although beginning stages of Aerobic Glycolysis make a small contribution.
Half Marathon
The Oxidative-aerobic system makes the greatest contribution to this event. The
Phosphagen and Glycolysis (anaerobic and aerobic glycolysis) energy systems will predominate
during the first one to two minutes of the race and in a sprint finish. What determines whether
the athlete is ‘burning’ carbohydrate, fat or protein during the run? Well, at rest, 70% of the
ATP produced is derived from fats, and 30% from carbohydrates. As the aerobic system begins
to predominate, fats turn over to carbohydrates (ultimate efficient fuel) and make the greatest
contribution to energy production at 100%6. Primarily fat will begin as the energy source, but as
exercise intensity is relatively low and constant, carbohydrates will last for a while. There will then
be a switch back to fat as the carbohydrate stores are depleted. Fat will be relied on more as
the duration of the race increases, until the duration reaches greater than 90 minutes. Here, the
fat and carbohydrate stores have been depleted in the muscles, so protein may be slightly used.
Carbohydrates are the most efficient source, but cannot always be relied upon. Again, the body
does not suddenly switch from one substrate to another – the cross over is a gradual shift.
Multi Sprint Sports
So far the examples have been straight forward. What about multi-sprint sports like
football, basketball, soccer, hockey and tennis? In short, all three energy systems make a
significant contribution. This athlete uses the phosphagen system to jump, throw and sprint, while
the anaerobic glycolysis system is taxed if the player has to make several back-to-back sprints.
And of course the aerobic glycolysis-oxidative-aerobic systems contribute for the entire duration
of the game, as the levels of duration increase.
Quick Summary
Phosphagen: 0 to 6 seconds, and is dominant from resting to near maximum intensity
Phosphagen and anaerobic glycosis: 6 to 30 seconds, dominant at near maximum intensity
Aerobic glycolysis: 30 seconds to 2 minutes, maximum intensity
Aerobic glycolysis and start of aerobic system: 2 to 3 minutes at moderate intensity
Aerobic system: over 3 minutes at light intensity
Manipulating the Energy Systems for Training Goals
The strength and conditioning professional’s ultimate goal is to manipulate the systems
to create the ultimate performance of the athlete for exercise, sport, or competition. The main
factors to specifically manipulate are, intensity, duration, rest, and sport specificity. The
systems, with examples of training variables focusing on specific training for the chosen energy
system, are as follows: