Chapter 2 Fuel Sources & Exercise Metabolism

Table3.7 Major characteristics of the human energy systems ATP-PCrLactic Acid Oxygen Main energy sourceATP, PCrCHO Fat Intensity levelHighestHighLowerLowest Rate of ATP Production HighestHighLowerLowest PowerHighestHighLowerLowest ATP CapacityLowestLowHighHighest Endurance CapacityLowestLowHighHighest O 2 NeededNo Yes Track Event100 m m5,000 mUltra Time1-10 s s>5 minhours

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

Energy Stores In the Average Man Mass (lb) Energy (kJ) Energy (kcal) Rx Time (Min) Liver Glycogen 0.221, Muscle Glycogen 0.886,4001,60080 Blood Glucose Fat23390,00093,0004,900 Protein ,00034,0001,800

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 H 2 O replacement