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Transcript of 1 Kin 310 Exercise/Work Physiology Office hours - K8629 Mondays and Wednesday 10-11 am –or by...
1
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
2
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
3
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
4
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
5
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
6
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
7
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
8
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
9
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
10
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
11
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
12
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
13
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
14
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
15
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
16
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
17
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
18
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
19
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
20
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
21
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
22
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
23
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%
24
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
25
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
26
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
27
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
28
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)
29
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