"They declare it a myth but I will continue to manage my hydration."
+1 Dehydration is a process that proceeds along a continuum that begins when you lose your 1st gram of water, either from sweating, urination, respiration, or defeCation(foiling the potty police here). At some point, if fluid loss continues, a person's athletic performance will suffer. Apparently, that point was not reached for the people in their example. I can cite personal experience as an anecdote to the contrary. I ran 4 sub 3 hour road marathons back in the early 80's in mostly cool to moderate conditions, with no apparent effects from dehydration. Fast forward to the mid 90's when I ran 3 trail marathons in very hot conditions that took me 5:15, 4:40, and 4:16 to complete. The 5:20 effort ended with a trip to the emergency ward with heat exhaustion that required a 2 liter infusion of H2O/electrolytes to treat. The 4:40 effort left me very obviously dehydrated but not in dire straits. The 4:16 effort left me tired but in decent shape physiologically. Notice the correlation between elapsed time and dehydration. My point is that fluid loss over time will lead to decreased performance and possibly life threatening heat exhaustion. There has been enough written on the subject that I will not bother collecting a bunch of links to "prove" my point. Google it up for yourself, Eric. Like Greg, I will assiduously manage my hydration, quite simply because I have seen what happens when I do not.