Brrrr, it looks cold there! But gorgeous. Utah is one of my favorite states (to look at and visit- need more green and trees and water to live). You guys are so photogenic! Excellent photos! You, your friend, the scenery, the bikes- everything is so perfect. And I think 13mph average speed is _excellent_ with climbs like that! I'd be dying...
Sluggish- probably not enough calories, and also I think it's just normal to be really tired when you're breaking a distance record. Your body doesn't know what to do! Next 50 will probably be a piece of cake.
Nanci