Acute Responses To Exercise Flashcards
Acute response
A short term physiological change to help meet the demands of exercise.
when exercise commences there is an increased need for energy substrates and oxygen which the cardiovascular, respiratory and muscular systems respond to meet these demands.
Respiratory Acute responses
- Increased respiratory rate
- Increased Ventilation
- Increased Tidal volume
- increased pulmonary diffusion
Ventilation (V)
How much air is breathed in or out, increases from 5-6 L per min to over 130L when working maximally.
V= TV (how much air is inspired per breath L) x RR (no. of breaths taken in one minute)
Pulmonary diffusion
Occurs between the lungs (alveoli) and capillaries
- the movement of molecules from an area of higher concentration to lower concentration
as intensity increases, there is a greater need for oxygen, so pulmonary diffusion will increase, resulting in more O2 in the blood. Increases up to three times the resting rate.
Pulmonary diffusion functions
- To provide the blood with oxygen from the lungs via alveoli
- To remove carbon dioxide from the blood to be exhaled
Cardiovascular responses
- Increased heart rate
- Increased stroke volume
- Increased cardiac output
- increased systolic blood pressure
- redistribution of blood flow
- increased venous returns
- increased a-vO2 difference
- Decreased blood volume
Cardiac Output (Q)
The amount of blood pumped out of the heart in one minute (L per min)
increases from 5-6L to around 20-25L during maximal exercise.
Q= SV x HR
Stroke volume
The amount of blood ejected by the left ventricle of the heart per beat (L per beat)
Increases linearly until it reaches maximal value at approximately 60% of VO2 max (submax) then it plateaus
Heart rate
The number of times the heart beats in one minute.
increases linearly with increasing exercise intensity up to a maximum that is calculated by subtracting the individuals age from 220
Blood pressure
Systolic- pressure on the artery walls when the heart contracts
Diastolic- pressure on artery walls when the heart relaxes
Increased blood pressure
Increased cardiac output causes an increase in blood pressure.
Exercise involving large muscle groups results in Increased systolic
Strength and resistance training results in a greater change in both systolic and diastolic blood pressure (cardiac output will be less)
Redistribution of blood flow (Vasodilation)
It is the dilation of arterioles which allows more blood to flow through.
During exercise vasodilation occurs in the arterioles supplying working muscles to increase oxygen supply (decrease reliance on anaerobic glycolysis and decrease metabolic by products)
Occurs in the arterioles supplying blood to the skin to help with thermoregulation by removing heat.
Also occurs in the heart as it is working harder and requires a greater oxygen supply
Redistribution of blood flow (Vasoconstriction)
The constriction of of arterioles which allows less blood flow.
Occurs in the arterioles supplying the spleen, kidneys and gastrointestinal tract and inactive muscles.
Arteriovenous Oxygen difference (a-vO2)
The difference in oxygen concentration in the arterioles compared with venules.
It measures how much Oxygen diffuses from the capillaries into the muscles.
At rest, it can be as little as 25% of O2 diffused into muscle tissue, but during exercise, the working muscles extract greater amount of O2 from the blood to fuel the aerobic energy system, increasing a-vO2 difference.
Up to 75% of available o2 is extracted during high intensity exercise.
Venous returns
Refers to the blood returning to the heart and lungs from the body. Venous returns increase during exercise through different mechanisms.
Muscle/ respiratory pump [and why it is important]
Muscles continuing to contract or contracting during exercise which squeezes blood vessels and push blood back towards the heart and lungs. Respiratory pump also parallels this movement as when we breathe in it squeeze the veins around the lungs and pushes the blood back to the heart.
This is why it is essential to do active recovery (means that the muscles continuing contracting making a muscle pump) after anaerobically or aerobically exercising to ensure that the blood does not pool and is able to remove wastes and provide o2 to the muscles.
They help maintain the circulation of blood around the body.
why does Blood volume decrease when exercising and how does it have a negative impact on performance
During exercise blood volume decreases due to plasma decreasing. Plasma decreases due to blood needing to flow to skin to remove heat which it does in the form of sweat.
A decreased blood volume has negative impact on performance due to blood becoming more viscous which makes it more difficult to flow through blood vessels, which decreases the bodies ability to transport oxygen to the working muscles.
Factors that affect blood volume
- exercise intensity
- environmental factors (temperature)
- level of hydration
Muscular Acute Responses
- Increased Motor unit recruitment
- Decreased energy substrate stores
- increased muscle temperature
- Increase oxygen uptake and consumption (VO2)
- Increased metabolic by-products
Increased Motor unit and muscle fibre recruitment
Motor unit= motor neurons and the muscle fibres they control.
Central Nervous System uses motor units to ‘talk’ to the muscles.
Depending on the required strength and speed of contraction the number of motor units that are requited are adjusted.
Motor unit recruitment (All or nothing principle)
‘All or nothing principle’ occurs in a motor unit and tells us that the muscle fibres will contract fully or not at all (dependent on whether electrical impulse threshold for motor unit has been reached)
Types of muscle fibres
- Smaller slow twitch fibres (aerobic, slow events)
- fast oxidative glycolytic fibres (explosive anaerobic movements [ATP-PC]
- Larger fast glycolytic fibres
Increased Muscle temperature
When exercise commences, there is an increase in the rate of metabolism required to produce ATP aerobically in the muscles which causes an increase in muscle temperature.
Heat is the by product of the process of converting chemical energy to mechanical energy (movement)
Increased rate of reactions causes increased heat production and increased temperature.
Thermoregulation
to combat the increasing temperature of the muscles, the body stimulates sweat glands in the skin to produce sweat and vasodilate the arterioles supplying blood to the skin so that evaporative cooling occurs and the blood cools down.
Increased oxygen uptake (VO2)
VO2 is Volume of oxygen that is taken up and used by the muscles increases as exercise intensity increases.
It will continue to increase until VO2 max is reached.
It is a direct result of:
- increase in cardiac output
- and increase in a-vo2 difference
Increased muscle enzyme activity
Enzymes- speed up the rate of reaction
When exercise increases, there is an increase in the activity of:
- ATPase: assist in the breakdown of ATP to release energy for muscular contraction.
- Glycolytic: assist in breakdown of glucose to release energy for ATP replenishment
Decreased energy substrates
Decrease in fuels, such as ATP,PC, glycogen and intramuscular triglyceride used for ATP replenishment and muscular contraction. Level of decrease depends on the intensity and duration of workload.
Increased Metabolic Byproducts (Lactate and Hydrogen ions)
As exercise starts, lactate begins to build up in the muscle due to production of ATP using the anaerobic glycolysis system, Hydrogen ions are formed. When an intensity is reached where lactate production goes above the steady state which it can be removed the athlete will decrease intensity as it increases the pH of the muscles.
(lactate does not cause fatigue, it is just an indicator that there is hydrogen building up in the muscles)
Lactate inflection point
Refers to the final point of lactate steady state
Beyond LIP, lactate is produced faster than it can be oxidised and it will begin to accumulate in the muscles.
LIP will vary between individuals based on level of training (occur later in endurance-trained athletes)
LIP is usually triggered at 85% max HR
