Ok here goes. My RHR is 63. My GP told me it was a water volume issue . SSSSSo I have been drinking a minimum of half a gallon after my rides. Still dizzy when I get up! Noticed some swelling at the ankles after a long day on my feet at work and when I finish my rides. Like i mentioned earlier in a post, I elevated my legs for about 20 min. and was much better. Since my resting rate is pretty low and the kind of shape I think we are in. Figured the blood was pooling in my legs and when I get up the heart does not respond quick enough and bam, dizzy for a few seconds. To the point some times I have to hold on to something for fear of falling. Figured if I can keep the blood from pooling in my legs things might get better, thus the leg elevation tech. Taking a step further, my wife would wear compression socks at work for leg support and to prevent the spider and varicose veins. I borrowed the socks from her and wore them to work for a couple day and the swelling went away and my legs felt good. I noticed pro basketball player using them too. After todays ride I put them on . I actually took them with me to the trail head cause I was gonna put them on right after I finished but forgot. Any way no dizziness ofter todays ride! I am jazzed. Will update after a couple more rides. Give it a try. I would have wore them on the ride but thought it would be a bit warm.
Good luck.