PBL 6 - physiological response to exercise Flashcards
what is exercise?
any activity requiring physical effort — requires work my muscles — requires chemicals
what is metabolic rate?
amount of energy liberated per unit time
what happens to metabolic rate during exercise?
- may increase up to 20x basal metabolic rate
- ie. increased demand of fuel and O2 for muscles
what must be tightly regulated?
temp and pH — requires cardio respiratory response
what 3 things does exercise cause?
- increase in blood temp
- increase in O2 demand by skeletal muscles
- increase in metabolic rate
how do muscles respire at the onset of exercise?
anaerobically as oxygen demand is not met
when is a steady state reached during exercise?
once the CO supply has increased to supply necessary O2
what happens at the end of exercise?
ventilation decreases gradually until the O2 debt has been paid off
how is lactic acid removed?
by converting it to glycogen (80%) or by metabolising it to CO2 and water (20%)
what stimulates the removal of lactic acid and how long does it take?
stimulated by increase in protons in the blood and may take up to 90 minutes
what is EPOC?
excess post-exercise oxygen consumption
what is workload proportional to?
the energy produced which is proportional to the oxygen consumption
what must happen to ventilation to accommodate the increased workload?
ventilation must increase
what happens to tidal volume and resp frequency in low intensity exercise?
increase proportionally
what happens to tidal volume and resp frequency in high intensity exercise?
tidal volume plateaus and resp frequency increases to increase ventilation
what is tidal volume limited by?
physical size of the lungs and the strength of the accessory muscles of ventilation
roughly what is resting ventilation? (L/min)
about 5-6 L/min
what must Hb be in order to supply sufficient oxygen to muscles?
fully saturated
what happens to pulmonary capillaries in order to increase blood flow?
increased blood flow is achieved by the recruitment and distension of pulmonary capillaries especially in the upper parts of the lung which are usually less well perfused
why might there be a drop in pO2 in elite athletes at higher work rates?
due to diffusion limitation because the blood flow increases through the pulmonary capillaries so there is less time for diffusion to occur
why is the diffusing capacity higher in trained athletes?
because the physiological dead space is reduced
what does physiological dead space drop from and to?
about 33% to 15%
what is the effect of PO2 dropping in pulmonary capillaries and what does it drop from and to?
40mmHg —> 25mmHg so alveolar-capillary gradient increases
why does PO2 in pulmonary capillaries drop?
because O2 is used up during exercise