Acute muscular responses to
exerciseThe mechanisms responsible for the acute responses to exercise in the
muscular systems (Ms).
Exercise occurs when muscles contract and movement occurs
The type of contraction, the force and the speed of contractions are controlled by the CNS
Acute muscular responses
Ms response
s
Increased motor unit & ms fibre recruitmen
t
Increased ms temp
Increased blood flow
to ms
Increased 02 supply and use
Energy substrate depletion
Increased lactate
Acute muscular responses
Increased blood flow to the muscles
We know that during exercise there is a significant increase in the blood flow to working muscles.
Blood is directed away from non-essential organs to the working muscles
Skeletal capillaries vasodilate allowing for the increase in blood flow to:◦ Increase surface area = increased diffusion rate◦ Allow for increased total muscle blood flow◦ Allows for increased blood volume with minimal
increase to blood flow velocity
As a result of the increase in blood flow to theworking muscles, allowing for greater delivery ofoxygen to meet the metabolic demands of exercise
Increased blood flow to the muscles
Increased motor unit and ms fibre recruitment
Motor unit = a motor neuron and the muscle fibres it stimulates
The means by which the CNS talks to the muscles to control muscle contraction
Increased motor unit and ms fibre recruitment
During exercise, the brain recruits more motor units or it can increase the frequency of messages sent to activate the motor unit
So when the body requires more strength/power/force there is an increase in the number of motor units recruited
Increase the frequency of messages will increase the force produced in the muscle
Increased motor unit and ms fibre recruitment
It is important to remember the “all or none law”
That is a motor unit either contracts fully or it does not contract
A contraction that requires maximal force will recruit more motor units than a contraction that doesn’t require as much force
E.g. Compare holding a pen to lifting a full suitcase
Increased motor unit and ms fibre recruitment
Energy Substrate
When we begin exercising the muscle stores of the fuels we use to produce energy will deplete
The following fuels deplete whilst exercising:◦ATP (adenosine triphosphate) ◦PC (phosphocreatine) (can also be called
CP – creatine phosphate)◦Glycogen levels◦Triglyceride
Energy substrate
ATP is the immediate source of energy for all muscles◦ However, ATP is relatively in short supply and
when it is used up, the muscles must then rely on energy substrates to fuel metabolism
Glycogen is used in both anaerobic and aerobic respiration to produce ATP
During exercise, phosphocreatine (PC) donates a phosphate to ADP to resynthesize ATP
Energy substrate
High-intensity sprint events rely more on the stored ATP and PC as a fuel for energy productions
Endurance events use glycogen and fat
Energy substrate
Increase in lactate
When we begin exercising we are working relying on the anaerobic systems (without O2) and as a result large amounts of lactate is released
It is not until 02 consumption = 02 demand that these stops accumulating in the muscles
When O2 consumption increase to meet energy demands, the lactate can then be delivered to sites for removal
Increase in lactate
At this point lactate is produced and removed at the same time
The last point this occurs is the LIP (Lactate inflection point)
After the LIP, the body is unable to clear lactate at the same rate as being produced, so it accumulates, which equals fatigue.
Increase in lactate
Increased body temperature
Heat is a by product of energy production When you begin exercising there is a rapid
increase in energy production, therefore an increase in heat produced = leading to an increase in body temperature
To accommodate these, increase in sweat glands stimulation and the skin produces sweat, which acts to cool the skin
Blood flow to the skin (as discussed) which cools the blood also
Increased body temperature
Increased 02 supply & use
During exercise more 02 is delivered and extracted by the working muscles because of the increased demand
This leads to an increase in A-V02 diff
Increased 02 supply & use
Now that we know everything, please take the time to update the definition sheet we started at the start of that chapter. Write down definition and any other important information you may want to remember (like formulas such as V = RR x TV or Q = SV x HR)
Now
Mechanisms responsible for the acute responses to exercise in the cardiovascular system.
Mechanisms responsible for the acute responses to exercise in the respiratory system.
Mechanisms responsible for the acute responses to exercise in the muscular system.
Key Knowledge
Participate in physical activities to collect and analyse data relating to the range of acute effects that physical activity has on the cardiovascular, respiratory and muscular system of the body.
Key Skills
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