U3AoS2 - Oxygen Uptake and Acute Responses Flashcards
Oxygen uptake at rest
Minimal oxygen consumption as ATP demand is low.
Oxygen consumption at rest
0.3 L of oxygen per minute
What fuel substrates are used at rest?
Carbohydrates and Fats
The amount of oxygen entering the bloodstream is…
Proportional to the amount used by tissues for oxidative metabolism
What happens to oxygen consumption as intensity increases?
As intensity increases, consumption of oxygen increases for greater ATP resynthesis.
As the athlete moves from rest and into activity
O2 uptake increases as the body attempts to meet oxygen demand.
- Cardiovascular and respiratory systems increase O2 uptake and transport
Muscles
utilize and consume oxygen
Transition from rest to exercise
Shortfall between the amount of O2 required for exercise and amount supplied.
This is called oxygen deficit
Oxygen deficit
- Oxygen demand exceeds oxygen supply
- Anaerobic systems will be dominant
- Once oxygen becomes available to meet demand, steady state is reached.
Why does oxygen deficit occur?
Respiratory and Cardiovascular system take time to adjust to the new oxygen demand.
- Amount supplied lags behind amount needed
Steady state can only be reached when
Necessary adjustments are made to increase oxygen supply
Increased:
- respiratory frequency
- tidal volume
- heart rate
- stroke volume
Steady State
Oxygen supply meets oxygen demand
- aerobic steady state
- ATP supplied aerobically
- Heart rate and oxygen consumption remain constant
- No need for further increase oxygen uptake and little reliance on anaerobic pathways
How long does it take for steady state to be reached?
One minute or more depending on intensity for oxygen supply to increase sufficiently to meet oxygen demands.
Physiological response during Steady State
- coincides with a plateau in heart rate and ventilation as enough oxygen is reaching the working muscles
If intensity increases again
- demand for ATP and oxygen uptake increases
- short delay before O2 uptake increases sufficiently
- anaerobic systems briefly increase contribution until another steady state reached.
A steady state can only be reached when
Lactate production is less than lactate removal.
- Steady states can only be help up to and including Lactate Inflection Point
Oxygen deficit in trained athletes
Oxygen deficit is reduced due to athletes attaining steady state sooner.
EPOC stands for
Excess post-exercise oxygen consumption
EPOC
Body is taking up, transporting and consuming more O2 than is required at low intensities
Consuming more O2 as it is trying to return the body to pre-exercise state
Fast Part
First 3 minutes
- Resynthesize PC and ATP
- Restore O2 to the myoglobin
Slow Part
Following 3 minutes
- oxidation of hydrogen ions
- convert lactic acid to CO2 and H2O
- return core temperature, HR and V to pre-exercise levels
- Convert lactic acid to glycogen
Factors affecting duration of EPOC
- duration
- intensity
- fitness levels
The greater the intensity the greater the EPOC
Impact of training on O2 deficit, steady state and EPOC
- lower HR
- faster recovery
- improved ability to transport O2
- reach steady state faster
Anaerobic activities
- increased oxygen deficit and EPOC
Acute Responses
- Body responds physiologically to meet increased energy demand
- Immediate short-term responses that last only the duration of activity and recovery
- Dependent on duration, intensity and type of activity
Acute responses can be observed in
Respiratory, cardiovascular and muscular systems
- coordinated response to meet increased energy demand
The 3 systems work together to
- supply more energy, ATP and oxygen
- Remove any waste products (CO2 and metabolites)
Respiratory system
Designed to facilitate an increase in availability of oxygen and removal of CO2.
Respiratory Acute Response
Increased
- Respiratory rate
- Tidal volume
- Ventilation
- Pulmonary diffusion
- Oxygen uptake
Ventilation
How much air we breathe in and out per minute
Tidal volume x Respiratory rate
Respiratory rate
Number of breaths per minute
Tidal volume
How much air is inspired and expired in one breath
L/breath
Increased ventilation mechanism
- Beginning exercise causes receptors in the muscles stimulate an increase in ventilation
- Triggered by an increase in CO2 and Heat in the blood
- Process controlled by respiratory control system in the brain
Ventilation during submaximal activity
RR, TV and V all increase quickly then plateau
- Relationship between VO2, and intensity is linear
- Air is able to enter the lungs, diffused and transported.
