If you are not really much of a math person, this formula may look a little intimidating at first. The "e" represents what is called the Euler's constant. Because it is a constant, it is always equal to 2.7182 if we round it off to 4 decimal places.
The "t" is the amount of time that a human can run at the calculated intensity. And finally the "I" is the intensity that is expressed as a percentage of a person's maximum oxygen uptake capacity.
So in other words, this formula predicts how long you can run at a given percentage of your maximum oxygen uptake capacity before the body starts to lock up and you are forced to slow down because the muscles will no longer fire properly.
So what does this mean given the fact that in our example we want to run the 5000 meters in 13:17? What is the "drop dead" percentage of maximum oxygen uptake that we can run for this length of time?
Again, we must substitute our known data into our equation. We know the value of "t" already. It is 13.28 minutes. And we know that "e" is equal to 2.7182. We now make the substitutions:
I = 0.2989558 x (2.7182)-0.1932605 x 13.28 + 0.1894393 x (2.7182)-0.012778 x 13.28 + 0.8
I = 0.2989558 x (2.7182)-2.5664994 + 0.1894393 x (2.7182)-0.16969184 + 0.8
I = 0.2989558 x 0.07680394 + 0.1894393 x 0.84392484 + 0.8
I = 0.0229610 + 0.15987253 + 0.8
I = .98 or 98% of maximum oxygen uptake
Now suppose that you have gone to a physiology laboratory or a good sports doctor and it has been determined that you have a maximum oxygen uptake of 83 ml/kg/min. Given your goal of 13.28 minutes, you can only expect to expend for that length of time 81.34 ml/kg/min tops if you want to make it to the finish line in time. (0.98 x 83 = 81.34)
You also learned on the previous page that it would take 78.63 ml/kg/min to run at the velocity that you are trying to achieve. Since 81.34 is larger than 78.63, you know from these predictions that your goal of 13.28 minutes is now achievable. So like the Nike commercial says, "Just Do It!"