As we all know in order to get the best out of our training it is important to not only train at the correct intensities and durations but also to ensure that we recover properly between training sessions. Another factor in all this is how do we gauge our training efforts, do we use power meters if we have them, do we use heart rate monitors if we have them or do we just ride on feel as they did in the good old days?
I do not pretend to have the answers to all these questions but I thought a little bit of data might just be of interest to illustrate just how easy it is to get tripped up in the recovery - heart rate - intensity melting pot. To illustrate my point I conducted a small experiment which was designed to guarantee that I completed a training session when I knew I was not recovered and to gather some heart rate data to illustrate my point whilst keeping other factors constant.
What I did was complete two IDENTICAL workouts, each lasting 65 minutes. My power outputs were absolutely identical during both sessions. Identical power outputs for both sessions were ensured by using a VELOtron (RacerMate) running in ergo trainer mode, the trainer controlled the wattages precisely throughout and the wattages during both sessions were identical, both sessions being controlled by the same control file. The session consisted of a lengthy period riding at a steady intensity and every four minutes there was a one minute effort at a substantially higher intensity before the load returned to the steady state, there were ten such efforts during the sessions. Heart rate was recorded throughout both sessions so that comparisons could be made and the data plotted and compared using Golden Cheetah v3.1.
The two sessions were performed on the same day and there was a period of approximately five hours between the two sessions.
Below is the chart showing the cadence, speed and heart rate traces for the two sessions. The pale blue heart rate trace shows the heart rate trace for the second session performed, as you can clearly see the heart rate during the second session was consistently, and unsurprisingly, higher.
The average heart rate for the first session was 136BPM, the average heart rate for the second session was 145BPM. Bear in mind that the power outputs for these two sessions were IDENTICAL, the only variable was my state of recovery. The percentage increase in average heart rate for the two sessions was 6.6%, that doesn’t sound too much, does it really matter?
It does matter if you are using heart rate to set the intensity of your workouts. To illustrate I plotted my heart rate distribution by training zone for these two sessions, the results are shown below:
As you can see the fact that I was less recovered for session two than for session one five hours earlier has changed the apparent training intensity of the workouts in terms of time spent in HR training zones completely. What was, in HR terms, a predominantly endurance (L2) session the first time it was done has become a predominantly tempo (L3) session when performed five hours later, remember THE POWER OUTPUTS WERE IDENTICAL.
The message is, do consider your state of recovery or fatigue when attempting to reach specific workout intensities if those intensities are set by heart rate data, if you do not you could easily end up doing a session which is, in power terms, a lot harder or easier than it was intended to be!