exercise physiology Flashcards
what are the types of exercise?
dynamic
static
define dynamic exercise. give examples
rhythmical movement of joints and contraction and relaxation of muscles. Swimming, running & cycling.
define static exercise. give examples
maintained contraction for a length of time. Weight-lifting
what ATP supply is the immediate energy system? what is its function?
fastest supply of ATP - creatine phosphate (phosphocreatine) function - rapid mobilisation of high energy phosphates. uses no O2
what ATP supply does anaerobic glycolysis provide? what is its function?
can supply ATP when requirements are high
less efficient at making ATP. uses no O2.
what ATP supply does oxidative metabolism provide? what is its function?
- sustained supply of ATP
- function; uses O2
what are the 3 sources of metabolism that support skeletal muscle function?
- Immediate
- Non-oxidative
- Oxidative (aerobic)
where are high concentrations of creatine phosphate found?
in the muscles
what is the function of creatine phosphate?
• Provides a store of high potential phosphate to maintain contraction
what is phosphocreatine broken down to and what catalyses this reaction?
• Phosphocreatine creatine produces ATP
o Catalysed by creatine kinase
how is ATP generated in anaerobic glycolysis?
ATP generated from glucose via the glycolytic pathway – less efficient at making ATP
what causes muscles to fatigue?
- Excess pyruvate lactate
- Lactic acid build-up
- Drop in pH – muscle begins to fatigue
where is energy derived from in sustainable exercise?
aerobic metabolism
need O2
what is VO2?
the rate of O2 uptake by skeletal muscle (amount of O2 consumed)
what equation can determine VO2?
VO2 can be determined by the Fick equation
what is Fick’s equation? define each term
VO2 = Q x (CaO2 – CvO2)
Q – cardiac output of the heart (blood flow to muscle)
CaO2 – arterial oxygen content
CvO2 – venous oxygen content
(CaO2 – CvO2) is also known as the arteriovenous oxygen difference
what is the VO2 in a 70kg person?
250ml/min
how much O2 is consumed/min/kg body mass?
3.6ml/min/kg of body mass
what is VO2 max?
– highest peak O2 uptake obtained during dynamic exercise using large muscle groups during a few mins performed under normal conditions at sea level
when is VO2 reached?
when O2 consumption remains at a steady state even in an increase in workload
what does VO2 show?
Reflects aerobic physical fitness of the individual – important determinant of endurance capacity during prolonged, sub-maximal exercise
what is the anaerobic threshold?
point where lactate begins to accumulate in the bloodstream
how does lactic acid reduce exercise endurance?
Lactic acid produced faster than it can be metabolised metabolic acidosis exercise endurance = reduced
would elite athletes have a high or low anaerobic threshold?
high
what are the 2 major consequences of increased exercise?
- Rise in cardiac output – through increases in SV and HR
* Redistribution of larger proportion of cardiac output to the active muscles
how is HR kept low?
action of the parasympathetic nervous system (vagus nerve)
how are HR and SV increased at the start of exercise?
- As exercise begins, there’s reduced activity of the parasympathetic nerves and increased activity of sympathetic nerves
- Increased HR and mobilisation of blood from great veins (vasoconstriction)
- Increased venous return Increased EDV (increased preload) increased SV
- Sympathetic activity has a positive inotropic response to the heart
define hypertrophy
increase in cardiac myocyte size to increase muscle mass
how can hypertrophy of the heart muscle occur?
physiologically
pathologically
how can physiological hypertrophy occur?
pregnancy or exercise
how are the left ventricles affected for;
- endurance athletes
- strength athletes
- combination athletes?
Endurance athlete – thickening of LV walls LV dilation
Strength athlete mild LV dilation
Combination athlete gross thickening of LV walls LV dilation
how can heart muscle hypertrophy occur pathologically?
Hypertension – thickening of LV walls no dilation in early stages of disease
Dilated cardiomyopathy, heart failure thinning of LV walls significant LV dilation
Hypertrophic cardiomyopathy gross thickening of LV walls no dilation/decrease in LV chamber size
what physiological remodelling occurs in an athlete’s heart? is it reversible?
o Increased muscle mass
o Normal cardiac function
o Reversible
what physiological remodelling occurs in a failing heart? is it reversible?
o Increased muscle mass
o Reduced cardiac function
o Irreversible
o Cell death and fibrosis
how does volume-induced cardiac hypertrophy occur?
increases resting EDV and SV
how does the HR of athletes compare to untrained individuals?
athletes have bradycardia
at rest, what % of resting CO is distributed to the muscles?
