Exercise Physiology: Oxygen, Heat and Fluids Flashcards
What is maximal oxygen uptake?
the level where the amount of oxygen doesn’t increase for the increase in intensity
What is VO2 max dependent on?
cardiac output
What are the three cardiovascular responses to exercise?
increase oxygen supply to skeletal and cardiac muscle, facilitate carbon dioxide and heat removal, maintain MAP
What circulation is decreased in exercise?
splanchnic and renal
What circulation is increased in exercise?
muscle, coronary
What happens to skin circulation in exercise?
it will increase with heavy exercise to facilitate heat loss but with maximal exercise it will decrease in order to maintain perfusion to the brain and muscle
What is the mechanism of vasodilation in skeletal muscle in exercise?
NO, acid, ATP (from RBCs as they desaturate Hb)
What causes post exercise fainting?
stop the muscle pump - stop venous return - sudden reduction in CO - faint
What is functional sympatholysis?
the chemical dilators acting on sympathetic nerve endings to reduce the sympathetic vasoconstrictor effect
Why do athletes have a lower HR at rest?
because they have a higher SV
Why do athletes have a higher SV?
because they have a larger chamber size and expanded blood volume
Why do athletes have a higher VO2 max?
because they have a higher CO due to an increased SV
What is conducted vasodilation?
a mechanism that explains how vasodilation can occur in more proximal vasculature due to electrical signalling from the capillaries that receive the local vasodilator mediators
What is the effect of exercise on systolic and diastolic blood pressure?
systolic blood pressure is a reflection of CO so will increase, diastolic blood pressure is a reflection of peripheral resistance and so will stay relatively stable or fall slightly
What is the effect of exercise on MAP?
it will increase because as the HR increases the heart will spend less time in diastole so MAP will reflect systolic blood pressure
What happens to the baroreflex in exercise?
the baroreceptors are reset so that a high MAP and high HR can be maintained
What is cardiovascular drift?
increased HR and decreased SV with prolonged exercise
What promotes cardiovascular drift?
hyperthermia, dehydration, increased adrenaline, peripheral displacement of blood volume to cutaneous circulation
What is the theory behind why compression garments are used?
decreases peripheral displacement of blood volume to cutaneous circulation so reduce the cardiovascular drift effect
Why does HR increase before you begin exercising?
because there is central control and the motor cortex can influence the CV centre
How is the baroreceptor reset in exercise?
feedback from the muscles communicates to the CNS to inform about the adequacy of the blood supply
What happens to the autonomic nervous system in exercise?
initially parasympathetics (vagus) withdraws and then get an increase in sympathetic activation
What are the microvascular adaptations to training?
increased capillary density and increased capillary recruitment so that the increased CO is better able to be distributed to the muscle
What controls ventilation during exercise?
initially ventilation is proportional to oxygen needs, but with further exercise other stimuli such as acidosis will further increase ventilation rates so that more CO2 can be blown off
How is pulmonary gas exchange influenced by exercise?
Its not - although the transmit time is shorter since gas exchange is perfusion limited not diffusion limited the gas exchange can still be achieved unless there is disease e.g. COPD or asthma
What controls ventilation?
chemoreceptors, stretch receptors in lungs, mechanoreceptors in muscle, pressure receptors, thermoreceptors, hormones, pain receptors, higher centres
What is the of oxygen in the control of ventilation during exercise?
no role
Why is it good for athletes to have a lower ventilation rate?
because it lowers the feeling of discomfort due to breathlessness and it lowers the oxygen cost of breathing
What is the main determinant of VO2 max?
oxygen delivery not oxygen consumption
How can the body lose heat?
conduction, convection, radiation, evaporation
What is the major mechanism of heat loss?
sweat evaporation
What is the major mechanism of heat loss for swimmers?
conduction
What happens to CO with increase in temperature?
increases so that you can increase blood flow to the skin
What is the role of pre cooling?
if lower your body temperature before exercise you will be able to last for longer in the heat because you will go to the same core body temperature
What is the effect of exercise induced dehydration on plasma?
lose plasma volume but not as much compared to interstitial and intracellular volumes
What are the benefits of fluid ingestion on exercise?
increased blood volume, decrease HR, higher SV and CO, lower core temperature, lower plasma sodium, reduced muscle glycogen use, enhanced exercise performance
What happens after exercise?
RAAS activation because you are dehydrated
