Heart Rate

A simplified chart of heart rate against exercise intensity showing Maximum Heart Rate, Heart Rate Reserve, Resting Heart Rate, Orthostatic Heart Rate, and Heart Rate Deflection.

As exercise intensity increases the heart beats faster, and it's relatively easy to measure heart rate while exercising. This makes heart rate a simple way of evaluating exercise intensity, but you need to understand a couple of common issues to use it effectively.

• Exercise heart rate should be evaluated as a percentage of Heart Rate Reserve. However, you need to do an individual test to determine Maximum Heart Rate. Never use a formula to predict Maximum Heart Rate, as these formulas are useless. If you do a Maximum Heart Rate test, then you can calculate your Heart Rate Reserve, which can be used to estimate exercise intensity.
• A second significant problem with Heart Rate Training is that the relationship between Heart Rate and exercise intensity often changes during prolonged exercise, a phenomenon known as Heart Rate Drift.

The Heart Rate to Effort Relationship

There are several aspects to the relationship between heart rate and effort (power output.)

• Resting Heart Rate (HR_rest) is how fast your heart beats when you are not expending any energy beyond simply being alive. There's also "Zero Power Heart Rate" which is when you're standing or sitting on a bike without any other exertion.
• Orthostatic Heart Rate (HR_orth) is the heart rate when standing, and is typically 10-15 BPM higher than HR_rest. I think of this as "Zero Power Heart Rate." The difference from resting is part of the Orthostatic Heart Rate Test.
• Heart Rate Deflection. Heart rate is generally considered to be linear with effort (power output) up to about 80% of Maximum Heart Rate, and this deflection is often used to estimate Lactate Threshold.
• Maximum Heart Rate (HR_max) is the fastest rate the heart is capable of beating and it must be tested as it cannot be calculated.
• Heart Rate Reserve is the difference between HR_max and HR_rest, thought I believe that HR_orth should be used instead of HR_rest. It's a better measure of intensity than %HR_max.