Kin 310 ExerciseWork Physiology Office hours K 8629

Kin 310 Exercise/Work Physiology • Office hours - K 8629 • Mondays and Wednesday 10 -11 am – or by appointment through email • class email list – announcements, questions and responses – inform me of a preferred email account • class notes will be posted on the web site in power point each week – can be printed up to six per page • lecture schedule along with reading assignment on web site • www. sfu. ca/~ryand/kin 310. htm 1

Energy Sources and Recovery from Exercise • Ch 2 Foss and Keteyian - Fox’s Physiological basis for Exercise and Sport- 6 th edition • all human activity centers around the capability to provide energy on a continuous basis – without energy cellular activity would cease - organism would die • Main sources of energy – biomolecules - carbohydrate and fat – protein small contribution • lecture will review metabolic processes with an emphasis on regulation and recovery 2

Energy • Energy - capacity or ability to perform work • Work - application of a force through a distance • Power - amount work performed over a specific time • forms of energy can be converted from one form to another – transformation of energy • chemical energy in food to mechanical energy of movement – Biological energy cycle 3

ATP - adenosine tri-phosphate • Energy liberated from food – used to manufacture ATP - Fig 2. 2 • only energy released from ATP can be utilized to perform cellular work – represents immediate source of energy available to muscle • bonds between phosphate groups – high energy bonds – broken by hydrolysis in presence of water • reaction reversible – phosphocreatine (PC) • and at points in metabolic pathways – oxidation reduction – oxidative phophorylation 4

Sources of ATP • Limited quantity of ATP available – constant turnover - requires energy • 3 processes - use coupled reactions • ATP-PC system (phosphagen) – energy for re-synthesis from PC • Anaerobic Glycolysis – ATP from partial degeneratoin of glucose – absence of oxygen – generates lactate • Aerobic System – requires oxygen – oxidation of carbohydrates, fatty acisds and protein – Krebs cycle and Electron Transport 5

Anaerobic sources • ATP -PC system – high energy phosphates • energy in PC bond is immediately available – – as ATP is broken down it is continuously reformed from ADP and PC enzyme - Creatine Kinase • also - ADP + ADP can form ATP – enzyme - myokinase • PC reformed during recovery when ATP formed through other pathways • Table 2. 1 - most rapidly available fuel source - very limited quantity 6

Anaerobic Glycolysis • Incomplete breakdown of glucose or glycogen to lactate • 12 separate, sequential chemical reactions – breakdown molecular bonds – couple reaction to synthesis of ATP – yields 2 (glucose) or 3 (glycogen) ATP • very rapid but limited production – lactate accumulates - fatigue • PFK - phosphofructokinase – rate limiting enzyme- slow step in reaction - further held back • Table 2. 2 7

Anaerobic Glycolysis • Lactate produced when low O 2 – pyruvate converted to lactate – enzyme LDH - lactate dehydrogenase Fig 2. 6 – frees up NAD+ required in glycolysis – continued rapid production of ATP • summary fig 2. 7 • glycogen vs. glucose 8

Aerobic Sources of ATP • Acetyl groups - 2 carbon units – formed from pyruvate and from Beta oxidation of free fatty acids • NAD and FAD - electron carriers – become reduced when molecules are oxidized forming NADH, FADH 2 – carry these hydrogen atoms to the electron transport chain – donated and passed down chain of carriers to form ATPs • oxygen is final acceptor of hydrogen's forming H 2 O • occurs in mitochonrial membrane system - cristae 9

Aerobic Glycolysis • • Sufficient oxygen Pyruvate diverted into mitochondia law of mass action 1 mole glycogen – 2 moles pyruvate – 3 moles ATP – 2 moles NADH (6 ATP) • Fig 2. 12 - Krebs Cycle • Key regulatory enzymes – PDH, CS, SDH • CO 2 produced as molecule breaks down and H are removed – oxidation - removal of electrons – reduction - addition of electrons 10

