Interesting. I've been a runner for over a decade and run 50+ miles/week. I experience light-headedness going from sitting to standing a few times a week.
I bicycle 150 miles a week mostly on steep mountain roads. I seldom faint, but hopping out of bed to go take care of chores in the morning usually results in brief loss of balance and eyesight as my head loses blood pressure for a few seconds.
Sometimes I have to sit down in the bedroom door frame so that I don't faint and collapse. Once I'm up though, my body is full of vigor.
Sometimes I have to sit down in the bedroom door frame so that I don't faint and collapse. Once I'm up though, my body is full of vigor.