Acute responses Flashcards
Acute responses
Whenever an individual engages in exercise, the body responds physiologically to meet the increased energy demands of the activity. The respiratory, cardiovascular and muscular systems respond and undergo changes to meet the new demand for energy
- These immediate short term responses that last only for the duration of the activity are called acute responses
Oxygen consumption (VO2)
The volume of oxygen taken up by the body, transported and utilised by the body
VO2 Max
the maximum amount of oxygen that can be taken up, transported and utilised by the body per minute
Why do we have acute responses
Several of our acute responses contribute towards oxygen consumption. The greater the intensity, the greater the response until VO2 max is reached. This is good for us because as we exercise, out oxygen consumption increases, allowing us the meet oxygen demand and ultimately allowing us to meet ATP demand that increases with exercise intensity.
Relationship between oxygen consumption and exercise intensity
There is a linear relationship between oxygen consumption and exercise intensity, as exercise intensity increases, oxygen consumption increases to meet the oxygen and ATP demand.
Respiratory Response
The respiratory system is responsible for the delivery of oxygen to and carbon dioxide from the cells of the body
Ventilation
Refers to how much air is breathed in and out on one minute. Product of tidal volume and respiratory rate.
- measured in L/minute
Tidal Volume
How much air is inspired or expired in one breath
-measured in L/breath
Respiratory Rate
The number of breaths taken in one minute
- measured in breaths/minute
Ventilation and exercise
As exercise commences, ATP demand increases and oxygen requirements increase as well. Increases in ventilation will then come about from increases in respiratory rate and tidal volume. As ventilation increases, this increases the oxygen volume in the lungs which can be then transported around the body
Ventilation and exercise - submaximal and maximal
Submaximal exercise: tidal volume and respiratory rate increase proportionally in order to increase ventilation.
High intensity exercise: at higher intensities, tidal volume will plateau, at this point any further increases in ventilation are due to increases in respiratory rate
Ventilation and oxygen consumption
Ventilation and oxygen consumption are different concepts because oxygen only makes up 21% of air, however they share a relationship
Relationship between ventilation and oxygen consumption
Ventilation and oxygen consumption share a linear relationship. The point where ventilation no longer increases linearly with oxygen is called the ventilatory threshold. Beyond this point, oxygen delivery to muscles becomes a limiting factor and body is forced to rely more upon its anaerobic pathways
Pulmonary diffusion
is where gaseous exchange takes place within the lungs. Pulmonary diffusion has two major functions:
- replenish oxygen supply through diffusion from alveoli to pulmonary capillaries
- remove carbon dioxide from returning venous blood
Pulmonary diffusion and exercise
when we begin to exercise, the diffusion capacity is increased due to the surface area of alveoli and muscle tissue. Increased pulmonary diffusion allows oxygen and carbon dioxide to be exchanged.
Cardiovascular system
Responsible for the circulation of blood around the body. When we begin exercising the focus is on getting more blood to the working muscles to deliver oxygen and speed up the removal of waste
Cardiac output
refers to how much blood is pumped out of the heart in one minute
- product of stroke volume and heart rate
Stroke volume
How much blood is ejected by the left ventricle per beat (L/beat)
Heart rate
Number of heart beats in one minute
- measured in beats/minute
Cardiovascular responses
- when we begin exercising stroke volume and heart rate begin to increase with cardiac output allowing an increase in oxygen being delivered to the working muscles
- At submaximal intensities, stroke volume will plateau as the left ventricle has reached its maximum capacity and any increases in cardiac output is due to increase in heart rate
- At periods of steady state, heart will level off as oxygen supply is meeting demand
- With further increase in intensity beyond this, heart rate will increase linearly with intensity until maximum heart rate is reached. After this point we will see not further increases in cardiac output
Venous returns
- The flow of blood back to the heart
- The heart can only eject how much blood is in its ventricles so it is important for an increase in cardiac output to be accompanied by an increase in venous returns
Increasing venous returns
Three mechanisms increase venous returns
- The muscle pump: Due to repetitive muscular contractions, veins in between muscles are squashed together and the blood within them is forced back into the heart
- The respiratory pump: when we breathe in, the diaphragm increases abdominal pressure and the veins in this area get squashed and the blood in them gets forces back towards the heart
Venoconstriction: reflex controlled by the central nervous system, the capacity of the venous system forces the blood in the veins to be forced back into the heart
blood volume
During aerobic exercise, blood volume will decrease
- Water in plasma is lost from sweating during exercise to maintain a constant temperature. The volume of blood decreases as a result depending on hydration and temperature.
