Download Kin 310 Exercise/Work Physiology

Kin 310
Exercise/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
1
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
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 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
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, 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
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
• CO2 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 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
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 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
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
• 2.18b - 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 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
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
– cAMP 2nd 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
–
–
–
–
O2 and ADP availability
stimulates cytochrome oxidase
final step in ETS
low O2 - inhibits CO - build up NADH,
FADH2
– 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 - 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
21
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
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 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
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% VO2 Max
– trained 50-60% - some studies
– glycogen re-synthesis slowed with high
intensity active recovery
27
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)
28
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
29