High-performance runners are typically very efficient. One can observe this just by watching them run: there is no apparent wasted energy. They make it look easy.
So what makes an efficient runner, and why does it matter?
It’s All About Oxygen
You can determine your running efficiency in a physiology lab by measuring how much oxygen is used to produce a given submaximal running speed.
Oxygen consumption is a good indicator of how much energy, in the form of fat and carbohydrates, is used to produce a certain run speed.
As oxygen consumption rises, more energy is being burned. A middle-of-the-pack, age-group runner typically requires much more energy to produce the same speed as an elite runner. The age grouper is less efficient, which could be demonstrated in the lab.
Efficiency is a good way of gauging how fit you are, especially aerobically. The problem is that measuring efficiency in a lab is not only inconvenient, it’s also expensive.
Fortunately, there’s another way of measuring efficiency that doesn’t require a lab. You actually do with with common, everyday training technology. In TrainingPeaks, it’s called the Efficiency Factor (EF).
Measuring Running Efficiency: Using Heart Rate and Pace
By measuring your EF for submaximal, aerobic runs, you can gauge your fitness on a daily basis and compare trends over time.
If your EF is improving, you’re becoming more efficient and therefore more aerobically fit. TrainingPeaks automatically does this analysis for you after a run is posted.
All it takes is a GPS watch and a heart rate monitor. The GPS device tells you how fast you’re running—your performance. And, of course, the monitor reports your average heart rate during the run.
While heart rate doesn’t tell you anything about performance, it is a good indicator of effort. Effort is just another way of saying the cost of the run. Knowing both performance and cost allows TrainingPeaks to calculate your efficiency for a run. So with these two devices, and with TrainingPeaks as a post-workout analysis tool, you have your own “lab.”
So how is it that heart rate is an indicator of cost? As the speed of your run increases, more energy is required. Your heart rate rises accordingly to supply oxygen to the working muscles to produce that energy.
The energy you burn and your heart rate during a run follow the same trend. When the energy required to run increases, heart rate also increases.
Efficient runners require less oxygen and a lower heart rate at a given speed.
How the Effieciency Factor Is Calculated
TrainingPeaks calculates EF by dividing your speed of running by your heart rate required to produce that speed.
If the run was done on a flat course or a track, this is a pretty simple process. But if there were hills, the changes in speed must be taken into consideration. That brings us to something TrainingPeaks calls Normalized Graded Pace (NGP).
Your GPS knows when you’re running up or down a hill. It also knows how steep the hill is. Therefore, it can calculate what your speed would have been if you ran on flat terrain.
That adjustment is the NGP for your run. It typicallys show up in the post-run analysis as being faster than your average pace for the run.
Following the workout, and once data is uploaded, TrainingPeaks knows both your NGP and average heart rate. It converts NGP to a Normalized Graded Speed (NGS—yards or meters per minute) and then divides that result by average heart rate. That produces your EF.
Here’s an example to show you what’s going on inside of TrainingPeaks after you’ve uploaded a run. Lets say your NGP was 7 minutes and 30 seconds per mile and your average heart rate was 150.
- NGP = 7.5 min per mile
- NGS = 60 ÷ 7.5
- NGS = 8 mph
- Yards/Minute = 234.7 (1760 yards x 8 ÷ 60)
- Avg HR = 150
- EF = 234.7 ÷ 150
- EF = 1.56
That’s a lot of math, but thankfully TrainingPeaks does all of that for you.
Using EF to Measure Training Progress
By comparing the EF for similar workouts over time, you can gauge how your aerobic fitness is changing. As the EF rises, aerobic fitness is improving. As it falls, aerobic fitness is decreasing.
Of course, the workouts you’re comparing should be similar, meaning the course and terrain were about the same as well as the weather, your effort, and several other elements that typically affect heart rate (caffeine, lifestyle stress, altitude, etc.)
You can also use EF to measure portions of a workout, such as intervals or a long, steady hill you run up frequently. All you have to do on TrainingPeaks is highlight the section of the run you want data on, and your EF along with the other details for that segment will show up.
One of the best workouts for applying the EF concept is a workout I call the aerobic threshold (AeT) run. Warm-up, and then run for a standard duration, such as 30 minutes, on a standard course while keeping your heart rate 28 to 32 bpm below your lactate/anaerobic threshold heart rate. This is roughly your aerobic threshold.
By recording your EF for that workout portion and repeating this workout frequently you will be able to determine your aerobic fitness progress.
Paying close attention to your EF over the course of several weeks is an easy way to measure your fitness improvement with field tests. It’s also much less expensive than going to a physiology lab every time you want to know.
