I’ve been amazed just how much water I must sweat out.!!!
Here’s a little story:
Last Autumn I was probably a bit fitter than now, so didn’t take much persuading to go for a day riding in the Lakes with a friend (who’s stupidly fit and 20 years my junior).
I sweat like a pig all day when riding anyway, but this was just constant effort and I was feeling it! Probably not nore than 35 miles but loads of ascent in maybe 6 hours of riding.
I’d weighed myself when I got out of bed before the ride.
I had porridge, juice and coffee; 3 litres of water/energy drink mixed 50/50 in the pack; butties and jellybabies; pint of coke in the pub after; Indian takeaway and a few pints of water for tea; back on the scales again at the end of the day….and I’d lost 5 lbs!!!
Suffered headaches that evening/night and felt decidedly “off-colour”.
I can only put that down to dehydration.
Difficult to get enough water in to replace what’s lost sometimes.
EDIT – I did start to feel similar yesterday night after a 30 miler in the heat but nothing like the same severity, oh and yesterday I put weight on over the day, which is more normal. – EDIT