1 / 27

Kin 310 Exercise/Work Physiology

Kin 310 Exercise/Work Physiology. Office hours - K8621 W 10:30-12:20 or by appointment (ryand@sfu.ca) 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

blindo
Download Presentation

Kin 310 Exercise/Work Physiology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Kin 310Exercise/Work Physiology • Office hours - K8621 • W 10:30-12:20 • or by appointment (ryand@sfu.ca) • 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/kin310.htm

  2. Overview • Discussion of the physiological basis of exercise and work • Cellular bioenergetics • Providing ATP to meet demand • Cardiovascular and respiratory compensations and capacities • Limitations and adaptations to training • Molecular level adaptation • activity changes the cellular environment - stimulating adaptation to better meet demand • Fatigue - inability to sustain activity level • description of fatigue in the CNS, the neuromuscular junction and the muscle cell • Ageing - change in physiological capacities - impacts of disease and activity level • Assessment of work load and physical capacity for exercise and work • Exercise and the Environment • Heat and barometric pressure can create additional demands on physiological systems

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

  4. Energy • Energy - capacity or ability to perform work • Work - application of a force through a distance • Biological work - transport, mechanical and chemical work • Power - amount work performed over a specific time (rate of work) • Transformation of energy - forms of energy can be converted from one form to another • chemical energy in food is transformed into mechanical energy of movement or other biological work • Biological energy cycle

  5. ATP - adenosine tri-phosphate • Energy harnessed from molecular bonds in biomolecules - • used to resynthesize ATP - Fig 2.2 • only energy released from ATP can be utilized to perform cellular work • ATP in solution represents immediate source of energy available to muscle • enzyme (eg. ATPase) break high energy bonds between phosphate groups • Forming ADP + Pi + energy • Energy used to do biological work • Eg Calcium ATPase, myosin ATPase • Reaction is reversible (reform ATP) • CP -creatine phosphate (phosphocreatine) • Enzyme CK - Creatine Kinase • Kinases (eg glycolysis) • oxidative phosphorylation • form NADH, FADH2 then form ATP

  6. Sources of ATP • Limited quantity of ATP available • constant turnover (re-synthesis) - requires energy • 3 processes - use coupled reactions • ATP-PC system (phosphagen) • energy for re-synthesis from CP • Anaerobic Glycolysis • ATP from partial breakdown of glucose • Limited quantities of glucose • absence of oxygen • generates lactate as end product (*pH) • Aerobic System • requires oxygen • oxidation of carbohydrates, fatty acids and protein • Krebs cycle and Electron Transport

  7. Anaerobic sources • ATP -PC system (fig 2.4) • high energy phosphates • energy in CP bond is immediately available • as ATP is broken down it is continuously reformed • ADP + PC(Creatine Kinase) -> ATP • ADP + ADP (myokinase) -> ATP • CP reformed during recovery • from ATP formed through aerobic pathways • Table 2.1 - most rapidly available fuel source - very limited quantity • Depleted with 10 seconds of maximum activity • Recovers quickly

  8. 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 • Rapid but limited production • Limited glycogen stores • lactate accumulates -> acidity -> fatigue - unable to sustain demand • PFK - phosphofructokinase • rate limiting enzyme- slow step in reaction - inhibited by acidity • Table 2.2

  9. Anaerobic Glycolysis • Pyruvate is final product of glycolysis • pyruvate is converted to lactate when aerobic ATP production can not meet demand for ATP utilization • Inadequate O2 delivery (or high demand) • enzyme LDH - lactate dehydrogenase • Redox reaction (Fig 2.6) • *frees up NAD+ required in glycolysis • Allows rapid production of ATP through glycolysis - until acidity shuts it down • summary fig 2.7 • glycogen - endogenous fuel • within muscle • glucose - exogenous fuel • comes from blood glucose, released from liver glycogen

  10. 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 biomolecules are oxidized - form NADH, FADH2 • carry these hydrogen atoms to the electron transport chain • donated and passed down chain of carriers to form ATP • Oxidative - phosphorylation • oxygen is final acceptor of hydrogen, it is reduced to H2O • occurs in mitochondrial membrane system - cristae

