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Power vs. Heart Rate

If Power vs. Heart Rate was a boxing match, Heart Rate wouldn't make it through the first round when it comes to interval training.  Here's why Power is the ultimate metric for interval-based training.

Weaknesses of Heart Rate

  • Heart rate varies based on many external factors
    • Fatigue
    • Sleep
    • Stress
    • Illness
    • Glycogen level
    • Hydration level
    • Temperature
    • Humidity
    • Motivation
    • Caffeine
  • As a result, your heart rate zones can change dramatically from day to day
  • It takes 90-120 seconds for your Heart Rate to respond to a given effort
  • Cardiac Drift:  As you become more fatigued, your HR continues to get higher throughout a workout due to multiple fatiguing factors such as dehydration and muscular fatigue

Strengths of Power

  • FTP is a solid and stationary number.  Some days you may not be able to express high percentages of your FTP, but that does not change the value of your FTP
  • Assuming your equipment is properly calibrated and correctly zeroed, if you aren't living up to your power targets, you know with greater certainty whether fatigue is an issue and can rule out most external factors skewing your data measurement
  • As you get faster, you can quantify the extent of your improvements through recurrent FTP testing

Podcast Discussion

[56:10] Podcast 134:  Power vs. Heart Rate


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