<prompt> Source of energy for a running race athlete for the initial 3 minutes of runningFree fatty acidCreatine phosphateMuscle glycogenBlood Glucose  <response>: 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 