• Visual example of heart rate lagging power in a training plan

    (Click on the image to make it larger)

    In my training plans I ask triathletes and cyclists using heart rate as their training monitor to begin an interval with a lower, controlled effort and allow heart rate to climb to the range specified in the plan. The reason I request that approach is that heart rate lags power and many times I'm interested in a constant power output; whether the athlete is actually training with a power meter or not.

    This week I asked one of my athletes to do 60-second power repeats. He executed the workout perfectly. His TrainingPeaks chart (without warm-up and cool down data) shows that he held the assigned power of around 250 watts for 60 seconds and then kept his partial recovery power (Zone 2) between 112 and 151 watts.

    The interval is just long enough so you can see heart rate response. What I want you to notice:

    • On the first interval a heart rate response of 145 occurs after the interval has been completed - heart rate response lag.
    • Peak heart rate response occurs after the power effort is over on all intervals and on the last interval peak heart rate response climbed to 152 - heart rate drift upward.
    • Power over each 60-second interval remained relatively constant – exactly what I wanted.

    Key takeaways:

    1. On any interval, heart rate lags effort (power) to some degree. If your training goal is to build the ability to hold a steady power output for a given amount of time, a heart rate monitor is less helpful for efforts of 60 seconds or less. You can still do the workout without a power meter, but you will need to control your effort so that power doesn't fade during the workout.
    2. For longer intervals (3 minutes or more) working on lactate threshold, aim to begin the interval with heart rate on the low side and allow it to climb throughout the interval, keeping it within the training zone.


    In a future blog I'll post longer intervals working on threshold so you can have a look at heart rate and power response for that type of workout.

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