Krebs Cycle • Krebs - 2 GTP produced – 6 NADH and 2 FADH 2 • Electron Transport System – H passed down series of electron carriers by enzymatic reactions coupled to production of ATP – oxidative phosphorylation • each NADH - 3 ATP • each FADH 2 - 2 ATP – total 36 ATP from Krebs and ETS – glucose (38) glycogen (39) • for process to continue, must liberate NAD+ and FAD+ requires oxygen – high energy state= high ratio of NAD+/NADH 11

Fat Metabolism • Fat and Protein only oxidized in presence on oxygen • Fatty acids - 16 -18 carbon units – broken down into acyl groups • Beta oxidation Fig. 2. 15 – – – – uses 1 ATP produces 1 NADH and 1 FADH 2 same through Krebs as acetyl co-a 12 ATP total of 16 ATP for first acyl 17 for remainder last only 12 - does not go through beta oxidation • requires 15% more oxygen to produce a mole of ATP 12

Comparing the Energy Systems • Table 2. 5 • energy capacity - amount of ATP able to be produced independent of time • power - rate - in given amount of time • *aerobic - represents availability from glycogen only - fat unlimited • Rest • aerobic - supplies all ATP – mainly carbs and fats • some lactate ~10 mg/dl – does not accumulate, but LDH effective 13

Exercise • Both anaerobic and aerobic • relative roles depends on – intensity – state of training – diet of athlete • Two types of exercise investigated – near max - short duration – sub max - long duration • Fig 2. 18 glycogen depletion – activities below 60 % and above 90% little glycogen depletion – 75% significant depletion - exhaustion • 2. 18 b - rate of depletion dependant on demand – total depletion related to duration 14

Short duration • 2 -3 minutes high output exercise • fig 2. 19 - major energy source CH 2 O – ATP and PC will drop rapidly – restored in recovery • Aerobic limited by power output – also takes 2 -3 to increase • oxygen deficit - period during which level of O 2 consumption is below that necessary to supply all ATP required by exercise demands • ATP supplied by anaerobic systems – rapid accumulation of lactate – 200 mg/dl 15

Prolonged Exercise • 10 minutes or longer • fats and carbs • carbs dominate up to about 20 min – fats minor but supportive • after 1 hr fat dominant - also at lower intensities • fig. 2. 20 • fatigue not associated with lactate, other factors - discussed later in semester • Fig 2 -22 activites require blend of anaerobic and aerobic systems – energy continuum 16

Control and Regulation • Matching provision of energy to demand so performer does not experience early or undue fatigue • Enzymes, hormones, substrates interact to modify flow through pathways and reactions of each system • Fig 2. 7 factors – – – high vs low energy state of cell Hormone levels “amplification” of hormone effects modification of key enzymes power output requirements relative to aerobic power – adequacy of oxygen supply – competition for ADP 17

Regulation • Simply – regulation within muscle cell – influences from outside – both serve to modify regulatory enzymes • Fig 2. 23 • Energy State regulation – ADP/ATP ratio – very quick - tightly linked to rate of energy expenditure • Hormone Amplification – c. AMP 2 nd messenger systems amplification – Ep and Glucagon - activate phosphorylase - glycogen breakdown – lipase - fat breakdown 18

Regulation • Substrates – – – eg. NADH - buildup stimulates LDH - frees up NAD+ occurs when ETS is maximized can not oxidize NADH fast enough eg. Inc Pyruvate stimulates PDH - entry into Krebs • Oxidative State Regulation – – O 2 and ADP availability stimulates cytochrome oxidase final step in ETS low O 2 - inhibits CO - build up NADH, FADH 2 – key factor oxygen availability 19

Recovery from Exercise • Ch. 3 • process of recovery from exercise involves transition from catabolic to anabolic state – breakdown of glycogen to rebuilding of stores – breakdown of protein to protein synthesis for muscle growth • looking at all the processes that return the exerciser to resting state – – – oxygen consumption post exercise energy stores lactate oxygen stores intensity and activity specifics guidelines for recovery 20

