Energy Production
• conversion of chemical energy to mechanical energy stored
in the form of ATP
• breakdown of ATP releases energy and produces heat
– used by muscle
• sliding of myosin and actin
– transport of molecules
• glucose, Ca++ and other ions across cell membranes
• for repair
• conduction of nervous system
• rest
– ATP synthesis and breakdown remain steady
• stored ATP only lasts a few seconds during contraction
• maximal exercise
– ATP breakdown is 200 times faster than rest
• insufficient ATP to meet demand causes fatigue
Protein
• very little used for energy (<5%)
• proteins > AA
• some AA to glucose (gluconeogenesis), pyruvic acid or
acetyl CoA
– used in oxidative process
• nitrogen forms other AA
– excess to urea
• uses energy
CHO (C6H12O6)
• faster energy - short duration
– stored as liver glycogen and muscle glycogen
– blood glucose immediate energy
• 38 ATP (70% of energy for ATP, 30% lost as heat )
– muscle glycogen depleted 20-30% with short, highintensity bout of exercise
• depletion rate of 18.8 umol/g per minute
• ? glycogen availability causes fatigue
– moderate intensity exercise of 56 minutes
• depletion rate of 1.1 umol/g per minute
• prolonged exercise results in greatest depletion of
muscle glycogen
– glycogen concentration fell 50-60%
Fats
• triglycerides, phospholipids and cholesterol
• triglycerides
– used for energy (69% for energy, 31% lost as heat)
– stored in muscle and adipose tissue
– 1 glycerol and 3 FFA (lypolisis)
– FFA in blood enter fibers by diffusion
• rate of entry regulated by it’s own concentration
gradient
• increased FFA in blood drives FFA into muscle
Metabolic Pathways
• aerobic (oxidative phosphorylation)
• anaerobic alactic (ATP-PCr)
• anaerobic lactic (anaerobic glycolytic)
• all active at all times
– % contribution varies with exercise intensity and
duration
– anaerobic used for high intensity, short duration
exercise
– aerobic used for low to moderate, longer duration
exercise
• condition to most important pathway
– “sport specific”
ATP-PCr
• start-up system
• simplest pathway, readily available energy
• phosphocreatine (PCr) rebuilds ATP
– not used for direct cellular work
• creatine kinase releases Pi from PCr, binds to ADP
• O2 not needed
• sprint for 10 - 20 sec, majority of energy from PCr
– > 20 sec, very little contribution to energy supply
• rapid depletion of PCr and ATP
• no toxic waste product
• replenish supply of PCr in 3 min at rest
• barrels, roping, ect.
Anaerobic Glycolytic
• ATP produced from breakdown of glucose via special
enzymes; lactate dehydrogenase (LDH)
• no O2 needed
• lactate produced
• duration of energy supply 20-120 sec
• glucose - 99% of all sugars in blood
– digestion of CHO
– breakdown of liver glycogen
• glycogen  glucose-1-phosphate (glycogenolysis)
• breakdown of G-6-P to pyruvate (glycolysis)
Glycolysis
• early use with high intensity exercise
– ATP-PCr system
• does not produce large amounts of ATP
• glycogen (anaerobic pathway)
– 3 ATP + 2 NADH = 9 ATP
• glucose (anaerobic pathway)
– 2 ATP + 2 NADH = 8 ATP
• glycogen produces pyruvate, O2 determines fate of
pyruvate
– O2 to Kreb’s cycle
– no O2, lactic acid
Oxidative Pathway
• most complex pathway
• disassembles fuels with O2
• O2 production of ATP in mitochondria
– next to myofibrils and in sarcoplasm
• high energy yield
• slow production of energy
– oxidative production of ATP requires 3 processes
• glycolysis
• Kreb’s cycle
• electron transport chain
• glycolysis  pyruvate
– pyruvate + O2  acetyl CoA
• Kreb’s cycle (per pyruvate:1/2 glucose)
– complete oxidation of acetyl CoA
– 2 ATP + 1 FADH2 + 3 NADH
– C + O2  CO2 expired
• electron transport chain
– glycolysis produces H+ (too acidic)
• FADH2 and NADH transport H+ to electron
transport chain
• H+ split into protons and electrons
• phosphorylation produces ATP
• H+ + O2  H2O expelled
Energy Stores
Fuel
kcal
ATP
9
Creatine phosphate
45
Glycogen
17,988
Fat
152,889
Lactic Acid
• lactate
– lactic acid combined with Na+ or K+ to form salt
• regulated by feedback system
– accumulation of lactate in muscle inhibits further
glycogen breakdown
• acidity decreases pH of muscle and Cal-binding
capacity
• slows reactions for energy production resulting in
fatigue
• lactate concentration in muscle
– production level
– rate of removed from muscle by blood
• detoxified in liver
– amount used as energy by aerobic metabolism
• recovery at rest - 3 hours
• light exercise aids in removal of lactate
• additional increase in blood lactate concentration at end of
work bout
– > 5 min
• removal rate exceeds release from muscle
– decreased blood lactate concentration
• measure of fitness
– decrease level of lactate following conditioning for
same work load