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, high-intensity 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