During anaerobic exercise, blood volume will remain mostly unchanged because of the short duration of anaerobic exercise, the body doesn’t need to sweat much
Redistribution of blood
At rest, 80% of cardiac output is directed to organs like the brain and digestive system. During exercise, 80% of blood is redirected to working muscles.
This occurs through vasoconstriction of arterioles leading to other organs and vasodilation of arterioles leading to working muscles, allowing more blood and therefore oxygen and fuels to reach the muscles
Vasoconstriction
Decrease in diameter of blood vessels, resulting in decrease in blood flow to the area supplied by the blood vessels
Vasodilation
An increase in diameter of blood vessels resulting in an increased blood flow to the area supplied by the blood vessels
Blood pressure
Pressure exerted by the blood against arterial walls as it is forced through the circulatory system by the action of the heart
Systolic blood pressure
Blood pressure recorded as blood is ejected during the contraction phase of the heart cycle. It is the higher of the two blood pressure values. When exercising blood is pumped more forcefully and quickly out of the heart, increasing pressure on artery walls which increases systolic pressure
Diastolic blood pressure
Blood pressure recorded during the relaxation phase of the heart cycle. Lower of the two blood pressures. Diastolic blood pressure remains relatively unchanged during exercise
A-vO2 diff
Arteriovenous oxygen difference: The difference in oxygen concentration in the arterioles compared to the venules: is a measure of how much oxygen the muscles are extracting from the blood
A-vO2 diff during exercise
A-vO2 diff increases as there is a greater difference between the arterioles and venules as the muscle is taking more oxygen when exercising
- At rest, arterial blood releases as little as 25% of its oxygen content to the muscle tissue. The remaining 75% of oxygen returns to the heart in venous blood
- During exercise, the working muscles extract greater amounts of oxygen from the blood as it passes through. This increases the a-vO2 difference
Increased blood flow to working muscles
As part of redistribution of blood flow during exercise, blood is directed away from non-essential organs and redirected to the working muscles
The increased blood flow to the working muscles allows for a greater delivery of oxygen to meet the increased ATP demands that come with exercise
Motor unit
- a motor neuron and the muscle fibres it stimulates. The central nervous system uses motor units to talk to the muscles to control muscular contractions
- Motor units contract through an all or nothing principle (they contract or they don’t) this means not all motor units are used for certain activities
Motor unit and exercise
During exercise, the required amount of force needed from a working muscle increases.
Motor unit recruitment increases when we begin exercising to increase force production:
- signals for more motor units to work
- signals to activate the motor unit more often
Increased muscle temperature
Increased blood flow to the muscles, coupled with the heat generated as a by-product of the increased production of ATP during exercise, results in an increased in muscle temperature
Increased metabolic by-products
During anaerobic dominant events, there will an accumulation of by products. In anaerobic glycolysis, there’s a build up of H+ ions and in ATP-PC system, inorganic phosphate build up
- Both will inhibit muscular contractions and will inhibit performance
Decreased energy substrates
As intensity of exercise increases out ATP demand increases and therefore our need for fuels increases,
Exercise causes a decrease in muscle substrates.
Muscular stores of ATP, creatine phosphate, glycogen and triglycerides begin to deplete during exercise because they are sources of fuels for the production of ATP
The depletion of these stores will vary depending on duration and intensity
