Exercise Physiology Flashcards
what are the two types of exercise
dynamic
static
what is dynamic exercise
- This is the rhythmical movement of joints and contraction and relaxation of muscles – such as swimming, running and cycling
what is static exercise
- Static – maintained contraction for a length of time – weight lifting
what is the energy requirements of the exercising muscle
- At rest skeletal muscle has relatively low metabolic needs but during exercise as the muscles perform work their metabolic requirements increase
- Energy comes in the form of ATP
name the energy sources
- immediate energy system
- anaerobic glycolysis
- aerobic
describe energy sources
Immediate energy system
- fastest supply of ATP (creatine phosphate/phosphocreatine)
- rapid mobilisation of high energy phosphate
- uses no oxygen
anaerobic glycolysis
- can supply ATP when requirements are high
- less efficient at generating ATP
- uses no oxygen
aerobic
- sustained supply of ATP
- uses oxygen
what is creatine phosphate catalysed by in order to release ATP
creatine kinase
how is ATP generated from anaerobic glycolysis
• ATP is generated from glucose via the glycolytic pathway.
describe lactic acid synthesis
- made when excess pyruvate is converted to lactate
- happens by lactate dehydrogenase
- lactic acid build up can cause a drop in the pH and the muscle can begin to fatigue
what is the VO2
the rate of oxygen uptake by skeletal muscle
how can VO2 be determined
- by the Fick equation VO2 = Q x (CaO2-CvO2) – Q is the cardiac output of the heart (blood flow to muscle) – CaO2 is the arterial oxygen content – CvO2 is the venous oxygen content
what is CaO2-CvO2
CaO2 – CvO2) is also known as the arteriovenous oxygen difference.
– Difference between what is going into the capillary bed versus (in terms of arterial oxygen) what is being removed (in terms of venous)
what should the VO2 be at rest
- VO2: 250ml/min (70kg person) (oxygen consumption)
- 3.6 ml O2 consumed/min for each kg of body mass (ml O2/(min x kg).
define the maximal oxygen uptake
VO2 max is the highest peak oxygen uptake that an individual can obtain during dynamic exercise using large muscle groups during a few minutes performed under normal conditions at sea level. – this is when you are performing maximally at a constant rate
what is VO2 max reached
• VO2 max is reached when oxygen consumption remains at steady state despite an increase in workload.
what does the VO2 max reflect
- it reflects the aerobic physical fitness of the individual
- important in determinant of their endurance capacity during prolonged, sub-maximal exercise
what is the VO2 max in
- COPD/advanced heart disease
- mildy active middle aged adults
- elite endurance athletes
- 10-20 ml o2/(minxkg)
- 30-40 ml O2/(min x kg)
- 80-90 ml O2/(min x kg)
what is the anaerobic threshold
• The anaerobic threshold (also known as the lactate threshold) is the point where lactate (lactic acid) begins to accumulate in the bloodstream.
what happens in the anaerobic threshold
• Lactic acid is produced faster than it can be metabolized, the development of metabolic acidosis occurs and exercise endurance is reduced.
how does the anaerobic threshold vary
- The AT measurements vary from person to person, and, within a given individual, sport to sport.
- Untrained individuals have a low AT whilst elite endurance athletes have a high AT.
what are the aims of adjustments of the cardiovascular system that accompany exercise
- Aim of the adjustments during exercise the muscles are actively working and you need to increase oxygen delivery to these muscles
- As well as remove carbon dioxide
what are the two major changes in the cardiovascular system as a result of increased exercise
- Rise in cardiac output – through increases in SV and HR
2. Redistribution of larger proportion of cardiac output to the active muscles
how does a rise in cardiac output happen when you start exercise
- Heart rate is kept low by the action of the parasympathetic nervous system (vagus nerve)
- Partial vasoconstriction of blood vessels by activity of sympathetic nerves.
- As exercise begins there is reduced activity of parasympathetic and increased activity of sympathetic nerves.
