It's totally illogical but I've been convinced that the heat will hit on marathon day, giving us NO time to acclimate. And I do NOT do well in heat (heat = > 65 degrees). So, I've planned to wear a white singlet to stay cool, visor to block the sun, 70 SPF sunscreen to protect the skin, etc.
The actual prediction? 60 degrees and rain. Sounds fine to me - or - better than heat anyway. This, I can deal with. I KNOW rain, I know 60 degrees, though even that will feel quite warm once I get going. I don't want a downpour, but a few sprinkles will be fine.
So before this forecast came out, I was doing some reading on the Furman Institute of Running website. They have a great download on HEAT & HUMIDITY. I thought I'd share a few interesting tidbits as I know it will be warming up eventually around here and it's already really DAMN hot in other places. There is much more detail in their presentation so if you're interested, I recommend checking it out.
Consider the effects of heat on your body:
- Blood flow increases at skin surface, taking blood flow away from your working muscles
- You experience a decrease in blood volume
- Your heart rate and body temperature gradually increase
- Oxygen and glycogen/energy consumption increases
- All this TIRES YOU OUT
When planning for a race or run, consider both the heat and humidity. The Furman guys give this rule of thumb: If temperature + humidity > 150, be careful! Personally, I think an index of 120 would be good but they're the experts.
What to do when exercising in heat & humidity:
- Drink according to a schedule, do not use thirst as your guide, and start drinking early
- Start getting adequately hydrated 24 hours BEFORE your run
- Drink 0.5 liter about 2 hours before your run (~16 oz.)
- Add carbohydrates to water if exercising > 1 hr
- Consume 500-700 mg sodium per liter of water if exercising > 1 hr
- Drink COLD water to help cool your body and increase the absorption rate of the water