20-25%
during maximal exercise, how much of the increased CO goes to the muscle?
80-90%
what mechanisms control redistribution of blood flow?
systemic regulation
local control
how does systemic regulation control distribution of blood flow?
- Start of exercise – increase in sympathetic outflow to the heart and systemic resistance vessels
- Adrenergic receptors play an important role directing blood flow from non-essential organs to skeletal muscle
what do alpha adrenoreceptors do?
constrict vessels in the gut - cause vasoconstriction of veins
what do beta-1 adrenoreceptors in the heart do?
increase rate and force of myocardial contraction
what do beta-2 adrenoreceptors do?
relax smooth muscle and increase ventilation + oxygen uptake and cause vasodilation of blood vessels, esp those supplying skeletal muscle
where do local regulatory factors that control blood flow come from?
blood vessels themselves
surrounding tissue
what local regulatory factors come from the blood vessels?
endothelial factors and myogenic mechanisms e.g. NO relaxes smooth muscle and causes dilation of blood vessels
what local regulatory factors come from the surrounding tissue?
tissue factors. E.g. adenosine and inorganic phosphates, carbon dioxide, hydrogen ions (H+) and potassium ions (K+) released from contracting muscles
how does increasing vasodilator metabolites increase muscle blood flow?
decreases TPR which increases skeletal and cardiac muscle blood flow
how do you calculate MAP?
MAP = (CO x TPR) + CVP
why does MABP rise only slightly in exercise?
decrease in TPR is counteracted by increases in CO
how does systolic pressure change in exercise and why?
increases bc of increase in ventricular contraction force
how does diastolic pressure change in dynamic exercise?
stable/decreass slightly
how is the body’s increased need for O2 met?
met through increased pulmonary minute ventilation and oxygen extraction in tissues
what is the pulmonary ventilation at rest?
8L/min
what is the pulmonary ventilation during heavy exercise?
100L or more
what causes the increase in minute ventilation in exercise?
increase in resp rate
increase in tidal volume
how is O2 taken up into the lungs?
pulmonary ventilation
how is O2 delivered to the muscle?
blood flow and O2 content
how is O2 extracted from the blood?
delivery and Po2 gradient between blood/cell/mitochondria
how do blood gases change during exercise?
- High exercise levels – arterial PaO2 declines slightly
- As O2 consumption rises, PaO2 in the mixed venous blood also declines
- Partial pressure of CO2 rises
- Arteriovenous difference in O2 content rises
- Increase in gradient drives O2 diffusion into cells
why is there reduced affinity of Hb for O2 during exercise?
- Increased CO2
- Increase H+
- Increase in temperature
what effect does reduced affinity of Hb for O2 have on O2 delivery to tissues?
increases O2 delivery to the tissues
define excess post-exercise oxygen comsumption
measurable increase in the rate of oxygen intake/uptake following strenuous activity
how does the body build up an oxygen deficit?
- O2 consumption doesn’t rise immediately – rises over several mins until it matches the needs of the exercising muscles
- As work continues, O2 uptake remains at a level that’s appopriate for exercise levels
why is EPOC needed?
eliminates O2 debt
what is made during the initial phase of O2 decline?
ATP and creatine phosphate are resynthesised via oxidative pathways
• Excess lactate is resynthesised into glucose and glycogen
what causes changes to HR and contraction force occur after autonomic factors?
- Changes bc of signals from central command of the brain
- Central command acts to regulate baroreceptor reflex sensitivity
- CC also gets feedback from increased activity in afferent nerves from exercising limbs
- Metaboreceptors respond to changes in metabolite concentrations (mainly pH + K+)
what mechanisms activate respiratory muscles?
neural mechanisms
what part of the brain causes an increase n ventilation?
initiation of motor activity from premotor area of the cerebral cortex
chemoreceptors also contribute
what is the major driver for ventilation?
CO2
what effect does a denervated carotid body have on patients?
they have slower ventilatory responses
what effect do elevated potassium concentrations have on the body during exercise?
thought to provide an extra stimulus to peripheral chemoreceptors.