Ventilation at Maximal intensities
- Tidal Volume Plateaus
- Any further increase in ventilation is due to an increase in Respiratory rate
- At progressive higher intensities, ventilation increase is not in proportion to VO2 or intensity
Why is it important to increase oxygen uptake?
Increasing oxygen means more ATP can be resynthesised aerobically
- Produces a greater amount of ATP
- Less fatigue
Increasing respiratory rate
More air entering the lungs, more oxygen
Increased Tidal Volume
More oxygen into the lungs
- greater opportunity for O2 to be diffused into capillaries
Anticipatory response to exercise
Heart rate rises above resting levels just before exercise
Due to the release of epinephrine
Benefit of the anticipatory response
Smaller oxygen deficit period, reach a steady state faster
Increased pulmonary diffusion occurs as
the surface area of the alveoli increases during exercise as a result of increased tidal volume.
Diffusion
Gases move from high concentration to low concentration
Pulmonary diffusion
- Exercise increases the rate of gas exchange allowing more oxygen into the bloodstream
Inspiration
Oxygen moves from high concentration in the alveoli to low concentration in the blood.
Expiration
Carbon dioxide moves from high concentration in the venous blood to low concentrations in the alveoli
Benefit of increasing pulmonary diffusion
- Increased delivery of oxygen and removal carbon dioxide and metabolites at higher intensities.
- enables higher aerobic intensities
Cardiovascular system
Heart, blood and blood vessels (arterioles, veins and capillaries)
Role of the cardiovascular system
Delivers blood carrying oxygen to the muscle and assists in removal of carbon dioxide.
Cardiovascular system acute responses
Increased
- heart rate
- stroke volume
- cardiac output
- blood pressure (no performance benefit0
- avo2 difference
redistribution of blood flow.
Stroke volume measurement
mL/beat
Heart rate measurement
beats per minute
Cardiac output
L/min
Cardiovascular responses performance benefit
- Deliver greater oxygen and substrates to meet increased ATP demands
- More blood speeds up carbon dioxide and waste product removal
Focus: deliver O2 to the working muscles
Stroke volume definition
mL of blood pumped out of the left ventricle per beat
Heart rate definition
Number of times the heart contracts per minute
Cardiac output
L of blood ejected from the left ventricle per minute
Maximum heart rate formula
220 - age
Resting heart rate
Number of heart beats per minute while the body is at rest
Average resting heart rate
60 - 80 bpm
Heart rate response to exercise
Stroke volume and Heart rate increases as a response to the extra energy required by the body to increase Q
- Increases linearly in exercise intensity until near maximal intensities
Increased heart rate benefit
- helps increase oxygen and fuel delivery and aids removal of waste
How much blood is ejected from the heart at rest
40 - 60% blood in the left ventricle
Most important factor of cardiac output
Heart rate
- during submaximal HR increases until O2 demands are met
- will then plateau when steady state reached
Heart rate of trained athletes
Lower Heart rates as the have greater stroke volumes so the heart beats less frequently to deliver the same blood amount
Stroke volume response to exercise
- increases
- will plateau at submaximal intensities then remain unchanged
- occurs so more blood can be ejected and more oxygen delivered to muscles
Stroke volume of an untrained athlete
At rest 60-80ml
Exercise 110 - 130ml max
Stroke volume of a trained athlete
Rest 80 - 110mL
Exercise 160 - 200mL per beat
- Increased stroke volume at all intensities, decreased heart rate at rest and submaximal intensities
Increased Q at maximal due to Increased SV
Cardiac output formula
Stroke volume x Heart rate
Cardiac output response
Increases rapidly during the first 2 - 3 mins and then gradually due to increased SV and HR
Increases delivery of oxygen to the muscles
Maximal intensity cardiac output
Untrained 20 - 25 L/min
Trained 35 - 40 L/min
Advantage of increased cardiac output
- Increased intensity with less physiological strain
- More blood can be ejected out of the heart per minute: Increased blood flow and O2 supply, ATP rebuilt faster and higher aerobic intensity
