I'm 60yo and have read a lot of posts here about calories, hydration & electrolytes and read a couple of books about ld riding (John Hughes', included) and thought I had this all figured out (successfully ridden 200-600k brevets the past 3 years). However, I had problems (weakness and elevated hr) with what I think was dehydration and/or electrolyte loss on my ride last Saturday: 85 mile ride (mixed hills & flat), 78-85 degrees F, high humidity (my southern friend says it's like Louisiana). Consuming Powerade, Spiz, & h2o, drinking every 20 minutes. Average hourly consumption: 27oz fluid, 331 calories, 428mg Na, 322mg K. I've read that the usual assimilation of fluid is no more than 28oz/hr, so I hesitate to go much above this, but should I be stopping to drink more often (I usually don't stop for more than 5 minutes to swap bottles & br break)? Should I up the electrolytes with a couple of capsules? Any insights would be appreciated. Thanks.