurance phases of each leg.  During the event, there is more time spent in the aerobic system, but the anaerobic system is crucial to moving ahead of the pack.

Reference:
Insel, Paul; Turner, R. Elaine; Ross, Don (2010)  Discovering Nutrition, Third Edition  Jones and Bartlett