- Increased HR and mobilisation of blood from great veins (vasoconstriction)
what are the cardiovascular changes in exercise due to an increase in sympathetic activity
- Increased venous return
- Increased end diastolic volume (EDV) (increased preload)
- According to Starlings law, increased SV
- Sympathetic activity has a positive inotropic response on the heart.
- The increase in HR and SV act to increase cardiac output during exercise.
what increases CO the most in exercise
- In mild exercise small changes in CO are achieved largely by changes in heart rate and stroke volume
- Stroke volume reaches maximum levels at fairly moderate exercise intestate
- Further increases in CO during heavy exercise are achieved via heart rate changes
- During heavy maximal exercise the increase is achieved by heart rate as stroke volume can be limiting
what are the long term changes of exercise
- heart remodelling
what are the ways in which hypertrophy can happen
hypertrophy can either happen via physiologically such as pregnancy or exercise, or pathologically in diseases such as hypertension
what happens to the heart during exercise
- The heart can adapt to sustained increases in blood pressure by increasing muscle mass largely via an increase in cardiac myocytes size (hypertrophy)
describe the difference between the athletes heart and the failing heart
THE ATHLETE’S HEART
• Increased muscle mass
• Normal cardiac function
• Reversible
THE FAILING HEART • Increased muscle mass • Reduced cardiac function • Irreversible • Cell death and fibrosis
describe why athletes have bradycardia
- Volume induced cardiac hypetrophy in atheletes increases resting end diastolic volume (EDV) and SV
- therefore Athletes typically have a slower resting HR (bradycardia) when compared to untrained individuals
Why are cardiac overloading stimuli (e.g. those experienced during exercise) beneficial whilst others are harmful
- could it be because of different signaling pathways
describe the redistribution of CO to active muscles
- At rest 20-25% of the resting cardiac output is distributed to the skeletal muscles at about 1 l/min.
- During maximal exercise about 80-90% of the increased cardiac output goes to the skeletal muscle with a blood flow of about 22 l/min.
what are the two main mechanisms that control redistribution of blood flow
- Systemic regulation
- Local control
how does systemic regulation control the redistribution of blood flow
- At the start of exercise there is an increase in the sympathetic outflow to the heart and systemic resistance vessels.
- Adrenergic receptors (adrenoceptors) play an important role directing blood flow from non-essential organs to skeletal muscle.
- via alpha adrenorecepotrs, beta 1 and 2 adrenoreceptors
what do alpha adrenoreceptors do
• Alpha adrenoreceptors constrict the vessels in the gut and cause vasoconstriction of veins.
what do beta 1 adrenoreceptors do
• Beta 1 adrenoreceptors (found in the heart) act to increase the rate and force of myocardial contraction
what do beta 2 adrenoreceptors do
• Beta 2 adrenoreceptors act to relax smooth muscle and increase ventilation and oxygen uptake and cause vasodilation of blood vessels, especially those supplying skeletal muscle
how is blood flow locally regulated
- Blood flow is strongly determined by local regulatory factors either from the blood vessels themselves (endothelial factors and myogenic mechanisms) or from the surrounding tissues (tissue factors).
name the endothelial/myogenic mechanisms that help control blood flow locally
- Endothelial/myogenic mechanisms: Nitric oxide acts to relax smooth muscle cells and this causes dilation of blood vessels
name the tissue factors mechanism that help control blood flow locally
- Tissue factors: include adenosine and inorganic phosphates, carbon dioxide, hydrogen ions (H+) and potassium ions (K+) released from contracting muscles.
describe how blood flow to the skin changes
– vasodilation at the skin initially during exercise so it increases initially during light exercises and strenuous exercises but decreases during maximal exercise,
- blood flow to the skin is diverted to skeletal muscles in expense to blood flow to the skin, this means you have not got good thermoregulation
how does total peripheral resistance TPR change during exercise
• Total peripheral resistance (TPR) during maximal dynamic exercise drops dramatically – it is approximately one-third of the resting resistance.
how do you work out MAP
• MAP = (CO x TPR) + CVP
if the TPR decreases why is MABP only slightly increased or normal
- Decreases in TPR are offset by increases in CO
* MABP only rises slightly
describe how systolic and diastolic pressure changes
- Increased force of ventricular contraction (increased SV) causes an increase in systolic pressure.