Blood pressure
Pressure exerted by blood against arterial walls as it is forced through the circulatory system by the action of the heart
Systolic blood pressure
- Pressure recorded as blood is ejected during the contraction phase of the heart beat (left ventricle)
Unit: mmHg (pressure)
Diastolic blood pressure
Recorded as blood is ejected during the relaxation phase
- Usually 80
- Stays relatively stable during exercise
Normal blood pressure
120/80 mmHg
Mechanism for increased blood pressure
- Cardiac output increases with increasing intensity
- Blood pressure will increase
- Systolic BP increases more than diastolic blood pressure
- Arteries will vasodilate to enable greater volume of blood to be delivered
Resistance training
Greater increase in BP than endurance training
Redistribution of blood flow at resting conditions
15 - 20% total blood flow directed to skeletal muscles
80 - 85% to the major organs eg. Heart, liver and kidneys
Redistribution of blood flow during exercise conditions
80 - 90% redirected to working muscles
Achieved by capillaries and arterioles expanding in diameter (vasodilation)
- Blood flow to organs and inactive areas reduced by vasoconstriction
Vasoconstriction
Narrowing of vessels, constricting blood flow
Decreased blood and O2 delivery
Vasodilation
Vessels opening, increased blood flow and delivery
Areas blood distributed away from
Non-essential organs
- Enable increased blood and O2 to working muscles as intensity increases
- Blood flow to skin increases to regulate body temperature
Increased venous return
Increases through muscle pump, respiratory pump and venoconstriction
One way valves
Prevent back flow
Decreased blood volume
Plasma in blood is lost as sweat in attempt to cool the body.
Depends on intensity, duration and environmental factors.
Muscular responses vary depending on
Muscle fibred recruited, type, intensity and duration of the activity
Muscular responses
Increased
- motor unit and muscle fiber recruitment
- blood flow to muscles
- AVO2 Difference
- muscle temperature
- oxygen supply and use
Decreased muscle substrate levels
Motor units
Way in which muscles are controlled by the CNS
A motor neuron and muscles fiber stimulated
Increased motor unit and muscle fibre recruitment
Increase must take place
- More muscle fibres are activated to contract at higher intensities.
Nervous system
Increases no. of motor units recruited and speed of motor units recruited.
Results in greater force, power and strength development
Muscle fibre example
Heavy squat = increased number of motor units recruited
Squat jump = increased speed of recruitment
Increased blood flow to muscles
- Greater blood flow directed towards working muscles
- Achieved through vasodilation to the capillaries surrounding the muscle and redistribution blood flow from the non-essential organs towards working muscles to increase o2 delivery
Benefit of increased blood flow to muscles
- work at higher intensities due to greater amount of blood and O2 delivered and consumed by the muscle to produce ATP aerobically
AVO2 difference
arteriovenal oxygen difference
Difference in O2 levels between blood in arterioles compared to blood in veins
Amount of oxygen extracted from the blood and consumed by the muscles
Increased AVO2 difference
Larger during exercise as muscles require more O2
Mechanism for increased AVO2 difference
- vasodilation at muscle vessels as direct result from increased Q
- increased oxygen demand with increased intensity
Advantage of increased AVO2 difference
Increased consumption of O2 by the muscle enables athletes to work at higher aerobic intensities
Increased muscle enzyme activity
Oxidative, Glycolytic, ATPase and Creatine Kinase
Increased muscle temperature
- Resynthesis of ATP aerobically results in increase muscle and core temperature
- Metabolic activity also increases temperature
Regulated through sweat produced by sweat glands
Oxidative enzymes
Assist in metabolizing fats and glucose in the muscle
Speeds up aerobic ATP resynthesis rate
Glycolytic enzyme
- Speed up glycogen breakdown via anaerobic glycolysis
- Speeds up ATP resynthesis
Increased metabolites
Blood lactate will increase until steady state
All or nothing principle
When a motor unit is activated, it will contract maximally or not at all.
