A More Objective Exercise Intensity Scale

Yesterday I proposed a subjective scale to estimate the intensity of physical exercise. Some of you, however, may prefer a more objective or scientific measurement of exercise intensity.

Here is an excerpt from the book Exercise and Sport in Diabetes, 2nd Edition, edited by Dinesh Nagi:
Effort intensity is well correlated with heart rate (HR) in the absence of heart rhythm abnormalities or autonomic neuropathy. One way of defining the intensity of exercise is to state the actual HR as a percentage of the maximal HR. The maximal HR can be calculated or measured during a bicycle or treadmill stress test. Calculated (theoretical) maximal HR for all women or untrained men is 220 minus age. For trained men, it is 205 - 0.5 x age. 
As a trained man, I estimate my maximal heart rate to be approximately 189 beats per minute. "Maximal" heart rate coincides (by definition) with a 10 on our subjective-value scale.

Runner's World Magazine proposes the following percent-of-maximal heart rate values for various kinds of runs:
  • Easy run: 65% to 75%
  • Tempo run: 87% to 92%
  • Interval repeats: 95% to 100%
I will add these values to the training regimen's Legend tab, however I recommend taking this with a significant grain of salt. In my view, running over 90% of your maximum heart rate during a tempo run is too fast.

Meanwhile, hitting your maximum heart rate during interval training is contrary to the approach I'm using in my training regimen. Our objective is to develop fast-twitch muscle fibers using strength training a plyometrics, not during speed work.