Here is an idea that adjusts pace by effort. A few years ago I wanted to create a metric that measures how efficiently I’m able to travel at a certain speed. Essentially, I wanted to measure my heart-rate adjusted speed and I was really excited when I read Maffetone’s book and he spoke about achieving various paces for a given heart-rate.
What it Means
What I wanted to do was to take the average speed from a work-out and divide it by my average heart-rate in beats per minute. Mathematically, if you simplify the units you get:
Speed / HR = (mi/hr)/ (beats/min) = 60*(mi/min) / (beats/min)
So by taking your speed in miles per hour and dividing it by your heart-rate (in beats per minute) you get something that measures how many miles you are able to travel per heart-beat. If you divided the result by 60 you would get the actual number of miles you traveled per heart-beat.
I’m proposing that the more efficient you are, the more miles you will be able to travel, so in essence this is a measure that corresponds to miles-per-gallon and indeed each heart-stroke conveys with it a certain volume of blood and if you knew what that volume was you could translate this measure into miles per gallon of blood pumped.
I believe that this measure may be useful for comparing exercises of similar effort, but I expect efficiency to decline as intensity increases (just as driving fast drains more gallons per mile). So hard workouts should still be compared to other hard workouts.
Using my Garmin data and aggregating by month leads to an interesting graph that shows that my efficiency has increased dramatically since I started focusing on volume and is currently higher than it has ever been before.
Fuel Economy Declines Linearly During Exercise
I used data from a recent race to find out how fuel economy declines during a race and the results were interesting. The race was fairly flat and I was able to achieve fairly consistent mile-splits. In spite of this, my speed relative to my heart-rate declined linearly over time indicating that my running economy was becoming less efficient.
Why This Is Useful
Another way to measure running economy from a fuel perspective is to measure oxygen consumption, but this is impossible outside of a laboratory. This measure is easier to implement and you can use it to see how your running economy is improving over time even if your training runs aren’t any faster. The measure is very useful and highly suitable for Maffetone-style training.