I haven't done an Ironman (yet!), but I have done a marathon. During my training for that last summer, I got that same sensation on almost all my long runs. I also would get chills at the same time, even though it was very hot out. I did some research and decided it was due to a combination of dehydration and electrolyte imbalance, in particular sodium. I'm a heavy sweater and I was only using Gatorade. I also found I wasn't taking in enough liquid. I switched to E-Load with some sodium caps dissolved in it to get it to the appropriate level for the heat of the day and starting drinking more. Once I started doing that, I was fine. I'm not sure if your situation is the same, but I hope this helps.

Dawn

Same thing happened to me during my first IM in Penticton in 1999. Everyone told me it was due to dehydration. I had a bit of stomach flu leading up to the race and was probably not as hydrated as I should have been prior to the start and even though I drank a lot during the race I was reduced to a shuffle by 10k into the run with tingly fingers and super heavy arms. I just slowed down (like I had any choice?) and made sure I drank a ton of gatorade at all the remaining aid stations.

I was paging through "Swim, Bike, Run" last night and happened to notice a chart in which the author claims that this sensation is caused when the body has lost ** 6% ** of its weight due to dehydration.

Youch, that's a lot!

matt

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"When I cleaned up my diction, I had nothing left to say" -- Van Morrison

Wow, I had the same experience at IM WI this year too. Except I pretty much went numb from the waist up at mile 16. It got better after a little walking at mile 19, then it hit hard again 1 mile from the finish. I spent about 45 minutes in the medical tent after the race and the docs said it was probably due to a calcium imbalance and not dehydration as I had only lost 1 pound from my pre-race (Thursday) weight. I sure didn't think I was dehydrated but who knows. This is just my experience and probably doesn't help you too much.

Some people have told me they get swollen hands on long runs from blood and fluids pooling in them. Think that could be a factor?

Matt,

IMWI was my first IM, and I ran into the same problem around mile 24. I got to the run after 7:19 (on pace for my 11:20 goal), was low on calories, ran + ran/walked the first couple miles, then dropped to a full walk. I drank plenty of water on the bike, add a bottle or two of gatorade, and a couple salt tabs and food. On the run, I took water and gatoraide at all aid stations and occasionally coke too. Add more salt tabs and GU during the run.

My hands and arms started tingling in mile 23, and moved up to include my face. I had the very beginning of sore legs muscles. Otherwise, I was walking strong, stomach was fine, fully alert mentally. I got to the aid station in mile 24 (Spring St) and decided to take care of myself to ensure a finish.

I put down 10-15 cups of chicken broth, a couple of coke, gatoraid and/or water. It took about 1/2 hour for the tingling to fade, another 1/2 hour the the now light-headed-ness to go away. With a 1:45 mile 24 split, I walked off to the finish line, and was able to run the last few hundred yards.

It was probably a combination of dehydration and electrolytes. I pee'd in T1 (1:15), not again until T2 (7:20), and next at 11:00+.

Joe