UNIT_2

UNIT_2 - Exercise Metabolism - The study of how the body...

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Exercise Metabolism -- The study of how the body provides the energy necessary to generate the desired power output. Fatigue = The inability to maintain a desired power output. ATP = source of energy in the body (i.e. ATP hydrolysis liberates energy) 4 major sites of ATP hydrolysis during muscular work : 1. Cross-bridge cycle (a.k.a. actomyosin interaction) 2. SR Ca++ pumps 3. Sarcolemma Na+/K+ pumps 4. Neuronal membrane Na+/K+ pumps
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DOES ATP DEPLETION CAUSE FATIGUE? Cost of walking = ~6 kcal/min 6 kcal/min x 15 min = 90 kcal ATP contains 10 kcal / mole 90 kcal÷10 kcal / mole=9 moles of ATP needed to walk 15 minutes 1 mole of ATP = 500 g 9 moles x 500 g = 4500 g of ATP needed to walk 15 minutes 0.005 moles of ATP per kg of muscle (due to cell volume limitations) 9 ÷ 0.005 = 1800 kg (~4000 lbs or 2 tons) of muscle to walk 15 minutes SINCE ATP CANNOT CROSS CELL MEMBRANES FROM WHERE DOES THE 9 MOLES OF ATP COME? FATIGUE IS NOT RELATED TO ATP DEPLETION BUT INSTEAD IT IS RELATED TO THE RATE OF ATP RESYNTHESIS !!! IN OTHER WORDS FATIGUE OCCURS WHEN THE RATE OF ATP RESYNTHESIS IS LESS THAN THE RATE OF ATP USAGE (or BREAKDOWN or HYDROLYSIS)
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1. The body has three different systems to maintain ATP balance. (maintaining ATP balance a.k.a. ATP buffering) 2. These systems differ in their rate of ATP resynthesis. 3. Therefore, the primary cause of fatigue is the inability to match the rate of ATP resynthesis with the rate of ATP hydrolysis. (i.e. when you fatigue, power output slows down until it can match an ATP resynthesis rate.)
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System Max Power (kcal/min) Max Capacity (stored kcal) Immediate 36 11 Glycolysis 16 15 Oxidative 10 480 Maximal Power and Capacity of the Three Energy Systems
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Immediate & Glycolysis Oxidative 0 10 20 30 40 50 60 70 80 90 100 %Aerobic I---------I--------I--------I-------I--------I--------I--------I--------I--------I---------I %Anaerobic 100 90 80 70 60 50 40 30 20 10 0 I I I I I I I I I Distance (m) 100 200 400 800 1.5k 3.2k 5k 10k Marathon Time (min:sec) 0:10 0:20 0:45 1:45 3:45 9:00 14:00 29:00 135:00 REMEMBER! 1. All 3 metabolic systems (pathways) are operating at all times. 2. The rate of a particular system and its relative contribution varies with the work demand.
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IMMEDIATE OR "BORROWING" ENERGY SYSTEMS Consists of two parts : 1. ATP-CP or Phosphagen System This reaction uses the enzyme creatine phosphokinase or CPK (aka Creatine Kinase or CK) CPK ADP + CP =========> ATP + C 2. Myokinase System This reaction uses the enzyme myokinase (a.k.a. adenylate kinase). myokinase ADP + ADP ===========> ATP + AMP
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NOTE: A build up of AMP can force the reaction to work backwards, so you end up producing ADP not ATP. myokinase ATP + AMP ===========> ADP + ADP Therefore the muscle cells must do one of the following to keep [AMP] low. 1. FAST MYOSIN containing muscle cells
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This note was uploaded on 11/18/2009 for the course KIN 3515 taught by Professor Nelson during the Fall '09 term at LSU.

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UNIT_2 - Exercise Metabolism - The study of how the body...

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