  11. Krebs Cycle • Fig 2.12 - Krebs Cycle (Citric Acid cycle) • Key regulatory enzymes • ICDH(Iso citrate De-hydrogenase), CS (citrate synthase), KGDH (alpha ketoglutarate DH) • NADH - inhibits enzyme activity • High NADH - indicates ETC is behind in utilizing NADH already produced • Availability of ADP also regulates Krebs cycle activity • ADP and NAD+ are needed for reactions to occur • CO2 produced as molecules are oxidized ( H atoms are removed) • Krebs Cycle - produces • (per acetyl group-2 Carbons) • 1 GTP (ATP equivalent) • 3 NADH and 1 FADH2

  12. ETC • Electron Transport Chain (ETC) • H atoms passed down series of electron carriers by enzymatic reactions coupled to production of ATP • oxidative phosphorylation • each NADH - yields 3 ATP • each FADH2 - yields 2 ATP • for process to continue, must liberate NAD+ and FAD+ - • Process requires oxygen

  13. Aerobic Glycolysis • With sufficient oxygen pyruvate moves into mitochondria • Monocarboxylate transporter • law of mass action • 1 mole glycogen - • glycolysis • 2 moles pyruvate ; 3 moles ATP • 2 moles NADH (6 moles ATP after ETC) • Krebs - per pyruvate molecule • 4 moles NADH (one from PDH) • 12 ATP • 1 mole FADH2 • 2 ATP • 1 GTP • Multiplied by 2 = 30 moles of ATP • 39 ATP per mole of glycogen

  14. Fat Metabolism • Fat and Protein only oxidized • No anaerobic metabolism • Fatty acids - 16-18 carbon units • acetyl groups (2 carbons) broken off chain to enter Krebs cycle one at a time • Beta oxidation Fig. 2.15 • uses 1 ATP for first two carbons only • produces 1 NADH and 1 FADH2 • acetyl co-A through Krebs/ETC • Yields 12 ATP • total of 16 ATP for first acetyl group • 17 for each remaining acetyl group • last acetyl group only 12 ATP- as it is not produced by beta oxidation • 1 mole of palmitic acid-138 of moles ATP • Key enzymes - B-HAD, and lipases

  15. Comparing the Energy Systems • Table 2.6 • energy capacity - amount of ATP able to be produced independent of time • power - rate of production - time factor • *aerobic - table represents availability from glycogen only - fat is unlimited • Rest • aerobic - supplies all ATP • mainly fats and carbohydrates • some lactate ~10 mg/dl in blood • does not accumulate, but LDH active

  16. Exercise • Both anaerobic and aerobic • relative contribution to ATP production depends on • intensity and/or duration • state of training • Dietary factors (replenishment of stores) • Energy contribution vs time • (*Assumes all out activity for time frame ) • Mcardle, Katch and Katch - Exercise Physiology • Immediate - phosphagens - major contributor for up to 10 sec • Anaerobic Glycolysis - majro contributor for 30sec - 2.5 min • Aerobic metabolism major contributor for 3 min onward • Contribution of energy systems is a continuum, not an on or off situation

  17. Experimental evidence • Two types of exercise compared in most of the following experiments • near maximal - short duration • sub maximal - longer duration • Fig 2.18 glycogen depletion • activities below 60 % (VO2 max) and above 90% - limited glycogen depletion • At 75% significant depletion - leading to exhaustion (fatigue) • 2.18b • rate of depletion dependant on demand • Volume of depletion related to duration

  18. Short duration • 2-3 minutes high intensity exercise • fig 2.19 - major energy source CH2O • ATP and PC will drop rapidly • restored in recovery (rapidly) • Aerobic contribution limited by its low power output • also takes 2-3 min to increase output • oxygen deficit - period during which level of O2 consumption is below that necessary to supply all ATP required by exercise demands • ATP supplied by anaerobic systems to make up for aerobic shortfall • rapid accumulation of lactate • 200 mg/dl in blood / muscle

  19. Prolonged Exercise • 10 minutes or longer • Aerobic fat and carbohydrate metabolism are main sources of ATP • CHO dominate up to ~ 20 min • fats minor but supportive role • after ~1 hr fats become dominant source of ATP • at lower intensities (< 60% Hr max) fats also have greater contribution • fig. 2.20 • fatigue not associated with lactate, other factors - discussed later in semester • Fig 2-22 activities require blend of anaerobic and aerobic systems • energy continuum

