thanks Jesse. yesterday I did a 3hr mountain run at altitude in moderate heat. I drank 3 litres with no problem. it was not crazy hot so that was probably enough. 1.5L/hour if I am really sweating. 30k race this coming weekend at Jackson Hole. forecast calls for 90 degrees in the valley, a little cooler up high…I raced the same race last year and it feels hot. I should be able to tolerate 1.5L/hour of water no problem( 2 500ml soft flasks in the vest and chug an extra one at each aid station). so regarding sodium for the race, if 500mg is the minimum, is it better to take a little extra sodium? or be conservative ? eg 500mg vs 750mg per hour? thanks