VO2
Amount of oxygen being consumed to meet the demands of exercise
- Dependent on the ability of muscles to take up and consume CO2 and cardiovascular and respiratory systems to deliver
VO2 max
- Highest VO2 obtained during incremental tests to exhaustion
- At this point VO2 will not increase despite additional intensity increase
In order to test VO2 max
- perform work involving large muscle groups
- incremental and progressive
- Increase workload by increasing speed and gradient
Initial stages of VO2 max testing
Ventilation and cardiac output increase to deliver O2 to working muscles
O2 consumption increases while working anaerobically
After 30 seconds ATP replenished aerobically steady state
Increasing the intensity of the test
- Increases ATP and O2 demand
- initially met by supplying ATP anaerobically
- Aerobic is still the main contributor
- Another o2 deficit
- New steady state is reached when cardiorespiratory systems adjust to meet new demands
Lactate produced during O2 deficit
will be oxidised
Intensity will increase until
- New steady state cannot be reached
- metabolites no longer oxidized
- lactate production exceeds removal
- H+ ions accumulate
- Ventilation increases in attempt to expel increased CO2
Sedentary people
LIP is at a lower % of VO2 max
Endurance athletes VO2
- Higher VO2 max and LIP
- produce less hydrogen ions, work at higher aerobic intensities for longer
How long does VO2 max testing last for?
8 - 14 minutes depending on aerobic capacity
Aerobic capacity
Total amount of energy obtainable from the aerobic energy system
Aerobically fit athletes
Work at higher intensities without hydrogen accumulation due to increase contribution from the aerobic system
Untrained athletes VO2
Increased anaerobic contribution when intensity increases therefore fatiguing earlier
VO2 Max definition and formula
Maximum amount of O2 that can be taken up, transported and used by the body in 1 minute for the purpose of aerobic energy production
Q x AVO2 diff
Absolute VO2 Max
ml/min
- does not take body weight into consideration
- cannot be compared with other athletes
- straight measure of how many mL of oxygen consumed per minute
Relative VO2 max
ml/kg/min
- considers body weight
- same absolute VO2 max, lighter person has higher relative
- enables comparisons
Factors affecting VO2 max
- gender
- body size
- genetics
- age
Gender
Females have:
- lower blood volume and hemoglobin
- lower O2 carrying capacity
- Lower lung volume and left ventricle decreasing TV and SV
- Increased body fat % and decreased muscle tissue. Body fat does not use O2.
Body size
- larger heavier person requires more O2
- more muscle and tissue to consume O2
Genetics
O2 uptake varies 20 - 25%
- % of slow twitch fibres main reason, increased ability to consume O2
Age
Maximal O2 uptake declines 1% every year after 25
- training reverses decline
- decline due to decreased SV and HR and vessel elasticity
VO2 training
Aerobic
- continuous, fartlek, long interval
Increases O2 uptake due to chronic adaptations and improves VO2 max
Ventilation why it changes
- To improve volume of oxygen in the lungs that can be diffused into the blood and transported to the working muscles
Venous return
The amout of blood that is returned to the heart via the veins
Muscle pump
Muscular contractions compress veins, pushing the blood through the veins back to the heart.
Respiratory pump
When venous return needs to increase, respiratory rate increases as the diaphragm increases abdominal pressure, forcing blood back to the heart
Venoconstriction
Reduces the capacity of the veins forcing the blood to be pushed up to the heart
Venous return why is changes
Takes place so there is an increase in cardiac output
Results in more blood being delivered back to the heart so more oxygenated blood can be pumped back out to the working muscles
