Chapter 2 Fuel Sources & Exercise Metabolism

Table3.7 Major characteristics of the human energy systems ATP-PCr Lactic Acid Oxygen Main energy source ATP, PCr CHO Fat Intensity level Highest High Lower Lowest Rate of ATP Production Power ATP Capacity Low Endurance Capacity O2 Needed No Yes Track Event 100 m 200-800 m 5,000 m Ultra Time 1-10 s 30-120 s >5 min hours

Table 3.8 Percentage contribution of anaerobic and aerobic energy sources during different time periods of maximal work Time 10 sec 1 min 2 4 10 min 30 min 50 min 130 min Anaerobic Aerobic 85 15 70 30 50 5 90 98 99

Energy Stores In the Average Man Mass (lb) Energy (kJ) Energy (kcal) Rx Time (Min) Liver Glycogen 0.22 1,600 400 20 Muscle Glycogen 0.88 6,400 80 Blood Glucose 0.022 160 40 2 Fat 23 390,000 93,000 4,900 Protein 18.75 142,000 34,000 1,800

Some Possible Causes of Fatigue During Exercise Increased formation of depressant neurotransmitters Increased serotonin levels Decreased levels of energy substrates Phosphocreatine Muscle glycogen Blood-sugar level Branched-chain amino acids

Fatigue Sites Cont’d Disturbed intracellular environment Impaired calcium recycling Disturbed acid-base balance Increased H+ due to lactic acid Decreased oxygen transport Decreased blood volume due to dehydration Increased core temperature Decreased cooling due to dehydration Disturbed electrolyte balance Increased or decreased concentration due to sweat losses and H2O replacement