Chapter 7: Acute Responses to Exercise Flashcards
Acute responses to Exercise
short term physiological change to help meet the demands of exercise
- When exercise increases, there is an increase demand of the cardiovascular, respiratory and muscular systems
- The level of response is dependent on the intensity and type of exercise being undertaken
Respiratory Responses
Increased Ventilation
Increased Respiratory Rate
Increased Tidal Volume
Increased Pulmonary Diffusion
Increased Pulmonary Diffusion
increasing the transfer of oxygen from the alveoli to the capillaries
- The molecules move down the concentration gradient(high to low)
Functions of pulmonary diffusion:
- To provide the blood with oxygen from the lungs via the alveoli
- To remove carbon dioxide from the blood to be exhaled
Increased Ventilation
increasing the volume of air breathed in per minute
- V = TV x RR
Increased Respiratory Rate
increasing the number of breaths per minute
- Linearly increases alongside exercise intensity
Increased Tidal Volume
increasing the Volume of air breathed in per breath
- Measured in Litres - Plateaus at sub-max intensity
Cardiovascular Responses
- Increased Heart rate
- Increased Stroke Volume
- Increased Cardiac Output
- Increased Blood Flow to Working Muscles, the heart and the skin
- Decreased Blood Flow to digestive tract
- Increased AVO2 Difference
- Decreased Blood Plasma Volume
- Increased Systolic Blood Pressure(doesnt benefit)
Increased Heart Rate
increasing the number of beats per minute
- Increases linearly with exercise intensity
Increased Stroke Volume
increasing the volume of blood pumped per heart beat
- Increases with exercise intensity until it reaches 60% of VO2 max where it plateaus
Increased Cardiac Output
increasing the Volume of blood pumped by the heart per minute
- Q = SR x HR - Measured in Litres/minute
Increased Systolic Blood Pressure
blood pressure on artery walls when the heart contracts
- Increased Q causes an increase in blood pressure
- Exercise involving full body movements results in an increased systolic pressure while the diastolic remains relatively constant
Mechanisms to redistribute blood flow
- Vasodilation: the widening of arterioles which allows more blood to flow through
Vasoconstriction: the tightening of arterioles which allow less blood to flow through
Blood Flow During Exercise
- Vasoconstriction occurs in the arterioles supplying the kidneys, digestive system and inactive muscles
- Vasodilation occurs in the arterioles supplying the working muscles and the heart to increase oxygen supply
- Also occurs in the arterioles supplying the skin to help remove heat(thermoregulation)
- Blood flow to the brain is maintained
Increased AVO2 Difference
increasing the difference in oxygen concentration in the arterioles compared with the venules
- Measures how much O2 diffuses from the capillaries into the muscle
- At rest it can be as little as 25% of O2 diffuses
- At high intensity exercise, it can be as much as 75% of O2 diffuses
- E.g. at rest there could be 20mg in the arteries and 15mg in the veins meaning the AVO2 Difference is 5mg
- During exercise, it could be 20mg in the arteries and 5mg in the veins meaning the AVO2 difference is 15mg
Venous Return
the blood returning to the heart and lungs from the body
- Increases during exercise through a mechanism called a 'muscle pump"
Mechanisms to increase Venous return
Venous return via a muscle pump:
- As the muscles contract, they squeeze blood vessels and push the blood back towards the heart and lungs
- Due to the addition of one way valves inside veins, blood can only travel one direction
Venous return via a respiratory pump:
- When intercostal muscles contract and relax during the inspiration and expiration process, they compress the nearby veins and assist blood return to the heart.
Venous return via veinoconstriction:
- Constriction of the smooth muscles around the veins which unconsciously force blood flow after exercise
Decreasing Blood Volume
the decreasing amount of fluid circulating within the circulatory system
- During exercise, blood volume decreases due to plasma decreasing becoming more viscous(thick)
- Plasma decreases when blood flows to the skin to remove heat through the evaporation of sweat
Components of Blood:
- Plasma(water, nutrients and blood proteins) = 55%
- White blood cells and platelets = <1%
- Red blood cells = 45%
Factors determining the volume of blood loss
- Exercise intensity
- Environmental factors - e.g. temperature
- Level of hydration
Muscular Responses
- Increased Motor unit recruitment
- increased muscle temperatures
- Increased Oxygen uptake(VO2)
- Increased muscular enzymatic activity
- decreased energy stores
- increased accumulation of Metabolic by products
Increased Motor Unit recruitment
increasing the amount of both the motor neuron and the muscle fibres they control/are attached to
- ST fibres are activated during all contractions and then depending on exercise intensity, duration and fatigue FTA and FTB may be recruited.
Motor Unit Recruitment Order:
- Smaller slow Twitch Fibres(ST)
- Fast Oxidative glycolytic fibres(FTA)
Larger fast glycolytic fibres(FTB)
Increased Muscle Temperature
As exercise commences, there is an increase in the rate of metabolism to produce ATP aerobically, causing an increase in muscle temperature
- Heat is a by product in the electron transport Chain(aerobic ES)
Changes to accommodate increased muscle Temperatures:
- Stimulating the sweat glands in the skin to produce sweat leading to a decrease in blood flow
- Increased blood flow to the skin allows the blood to be cooled off by the external environment
Increased Oxygen Uptake
increasing the volume of the oxygen used by muscles which will increases as exercise intensity increases
- Will continue until the VO2 max is reached(when anaerobic energy system must contribute to provide the remaining energy)
Ways to Increase VO2 Max
- Increase Cardiac Output(Q)
- Increase A-V O2 difference
- Increased Tidal Volume
- Increased respiratory Rate
- Increased Ventilation
- Increased stroke volume
- Increased Heart Rate
- Increased pulmonary diffusion
Enzymes used during Exercise
- ATPase: an enzyme which assists in the breakdown of ATP to release energy for muscular contractions
- Glycolytic enzymes: assist in the breakdown of glucose to release energy for ATP replenishment.
- Oxidative Enzymes: help break down glycogen and fats more effectively in the presence of O2
Decrease in Energy Fuels
all available fuel sources within the muscle decrease as exercise is undertaken
- The duration and intensity of exercise will determine which fuels and fibre types are preferentially used and therefore the impact on the degree of fuel use
Fuels:
- ATP
- Glycogen
- PC
- Fats
Increased Accumulation of Metabolic By Products
- Occurs in high intensity exercises occurring between 5 and 75 seconds long(using the anaerobic ES)
- As exercise begins, lactate and H+’s begin to build up due to the production of ATP anaerobically.
- At sub-max intensity, there is an increase in lactate and H+ until the steady state is achieved at which lactate and H+ are being removed at the same rate as they are being produced
- As soon as the exercise proceeds past the lactate inflection point, where the lactate and H+ production is above the rate from which it can be removed, a steady state can no longer be reached and the athlete will need to decrease their intensity
Lactate Inflection Point
the final point of lactate steady state where H+ and lactate are being produced faster than they can be removed
- Usually triggered at 85% of max HR