  20. Control and Regulation • Matching provision of ATP to demand is needed so performer does not experience early or undue fatigue • Enzymes, hormones, substrates interact to modify flow through metabolic pathways of each system • Table 2.7 • Flow through different pathways is often modified by activating and inactivating key enzymes • Influences over enzymes include; • high vs low energy state of cell(NAD+) • Hormone levels (epinephrine, glucagon) • “amplification” of hormone effects • competition for ADP (between enzymes) • adequacy of oxygen supply • power output requirements relative to aerobic power (demand)

  21. Regulation • In general we observe; • regulation within muscle cell, • And influences from outside the cell • both serving to modify regulatory enzymes in each pathway • Fig 2.23 • Energy State regulation • ADP/ATP ratio • very quick - tightly linked to rate of energy expenditure • Hormone Amplification • cAMP 2nd messenger systems - amplification • Ep and Glucagon - activate phosphorylase - glycogen breakdown • lipase - fat breakdown

  22. Regulation • Substrates - • eg. NADH - buildup • In cytosol stimulates LDH - frees NAD+ • occurs when ETS is maximized • can not oxidize NADH fast enough • Also inhibitory in Krebs cycle (DH’s) • eg. Inc Pyruvate • stimulates PDH - entry into Krebs • PDH also influenced by phophorylation • Oxidative State Regulation • O2 and ADP availability • O2 stimulates cytochrome oxidase (CO) • final step in ETC • low O2 - inhibits Cytochrome Oxidase • Leads to build up of NADH, FADH2 • key factor is oxygen availability vs demand for ATP utilization

  23. Recovery from Exercise • Ch. 3 • process of recovery from exercise involves transition from catabolic to anabolic state • breakdown of glycogen and fats to replenishment of stores • breakdown of protein to protein synthesis for muscle growth and repair • Our discussion of recovery will include; • oxygen consumption post exercise • Replenishment of energy stores • Lactate metabolism(energy or glycogen) • Replenishment of oxygen stores • intensity and activity specific recovery • guidelines for recovery

  24. Recovery Oxygen • Recovery O2 - Net amount of oxygen consumed during recovery from exercise • excess above rest in Litres of O2 • Fast and Slow components • Based on slope of O2 curve • first 2-3 min of recovery - O2 consumption declines fast • then declines slowly to resting • Fig 3.1 • Fast Component - first 2-3 minutes • restore myoglobin and blood oxygen • energy cost of elevated ventilation • energy cost of elevate heart activity • replenishment of phosphagen • volume of O2 for fast component = area under curve • related to intensity not duration

  25. Recovery Oxygen • Slow Component • elevated body temperature • Q10 effect - inc metabolic activity • cost of ventilation and heart activity • ion redistribution Na+/K+ pump • glycogen re-synthesis • effect of catecholamines and thyroid hormone • oxidation of lactate serves as fuel for many of these processes • duration and intensity do not modify slow component until threshold of combined duration and intensity • After 20 min and 80% • We observe a 5 fold increase in the volume of the slow component

  26. Energy Stores • Both phosphagens (ATP, CP) and glycogen are depleted with exercise • ATP/CP - recover in fast component • measured by sterile biopsy, MRS • rate of PC recovery indicative of net oxidative ATP synthesis (VO2) • study of ATP production • 20-25 mmol/L/min glycogen and all fuels • during exercise • CP can drop to 20%, ATP to 70 % • CP lowest at fatigue, rises immediately with recovery • Fig 3.2 - very rapid recovery of CP • 30 sec 70%, 3-5 min 100% recovery

  27. Phosphagen Recovery(cont.) • Fig 3.3 • occlusion of blood flow - no phosphogen recovery • ** requires aerobic metabolism • estimate 1.5 L of oxygen for ATP-PC recovery • Energetics of Recovery • Fig 3.4 • breakdown carbs, fats some lactate • produce ATP which reforms CP • high degree of correlation between phosphagen depletion and volume of fast component oxygen • Fig. 3.5 • anaerobic power in athlete related to phosphagen potential - Wingate test

More Related