- In dynamic exercise the diastolic pressure remains relatively stable or even decreases.
- Decrease in the TPR can lead to a decrease diastolic pressure.
how does the respiratory system adjust for exercise
- increased pulmonary minute ventilation
- increased oxygen extraction in tissues
how does ventilation change in exercise
- At rest pulmonary ventilation is about 8l/min but in heavy exercise can increase to 100 l/min or more
- Increased in ventilation is achieved via a rise in respiratory rate and tidal volume (increase in minute ventilation)
- At moderate work rates the steady state ventilation is directly proportional to the work done as measured by the oxygen consumption
- However during severe exercise the increase in ventilation is disproportionately large in relation to oxygen uptake (limiting factor
how is ventilation increased in exercise
- achieved by a rise in respiratory rate and tidal volume( due to increase in minute ventilation)
what is the pathway of oxygen uptake from the atmosphere to the mitochondria during exercise
- Uptake of O2 in lungs - pulmonary ventilation
- Delivery of O2 to muscle - blood flow and O2 content
- Extraction of O2 from blood - delivery and PO2 gradient between blood/cell/mitochondria
how does the blood gases change in oxygen
- At high levels of exercise the partial pressure of oxygen in the arterial blood declines slightly
- As the oxygen consumption rises the partial pressure of oxygen in the mixed venous blood also declines
- The partial pressure of carbon dioxide rises
- Overall the arteriovenous difference in oxygen content rises markedly
- The increase in gradient drives oxygen diffusion into the cells
define the term post exercise oxygen consumption
- There is a measurable increase in the rate of oxygen intake/uptake following strenuous activity (excess post-exercise oxygen consumption (EPOC).
describe oxygen consumption during exercise
- Oxygen consumption does not rise immediately to match the energy requirements, it rises progressively over several minutes until it matches a stead state of the needs of the exercising muscles
- As the work continues the oxygen uptake remains at a level that is appropriate to the degree of exercise
- Thus at the beginning of exercise the body builds up on an oxygen deficit
what happens at the end of exercise to oxygen consumption
- At the end of the exercise period the oxygen consumption declines rapidly but may not reach resting levels for up to 60 minutes
- There is a measurable increase in the rate of oxygen intake following strenuous activity (excess post-exercise oxygen consumption (EPOC)) proposed to be necessary to eliminate the “oxygen debt.”
- During the initial phase of oxygen decline ATP and creatine phosphate are resynthesised (via oxidative pathways). Excess lactate is resynthesised into glucose and glycogen.
what is the challenge of matching cardiac output and ventilation to the metabolic demands of exercise
- The primary site for coordination/integration is the brain central controller/command with input from sensors
what are the factors that regulate the cardiovascular response to exercise
- As exercise begins HR increases and force of contraction increases
- Initially changes due to autonomic factors (inhibitor of parasympathetic and increase in sympathetic)
- Changes are through to be due to signals from higher brain levels (central command)
what does central command receive feedback from
- Central command acts to modulate baroreceptor reflex sensitivity. – the set point changes slightly
- Central command also receives feedback from increased activity in afferent nerves from exercising limbs.
what do metabaroreceptors respond to
• Metaboreceptors respond to changes in metabolite concentrations (mainly pH and K+) – these are stimulated by metabolites in the skeletal muscle, these feedback information about what is going on during exercise
what is the major drive fro ventilation
• Chemoreception also contributes. CO2 major driver for ventilation
what do patients with denervated carotid bodies have
• Patients with denervated carotid bodies have slower ventilatory responses compared to normal subjects. Therefore the response of the peripheral chemoreceptors also involved.
what provides extra stimulus to the peripheral chemoreceptors
• Plasma potassium concentrations are elevated during exercise and are thorugh to provide an extra stimulus to the peripheral chemoreceptors
during exercise there is increased neural input from..
• Increased neural input from afferent activity in the joints
