People often become lightheaded at the end of very severe ex

People often become lightheaded at the end of very severe exercise in the upright posture (e.g. cross country skiing). Is this most likely due to:

i. Too rapid of a decrease in HR

ii. A failure of venous return to maintain EDV

iii. A rapid increase in SBP

iv. A sudden decrease in SVR

Solution

iii. A rapid increase in SBP

Reason - Increase in oxygen demand by the muscle which increase the rate of hearbeat i.e increase in HR. this increase heartbeat exerts more force so that more blood come out. this cause increase insystolic blood pressure.