38 - Exercise Physiology Flashcards
What is the difference between dynamic and stable exercise?
Dynamic - rhythmical movement and contraction and relaxation of muscle
Static - maintained for a long length of time e.g lifting
What is the immediate source of energy for muscle function
Creatine phosphate
catalysed by creatine kinase
(uses no oxygen)
What is the non-oxidative source of energy for muscle
Glycotic pathway
Excess pyruvate converted to lactic acid
Lactic acid build up
= Ph drop
What is the oxidative source of energy for muscle
Requires oxygen
- oxygen phosphorylation
What is VO2 at rest
(Volume of oxygen consumed at rest)
250ml/min (70kg person )
How much oxygen is consumed/minute for each kg of body mass
3.6ml O2
VO2 max
maximum oxygen consumption is reached at steady exercise
Reflects the aerobic physical fitness of the individual
Fick equation
VO2 = Q x (CaO2-CvO2)
What does Q, CaO2, CvO2 stand for
Q - cardiac output
CaO2 - arterial oxygen content
CvO2 - venous oxygen content
What is the anaerobic threshold
The point where lactate begins to accumulate in the bloodstream
Lactic acid is being produced faster than it can be metabolised - determines fitness and varies individuals
What does exercise do to increase HR
reduced activity of parasympathetic and increased sympathetic nerves
What does exercise do to increase stroke volume
Increases venous return
Increased EDV - increased SV via starling’s law
Sympathetic activity has positive inotropic response on the heart
How does the heart adapt to sustained increases in blood pressure
Increases muscle mass - hypertrophy ( increase in myocyte size)
Can be physiological (reversible) or pathological (irreversible)
Compare an athletes heart and a failing heart
Athletes heart - increased muscle mass, normal cardiac function, reversible
Failing heart - increased muscle mass, reduced cardiac function, irreversible, cell death and fibrosis
What is the difference between blood flow to skeletal muscle at rest and during exercise
At rest – 20-25%
During exercise – 80-90%
What is the the role of alpha adrenoreceptors in the redistribution of blood flow during exercise
constrict the vessels in the gut and cause vasoconstriction of veins.
What is the the role of beta 1 adrenoreceptors in the redistribution of blood flow during exercise
(found in the heart) act to increase the rate and force of myocardial contraction
What is the the role of beta 2 in the redistribution of blood flow during exercise
act to relax the muscle and increase ventilation and oxygen uptake and cause vasodilation of blood vessels, especially those supplying skeletal muscle
What is the local control of blood flow during exercise
Tissue factors - adenosine and inorganic phosphates, carbon dioxide, hydrogen ions (H+) and potassium ions (K+) released from contracting muscles.
Endothelial mechanisms – NO
What happens to skin blood in moderate exercise
Skin blood flow increases (part of the thermoregulation response)
What happens to skin blood in intense exercise?
vasoconstriction takes over and blood redirected to skeletal muscles at the expense of the cooling action (i.e. temperature will rise).
What are the blood pressure changes during exercise?
MABP only rises slightly
Decreases in TPR are offset by increases in CO
Increased force of ventricular contraction (increased SV) causes an increase in systolic pressure.
In dynamic exercise the diastolic pressure stable or even decreases.
How are the body’s need for oxygen met during exercise
Increased pulmonary minute ventilation
Oxygen extraction in tissues
What is rest pulmonary ventilation and what can it increase to during exercise?
Rest pulmonary ventilation - 8 l/min
Heavy exercise - increase to 100 l/min or more.
At the start of exercise, PV increases and rises till it reaches a steady state appropriate to the work being done
- 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 an increase in ventilation achieved
Rise in respiratory rate and tidal volume
What is the pathway of oxygen from atmosphere to 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)
What happens to the arteriovenous difference in o2 content?
Rises so increases in gradient driving oxygen diffusion
What happens to the PaO2 in the arterioles and venous blood?
Arterial blood - decreases slightly
Venous blood - decreases but paCO2 increases
What happens to the Hb-O2 binding affinity during exercise?
Decreases so oxygen delivery is increased
- increased CO2, increased H+, increased local/tissue temperature
What is excess post-exercise oxygen consumption?
Increase in rate of oxygen intake following strenuous exercise - necessary to eliminate oxygen debt
What does a denervated carotid body do?
Slower ventilatory response than a normal subject
