How Much is Enough?

News Flash Folks: It’s hot out there.

And it’s not just hot, it’s humid.

The two combined, make running about as pleasant as yard work. It’s simply another chore that has to get done!

But does it really HAVE to be this way?

I got to thinking and doing a little research.

We all KNOW we should slow down when the temperature rises, but by how much?

First, some facts:

  1. Upwards of 70% of the energy produced is released as heat instead of energy for the muscles.
  2. Sweating is the primary mechanism for heat dissipation.
  3. It is the evaporation of this sweat that cools the body (less is more in terms of clothing in the summer).
  4. Humidity decreases the evaporation of perspiration and in turn, inhibits the body’s ability to cool itself adequately (which is why 120F in Arizona is a more comfortable “dry” heat than the 95F” wet” heat of South Mississippi).
  5. Heart rate increases about 10bpm when temperatures are between 75-90F.
  6. Heart rate increases an additional 10bpm when humidity is between 50-90%.
  7. Performance decreases by approximately 20% when temperatures are above 80%.
  8. Runner’s in the summer produce about 1liter water/500kcal burned OR 3.3-4.4 lbs water/hr which is the same as 1/2 gallon of water lost per hour.  HYDRATE! HYDRATE! HYDRATE!

So, how slow is slow?

Check out this chart below. This doesn’t take into account any additional time for “long runs” or recovery work. This is simply the heat and humidity.


Just a few more months and we’ll all be bitching about how freakin’ cold it is….

I can’t wait!!!

Run Happy, My Friends!

2 thoughts on “How Much is Enough?

  1. Yup…trying to justify my slowness. If I can find just cause, then all is right with the world. Soon it will be winter wind velocities. It ges DAMN windy down here on the beach in the winter… where is that wind NOW when I need it most???? 🙂

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