Week 9 Flashcards
transport of oxygen
98% of the oxygen in the blood is carried in red blood cells in chemical combination with hemoglobin
arteriovenous oxygen difference (a-v)O2
represents how much oxygen is extracted or consumed by the tissues for each 100ml of the blood perfusing them
stroke volume
the amount of blood pumped by either the left or right ventricle per beat
cardiac output
the amount of blood pumped by either the left or right ventricle of the heart per minute
cardiac output and oxygen transport
When cardiac output increases during exercise, more O2 will be transported to the working muscles.
- expressed by the Fick equation:
VO2 = HR x SV x (a-vO2) diff
VO2 = oxygen uptake or utilization by the tissues in the body
(a-vO2) diff = arterial-mixed venous oxygen difference – amount of O2 extracted at tissue capillary beds
max heart rate=
220-age
when is the heart rate at a given oxygen uptake higher
when the exercise is performed with the arms due to smaller muscle mass, increased intra-thoracic pressure, less effective muscle pump, feedback to control centre
stroke volume during exercise
end diastolic volume minus end systolic volume
diastole: resting phase of the cardiac cycle between heart beats
systole: contraction phase of the cardiac cycle, when the ventricles pump out their stroke volumes
end diastolic volume
the volume of blood in each ventricle at the nd of diastole -120ml
end systolic volume
volume of blood that remains in each ventricle after the ventricles have finished contracting - 50ml
ejection fraction
percentage of EDV ejected with each contraction
stroke volume/end diastolic volume
distribution of blood flow during exercise
at rest 15-20% of systemic blood flow goes to muscles
during maximal exercise 85% of the cardiac output can be diverted to the working skeletal muscles
increased blood flow to working muscles is caused by
increased blood pressure
dilation of arterioles in working muscles due to relaxation of the smooth muscle in the walls of arterioles
constriction of arterioles in the gut area and non working muscles
- due to sympathetic nervous system stimulation
poiseuilles law
restante to flow= fluid viscosity x tube length/ radius of tube ^4
psychological determents of VO2 max
provides an integrated measurement of the capacity of your physiological systems that contribute to
- O2 transport and O2 utilization while maintaining homeostasis
The most important factors that determine VO2 max. in a given person are:
- The ability to ventilate the lungs and oxygenate the blood passing through the lungs
- The ability of the heart to pump blood - cardiac output
- The oxygen carrying capacity of the blood
- The ability of the working muscles to accept a large blood supply
- The ability of muscle fibers to extract oxygen from the capillary blood and use it to produce energy - oxidative enzyme levels, etc.
mode of exercise for VO2 max
In most subjects, the highest VO2max. values obtained during:
– uphill treadmill running
however completive athletes are able to achieve VO2 max values equal to or higher than their treadmill scores while doing their own sport
advantages of bicycle ergometers compared to treadmills
less expensive, portable, don’t require electricity, patient is more stables and body weight is supported- easier to collect psychological data during exercise- heart rate, blood pressure, oxygen uptake , easier to quantify work rate
disadvantages of bicycle ergometers
can’t obtain as high a Vo2 max as on treadmill
cycling is not a common movement for most individuals
reasons for sex difference
Differences in body composition - male has more muscle and less
fat - muscle is metabolically a more active tissue
2. Average male has a 10-14% higher hemoglobin concentration
reasons for decrease with age
- Decrease in maximum heart rate, stroke volume and cardiac output in addition to negative changes in other components of the oxygen uptake and transport systems.
why use a predictive test
- Less expensive and specialized equipment is required. 2. Tests can be submaximal - safety
- Some tests can be administered to large groups
- Less motivation is required from the subject
predictions based on heart rate during exercise
Linear relationship between heart rate and oxygen uptake
in some subjects at heavy work rates VO2 increases relatively more than heart rate.
Similar maximum heart rate for all subjects - standard deviation is approximately ± 10 beats/min. about the average maximum heart rate for people of same age group.
In cases where VO2 is predicted from work rate. a fixed mechanical efficiency is assumed
mechanical efficiency may vary by 6% on a bicycle ergometer.
Day to day variation in heart rate - even under highly standardized conditions (environmental temperature, time of day, diet, drugs, preliminary rest, clothing) the variation in submaximal heart rate is
approximately ± 5 beats/min. with day to day testing at the same work rate.
