I went and participated in the walking event recently. But a strange thing happened so I would like to understand it was all about.
So this 12 hours walking event, I was there for 9 hours, where 8 hours were spent on walking while 1 hour was for one short meal break and to get my protein shakes from my car. I walked a distance of 39 laps which should be more than 42km (according to my GPS, one lap is slightly more than 1km).
When I felt like I had enough, while I was queuing up to collect my medal, I felt slightly nausea, my vision blurred and I lost my balance. A kind elderly man supported me and told me to sit down and someone got me some isotonic drinks. After a very short while, I felt that everything was back to normal and I got back on my feet and drove off.
So now, I am wondering, what exactly happened?
I ran out of fuel? I did not exactly had a decent meal before the event started and neither did I brought along anything except for some cookies. Not too sure about the accuracy of my tracking app but it says I walked a distance of 52km and burned up 5074kcal and 2.6litre of fluid. I suspect it somewhere about 46km because I noticed that it lost track of my position twice.
Dehydration? I felt that I did keep myself hydrated as I was took both water and isotonic drinks, periodically. Perhaps not sufficient enough as 2.6litres as I did not felt it was necessary as I was not sweating as much as running.
Fatigue? The event started at 8pm and I walk on and on until 5am with no longer than 10 minutes rest and I only stopped for 3 times or so. I was awake since 10am before it started. All the while I didn't feel tired, just leg muscles are sore and toes are hurting a little bit.
Hey there, firstly congratulations! Its not easy starting that race, let alone finishing it!
Your condition is clearly after effect of over exerting what your energy stores is capable of. You mentioned you didn't have a decent meal, plus the fact that u felt better after after taking in isotonic drinks shows that you are pushing your body over what your energy stores(glycogen) is sufficient for. Hence the nausea. You burned 5k calories, that is more than a marathon itself, did you train for the distance? Eat more prior and work less to store your energy. If everything remains same, an average man who does sports need around 3k calories a day, if you can't supply that to your body on regular days, then 5k is stretching your body too much.