It's that time of the year when many triathletes are starting to wonder if all of that base training has paid off. How can you know that you've achieved adequate base aerobic fitness and you're ready to start building toward your race peaks?
David Warden at tri-talk posted an excellent podcast on this topic about a year ago and if you haven't listened to the audio or read the transcript, I'd highly recommend it. Here's a little excerpt on how to determine base aerobic preparedness using heart rate and output:
There is a method to determine if you have a sufficient aerobic base, and I want to thank Joe Friel of TrainingBible coaching for providing me with this information.
This test protocol simply compares your power or speed with heart rate over an endurance ride or run. There is some research to indicate that when aerobic endurance improves there is reduced heart rate drift relative to constant power or constant speed. And, of course, the reverse of this is that when heart rate is held steady during extensive endurance training, output may be expected to drift downward.
For example, the next time you download a workout from your training device, you probably have the ability to graph HR and power or speed on the same chart. In a perfect endurance ride, where there were no intervals or significant intensity, just a nice long Zone 2 ride, these two lines would run relatively parallel to each other.
However, you may have noticed that on some of these long rides, your HR tends to drift up even when output remains the same. Or, if you are trying to maintain a Zone 2 effort, you may notice that when you look at the graph that even though HR remained the same, out (power or speed) went slowly down. In those cases, the lines on the graph representing HR and output no longer run parallel, but begin to drift apart.
The parallel relationship between heart rate and output (power or speed) is referred to as “coupling.” When they are no longer parallel in a workout they have “decoupled.” Excessive decoupling would indicate a lack of aerobic endurance fitness.
But how much is excessive? There is an acceptable amount of decoupling that can take place and still indicate a solid aerobic base. A good indication that a base fitness has been met is less than a 5% decoupling over a Zone 2 workout.
