Hydration/salt levels can always be a factor, and the doctors will likely never tell you this because they have little or no experience with age groupers that return to endurance sports after major heart issues. First, as you suspect, it's not likely prostate or bladder, you are actually dumping a full load of urine and it filled up your bladder suddenly. It is likely one, or both, of the following are in play if you have had recent heart trauma (MI, stent, bypass, AFib/VFib, cardioversion, ablasion, etc.). 1) A heart may have returned to full function and be safe to race, but the heart can become hyper vigilant to release hormones intended to reduce stress on the heart. These hormones act as a natural fast acting and effective diuretic. You may want to try to stay under the distances and efforts where the hormones get released and slowly ramp up until the heart more fully recovers. Carefully managed, it should improve over a year or two. 2) The other cause that may act alone, or be contributing to (1), is heart medications that are not technically diuretics often (in particular the generic versions) have ingredients that unofficially increase their effectiveness by acting as an off label diuretic when the body is under stress. Typically this is calcium channel blockers like generic Norvasc (the name brand version – which is supposed to be the same as the generic – does not cause the sudden onset of urination). Research your meds to see if any have even mild diuretic effect reported in use even if that is not a main vector for effectiveness. They many not be a diuretic in normal use, but can act as such when racing. Medscape has a medications side effects App that has all this information. Finally, even if you haven't had heart trauma, chronic untreated severe obstructive sleep apnea can cause the same effects, particularly if on these meds. If you are not under the care of a cardiologist and this is happening to you, go see a cardiologist ASAP and definitely before your next race. This is not intended as medical advice.

Is this comment for me or the OP... kinda scaring me lol

I had to go back to the op. I think there was a reference to triple bypass. But I believe the op meant a bike race called triple bypass in Colorado.

Very informative post though. Sounds like you know your stuff.

Might as well combine two recent threads... (for efficiency's sake):

Why to I pee so much while failing to get a boner?

I did mean the bike race ;-)

Performance doesn't drop when this happens. No symptoms of at all. No cramps etc...

There is a lot of good information here. Let me add this. If you are 57 and a male, there is a possibility that you have an enlarged prostate (much larger likelihood as you get older). If nothing else works and/or you are passing blood in your urine, see your PCP and possibly request a reference to a urologist. I am 72 and have had your symptoms for years and finally had surgery to remove much of my prostate last January. Before that, I was passing blood after every run (and having urinary difficulties, including your symptoms). Examination showed, among other things, that I had a badly scarred bladder, apparently from the prostate bouncing against it whenever I ran.