There are 3 energy systems that runners have to be aware of and each system has to be trained a specific way.

The 3 energy systems:

ATP – PC (Adenosine Triphosphate Phosphocreatine) or referred to as the Power system (phosphagen)  (non-oxygen dependent) (without oxygen) . Running events lasting 10-30 sec.

Glycolytic system (anaerobic) (non-oxygen dependent) (without oxygen) (dependent on muscle glycogen) (stored carbohydrates). Running events lasting  1-2 min.

Aerobic or Oxidative  system (oxygen dependent) (with oxygen). Running events lasting several minutes to hours.