Updated: Jan 7, 2021
You know from our recent posts about aerobic endurance training (“How to Adjust Your Training Around the Corona Virus” and “I Walked Today” and “Is The Corona Virus the Best Thing to Happen to Your Triathlon Season?”) that building the aerobic engine first is important to setting yourself up to run faster or ride faster later this year. Now that many of you have cycled back to a base training phase for at least a few weeks, you should be seeing progressive improvements in your base phase. Let’s talk about the two metrics you can use to see how you are progressing.
Note: You will need to use a GPS device, an accurate heart rate monitor (chest strap or arm band), and preferably a power meter for the bike.
Aerobic Efficiency Factor (EF) is a metric that is a good measure of your aerobic fitness. For a given workout, it is equal to your normalized pace or normalized power (NP) divided by average heart rate (HRavg)
EF = NP / HRavg.
As your basic aerobic fitness increases, you should see your EF value consistently increase over time in aerobic workouts (workouts in Zone 1 - Zone 2). If it is decreasing or staying the same over the course of a couple weeks in aerobic workouts—or aerobic sections of workouts—in Z1-Z2, you need to further examine and potentially modify your training. The goal is to have a base phase that is effective.
Cardiac Drift, also called Decoupling (Pa:HR or Pw:HR) is a measure of aerobic economy on a run or ride. It is equal to the ratio of pace to heart rate, or power output to heart rate. The idea is that if you ride or run at the EXACT same aerobic (Z1/Z2) pace for an extended period of time, your heart rate should stay level and not increase. Too much rise over time means there is still room to improve your aerobic fitness.
Cardiac Drift = Ratio of (Pace : Heart Rate) or (Power : Heart Rate)
REAL USE OF AEROBIC EFFICIENCY IN TRAINING
HOW TO FIND YOUR AEROBIC EFFICIENCY FACTOR and CARDIAC DRIFT
"Am I getting the aerobic endurance benefits I need from base training?" Here is exactly how to find the answer:
It's easy to find your EF and cardiac drift in TrainingPeaks Premium if you use a GPS unit and a heart rate monitor (HRM) on runs, and a power meter (PM) and HRM on rides.
Get the Chart Tool I created as a helpful visual. Make sure to download to your device and open your own copy.
Go to the detail view of each aerobic zone (HR zone Z1-Z2) run or segments of runs over the past 2-4 weeks and record the EF and Pa:HR values and date of workout in the appropriate columns of the spreadsheet you downloaded.
Repeat in the bike sheet for your rides in HR Z1-Z2 over the past 2-4 weeks, this time using Pw:HR for cardiac drift.
There are a few more calculations involved in Strava to find EF. The spreadsheet I made also has a tab for Strava data.
Get the Chart Tool. Make sure to download the chart to your device and open your own copy.
Go to each run workout over the past 2-4 weeks that were in your HR Z1-2 and find the analysis graph. Record your GAP (graded average pace, same as NP) in the min and sec columns in the spreadsheet.
Record the HRavg for each run in the appropriate column.
One final point that deserves mentioning is that cardiac drift is very common in hot and humid conditions due to overheating and the body's efforts to cool itself. This has two additional applications for athletes that live in a southern environment:
EF and Decoupling data will be slightly more accurate in the winter months. Just MAINTAINING a constant EF throughout the summer might show great aerobic fitness since the heat and humidity will cause a natural cardiac drift.
You can use these numbers, and your heart rate, to adjust training intensities as needed. If a run is supposed to be easy, but your heart rate is quite high because of the weather, you can back off your paces to make sure you don’t create unnecessary fatigue during an aerobic or recovery session. This takes quite a bit of confidence—a driven athlete never wants to go slower—but listening to your heart rate now and keeping intensity low when it needs to be can pay off big time later on!
If you find that you're not progressing as you'd like to be during your base phase, and you’re wondering how you should modify your training, we’d be happy to help with advice and data analysis, or a more thorough training plan. Just reach out to one of our certified triathlon coaches.
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