Recovery Oxygen • Net amount of oxygen consumed during recovery from exercise • excess above rest in Litres • Fast and Slow components • first 2 -3 min of recovery - O 2 consumption declines very rapidly • then slowly to resting • Fig 3. 1 • Fast Component – – – restore myoglobin and blood oxygen energy cost of elevated ventilation energy cost of elevate heart activity replensihment of phosphagens volume = area under curve related to intensity not duration 21

Recovery Oxygen • Slow Component – elevated body temperature • Q 10 effect - inc metabolic activity – – – cost of ventilatoin and heart activity ion redistribution Na+/K+ pump glycogen re-synthesis effect of catecholamines oxidation of lactate • duration and intensity do not modify slow component until threshold of combined duration and intensity • 20 min and 80% 5 fold increase 22

Energy Stores • Both phosphagens and glycogen depleted during exercise • ATP/PC - fast component – measured by sterile biopsy, MRS • study of ATP production – 20 -25 mmol/L/min glycogen • rate of PC recovery indicative of net oxidative ATP synthesis • during exercise – PC down to 20%, ATP down to 70 % – PC lowest at fatigue, rises immediately with recovery • Fig 3. 2 - very rapid recovery – 30 sec 70%, 3 -5 min 100% 23

Phosphagen Recovery • Fig 3. 3 • occlusion of blood flow - no recovery • estimate 1. 5 L of oxygen for ATPPC recovery • Energetics of Recovery • Fig 3. 4 – breakdown carbs, fats some lactate – produce ATP which reforms PC – high degree of correlation between phosphagen depletion and volume of fast component oxygen • Fig. 3. 5 – power in athlete related to phosphagen potential - Wingate test 24

Glycogen Re-synthesis • Requires 1 -2 days and depends on – type of exercise – amount of dietary carbs consumed • Two types of exercise investigated – continuous endurance(low intensity) – intermittent exhaustive (high intensity) • Continuous • Fig 3. 6 - diet effect – minor recovery in 1 -2 hours, does not continue with fasting – complete resynthesis – requires high carb diet - 2 days – does not occur without carb diet – depletion related to fatigue – Fig 3. 7 - heavy training 25

Glycogen Re-synthesis • Intermittent, short duration exercise • Fig 3. 8 – significant re-synth in 30 min-2 hrs – did not require food – complete resynth did not require high carbs – only 24 hrs for 100 % recovery’ – rapid in first few hours • continuos vs intermittent – amount depleted – precursor availability • lactate, pyruvate, glucose – fiber type involved • re-synthesis faster in type II fibers 26

Lactate Reduction • Increasing intensity no change in lactate until threshold – large inc in [ lactate ] – influenced by duration and rest interval • Speed of lactate removal – fig 3. 10 - intermittent activity • Fig 3 -11 active vs passive – Active recovery - light activity – passive recovery - no activity • Fig 3 -12 intensity of recovery – untrained 30 -45% VO 2 Max – trained 50 -60% - some studies – glycogen re-synthesis slowed with high intensity active recovery 27

Lactate and the Slow Component of O 2 • fig. 3. 13 • Fig 3. 14 – close association between slow recovery component of O 2 and removal of lactate • restoration of O 2 stores – fast component - 10 -80 seconds • Ion concentrations – – – p. H - rapid return after light exercise heavy exercise dec. From 7 -6. 4 ~20 min for recovery close correlation to lactate and fatigue Max Contraction correlated with H+ and Pi (restored within 5 min) 28

Performance Recovery • Regain performance - force, power • med intensity 60 -80% – fast recovery - one minute • higher intensity bout – longer recovery • Aerobic fitness (high VO 2 max) important influence – good correlation between fast recovery of muscle function and VO 2 max • why? – Fast component requires O 2 • Guidelines Table 3. 2 29