1 Kin 310 Exercise/Work Physiology Office hours - K8629 Mondays and Wednesday 10-11 am –or by...

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Kin 310Exercise/Work Physiology

• Office hours - K8629• 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/kin310.htm

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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 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

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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

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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

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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

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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

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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

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Anaerobic Glycolysis

• Lactate produced when low O2 – 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

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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, FADH2

– 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 H2O

• occurs in mitochonrial membrane system - cristae

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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

• CO2 produced as molecule breaks down and H are removed– oxidation - removal of electrons

– reduction - addition of electrons

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Krebs Cycle• Krebs - 2 GTP produced

– 6 NADH and 2 FADH2

• 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 FADH2 - 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

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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 FADH2

– 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

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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

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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

• 2.18b - rate of depletion dependant on demand

– total depletion related to duration

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Short duration

• 2-3 minutes high output exercise• fig 2.19 - major energy source CH2O

– 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 O2 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

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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

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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

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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– cAMP 2nd messenger systems -

amplification

– Ep and Glucagon - activate phosphorylase - glycogen breakdown

– lipase - fat breakdown

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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– O2 and ADP availability

– stimulates cytochrome oxidase

– final step in ETS

– low O2 - inhibits CO - build up NADH, FADH2

– key factor oxygen availability

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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

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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 - O2

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

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Recovery Oxygen

• Slow Component– elevated body temperature

• Q10 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

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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%

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Phosphagen Recovery• Fig 3.3 • occlusion of blood flow - no

recovery• 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 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

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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

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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

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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% VO2 Max

– trained 50-60% - some studies

– glycogen re-synthesis slowed with high intensity active recovery

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Lactate and the Slow Component of O2

• fig. 3.13• Fig 3.14

– close association between slow recovery component of O2 and removal of lactate

• restoration of O2 stores– fast component - 10-80 seconds

• Ion concentrations– pH - 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)

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Performance Recovery• Regain performance - force, power• med intensity 60-80%

– fast recovery - one minute

• higher intensity bout -– longer recovery

• Aerobic fitness (high VO2 max) important influence– good correlation between fast recovery

of muscle function and VO2 max

• why?– Fast component requires O2

• Guidelines Table 3.2