Spending pennies like you've got a hole in your pocket.

[disrail]

I was on the 12hr this weekend and did 198 miles.  I must have stopped at least 16 times, and I'm sure many riders on the course will remember me for diving in or out of field entrances. I probably would have made 200 miles if i hadn't had those stops from which it takes a while to get rhythm back.

I've had this before. It's linked with a sudden urge, that just comes on and I HAVE to stop. I was fine for the first half of the 24hr, but had this issue in the second half. It also happened on a DIY 300 in March, when my record was 3 stops in 18km. I also had the issue for 2 days off the bike, when being 10 minutes walk from home almost ended in disaster.

It may be an infection thing, but I don't get any pain. I'm 26, so unlikely to be prostate issues, that's for old men AFAIK.

Any ideas of what the issue could be and any preventative measures?

[Salvatore]

I've had this towards the end (about the 500km mark) of a 600km Audax. Someone once told me it's something to do with a lack of sodium, so I often have a bag of ready salted and that seems to do the trick.

Probably an old wives' tale, but seems to work for me. No doubt someone who knows what they are talking about will be along in a minute.

[juliet]

I get this on audaxes (and sometimes other times, but most notably on audaxes), especially on the second day of a long ride.

Might be worth getting a physio referral.  When I had serious off-bike issues a decade or so ago I spent an unpleasant while being sent for investigations by a consultant who couldn't find anything wrong, and eventually was referred to a physio who taught me various muscle-control exercises.  (Kegels/pelvic floor exercises, basically.)  In my case, caffeine is also a trigger, as is alcohol - both are apparently bladder irritants (I think that's what the physio said).  So another option would be to keep an eye on what you're taking in when you have these problems!

Someone once told me it's something to do with a lack of sodium, so I often have a bag of ready salted and that seems to do the trick.

That's interesting - I've speculated about forms of dehydration before & whether water goes through slower, as it were, with a bit of sodium intake.  I shall experiment more thoroughly in future

[hellymedic]

As the others have suggested, sodium may be part of the issue.
Another part is glycogen; each gram of glycogen holds 3-4 grams water to itself. If your glycogen stores start at 400 grams, burning them may liberate about a litre and a half into your circulation, whence it goes through the kidneys next.
Try some kind of food should this problem occur again; experiment with the sweet and the salty...

[alexb]

I too find that unless I keep up a fairly high salt intake when riding, any water I drink just goes straight through me.
I'm another lover of salted snacks, cashew nuts especially, or crisps at a pinch. Apples are also good for some reason (trace levels of minerals perhaps?).

[Biggsy]

It may be an infection thing, but I don't get any pain. I'm 26, so unlikely to be prostate issues, that's for old men AFAIK.

Young men can get an enlarged prostate, though it's unlikely to be cancer.

[geraldc]

I was told by my motorbike instructor that if your kidneys get cold, you need to pee more, which apparently is behind the large market for kidney warmers for bikers

[hellymedic]

I don't think cold kidneys are a likely issue for a 12 hour daytime August time trial, though I agree the British weather can be challenging...

Getting cold anywhere will cause vasoconstriction and diuresis, granted. I just don't think this is the OP's problem.

[Ian H]

I have had frequent urges to pee when knackered beyond the point of return and just limping to the finish. Somewhere I read an explanation that I have since forgotten.

[disrail]

Cheers for the insights.

On all occasions I was drinking quite a bit. I'm not a sweater at all. I played frisbee with a guy who could wring out his jersey after a days play in summer, while mine was perfectly dry.

The most worrying thing is how suddenly it comes on. Sudden pressure, and I have to stop within the minute. No ability to hold it. This happened 3 times in 18km!!

I'll look into pelvic floor exercises, try some cranberry (gotta work) and keep the salts up.

[hellymedic]

It's happened to me, usually towards the end of a long Audax. You are not alone!
If you're not one to sweat (unlike me) maybe you don't need to drink quite so much.

[juliet]

The most worrying thing is how suddenly it comes on. Sudden pressure, and I have to stop within the minute. No ability to hold it. This happened 3 times in 18km!!

This sounds like pelvic floor exercises will help.  (Having said that, I do very much know the feeling of dire urgency!  IME sometimes it's more possible than other times to hold it, & I do quite often find that if I *can* hang on past the "sudden pressure" feeling (clench all relevant muscles for at least 10 seconds, breathe slowly and remain calm as getting anxious makes it worse!), it'll go away again a bit.)