Source of energy for a running race athlete for the initial 3 minutes of running

Systems for energy during strenuous exercise or running 1. First System-Phosphagen system (8-10 seconds) - Immediate source of energy for Muscles is Creatine Phosphate. - But this is of limited supply in muscles, so depleted quickly 2. Second system -Anaerobic Glycolysis or Lactate system. (for 1-3 minutes ) - This system derives ATPs using Glucose derived from Muscle Glycogen 3.Third system -Aerobic System (or Mitochondrial Respiration) - can use carbohydrates, Fats, or Proteins to produce energy. - Slowest in providing energy, but more efficient than the other two systems - This system uses mainly TCA & ETC. Reasons for use of Phosphocreatine:- - Does not uses O2 - Does not produce lactate - Quickest source of energy - Most direct form of energy production