Transcript Curriculum Effects - Western Michigan University

Exercise Metabolism
Concepts
Dr. Suzan Ayers
Western Michigan University
Lecture Overview
Energy production
 Oxygen supply during sustained exercise
 Measuring exercise capacity
 Cardiorespiratory system and oxygen supply
during exercise
 Human skeletal muscle cells
 Activity’s energy cost
 Dietary considerations
 Sport-specific training
NOTE: throughout this presentation, the use of
[] connotes “concentration”
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Energy Production
Adenosine triphosphate (ATP)
 3 ATP-resynthesizing energy systems
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(Fig 10.4)
Immediate energy system (stored energy, high-energy
phosphagen, ATP-PCr system) 0-30s
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Anaerobic glycolytic system (lactic acid system) 20-180s
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Aerobic or oxidative system >3 min (see Table 10.1)
All work along a continuum (fig 10.4) constantly
Body breaks down nutrients (fats, proteins, carbs) to
release energy from chemical bonds, which is then
used to synthesize ATP
Max exercise can produce 15-fold ↑ [lactic acid]
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20-40 mins required to fully remove this lactic acid build-up
Light jog @ 30-60% max pace best active recovery
Oxygen Supply: Sustained Exercise
Oxygen consumption: VO2
 O2 deficit
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Submaximal, [↔] exercise
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initial few mins of exercise, insufficient O2 uptake
ATP provided by 2 anaerobic systems
Period of adjustment for increased energy demand
VO2 steady state reached
Continually [>] exercise
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VO2 increases steadily to max value/exercise
capacity
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Supramaximal exercise (above VO2max)
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Post-exercise O2 uptake
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ATP, beyond that produced by oxidative metabolism,
produced by anaerobic glycolysis (↑ lactate levels)
EPOC: excess post-exercise O2 consumption (O2 debt)
Excess O2 removes lactate & re-synthesizes muscle
stores of glycogen, PCr and ATP
Size of EPOC depends on [exercise]/duration
VO2max: Indicator of endurance ex capacity
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Max O2 consumed/min during exercise (aerobic power)
40-50% genetically determined
May increase up to 40% w/ training
Not exclusive indicator of exercise performance
Measuring Exercise Capacity:
Aerobic or Endurance Capacity
VO2 max: measure of aerobic power
 Endurance exercise capacity: performance
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measure
Mode of testing specific to athlete’s training
VO2 max usually reached during final minute of
exercise, immediately before volitional fatigue
Major limiting factor for endurance exercise
performance is O2 delivery via the circulatory
system to the working muscles
Measuring Exercise Capacity:
Anaerobic Capacity
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Anaerobic power: max power, possible in all-out
exercise test
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Anaerobic capacity: total work accomplished in a
set time (30-60s)
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General or sport-specific tests used
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10- and 30-s cycle ergometer tests
Vertical jumping
Sprinting
Stair climbing
Both (an)aerobic tests help standardize
[exercise] for exercise prescription
Cardiorespiratory System and Oxygen
Supply During Exercise
Cardio: heart
 Vascular: blood vessels
 Respiratory: lungs and ventilation
 Aerobic: with oxygen
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Overall, HR, blood flow, & respiratory rate ↑
proportionally with ↑ [exercise]
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Blood flow
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during submax exercise, ~50-60% of blood flow is
directed to working muscles
during max exercise, ~80% of blood flow is
directed to working muscles
Human Skeletal Muscle Cells
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Fiber types are classified by
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(Table 10.2):
Physiological (activities, functions)
Biochemical (chemistry of biological processes)
Histological (microscopic structure) properties
Motor neuron determines fiber type
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I (slow oxidative): smaller, ↓ force, ↑ time, posture
IIa (fast oxidative glycolytic): large, fast, ↑ force, ↑
gylcolytic capacity, moderate: mitochondria, capillary
supply, oxidative capacity than IIb fibers
IIb (fast glycolytic): largest, fastest, most forceful, ↑
anaerobic glycolytic capacity, fatigue easily
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Fiber types activated proportionally to force
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Size principle:
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I, then IIa, then IIb (as additional force needed)
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Average human: 50% ST, 50% FT
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Proportion of fiber types varies
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Elite distance runners: 80% I, 20% II
Elite sprinters: 25-40% I, 60-75% II
Fiber types only a broad indicator of potential
Activity’s Energy Cost
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Influential factors
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Activity, intensity, mechanical efficiency
Body mass (non-supported activities-run, walk)
Environmental factors (temperature, wind, rain)
Human body, at best, 25% efficient
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Economy of movement: O2 cost of any activity
Body mass supported: energy cost independent of
body mass
Unsupported activities: energy cost rises w/ ↑ body
mass
Most energy consumptive: whole body or large
muscle group activities (swim, run)
Consider energy cost of training in development of dietary planning
Dietary Considerations
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High carbohydrate (CHO) diet ↑ muscle
glycogen stores (ergo exercise capacity) Fig.10.14
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“Hitting the wall”=glycogen depletion
24-48hr required to fully restore glycogen levels
↑ CHO diet ASAP after exercise aids repletion rate
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60-80% daily intake=CHO
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Sports drinks, fruits, breads, wheat cereals, gels
6-8g CHO/kg body wt/day
Intense training or taper times
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9-10g CHO/kg body wt/day
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Protein
Tables 10.4, 10.5
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Well-balance diet adequate for most athletes
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12-15% daily intake=protein (0.8g protein/kg/day)
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Strength/Power/Speed athletes
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1.5-2 g protein/kg body wt/day
Endurance athletes
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1.5-1.6 g protein/kg body wt/day
EXCESS PROTEIN = EXPENSIVE URINE
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Water
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70-80% energy produced during ex is heat (sweat)
Depending on factors, 0.5-3L/hr sweat can be lost
Losing 4-5% body mass impacts thermoregulation and
exercise capacity
Prolonged exercise w/o H20 replacement
Blood volume may drop significantly
 Heat loss slows/stops
 Body temp can ↑ dangerously
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Guidelines
500-1000ml pts plain H20 1hr before activity
 250-500ml 20 mins before
 250ml every 15 mins during
 Intense exercise > 60 mins: add glucose & electrolytes
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 6% glucose in solution--[low electrolyte] promotes faster H20
absorption
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Several hrs may be needed to completely replace H20
Sport-Specific Training
 Anaerobic
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Max force production (Abernathy:0-30 sec)
 Stored
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ATP and PCr, muscle glycogen breakdown
Anaerobic glycolysis
 Up
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Energy Training
to 2 min events (Abernathy:20-180 sec)
Limited support for training benefits here
 Aerobic
Energy Training
(Abernathy:0-30 sec)
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Evidence clear, dramatic, specific
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Endurance training has specific benefits
volume in muscle
 ↑enzyme activity in aerobic pathways
 ↑fiber’s ATP generating ability aerobically
 ↑# capillaries fueling each muscle fiber
 ↑intramuscular fat stores
 improves fat burning ability
 Improves muscle’s ability to access & utilize fat
 ↑mitochondrial
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Endurance training has general benefits
volume 10-15%
 ↑stroke volume
 ↑cardiac output (HR x stroke volume)
 ↑efficiency of the respiratory system
 ↑blood
 More air with fewer breaths
 Greater tidal volume
 Ventilation=tidal volume x frequency