On pages 60-61 of the Super Slow Technical Manual I criticized the excessive importance placed on heart-rate measurement. For the benefit of readers without access to that book, I excerpt it (with minor editing):
Authorities differ on the required degree of heart-rate elevation and sustenance for optimum benefit and safety. Heart-rate charts are commonly posted in fitness centers to gauge age and percentage of maximum heart rate. These charts indicate target heart rate. Target rate represents a statistical bell curve. This bell curve represents data points collected by researchers from treadmill and ergometry studies using VO2Max measuring machines and EKG monitoring devices. The target rate or range assumes that the measuring machines are accurate, that the measuring devices were appropriate for measuring what was sought to be measured, that the measurements were performed competently, and that the statistics were honestly calculated and appropriately represented.
I have witnessed the use of these tools and procedures enough to know that it is mostly guesswork. Additionally, it is a tremendous stretch of faith to expect an individual to accurately measure his heart rate during movement, to confidently know his maximum heart rate based on age, and to apply it to a chart representing a statistical bell curve (ostensibly representing thousands of subjects) with the further assumption that he is within the first standard deviation. (This is usually the only deviation depicted by the range on such a chart. It accounts for only ~68% of the individuals in a sample. What about the other 32%?) In other words, the chart assumes that each individual is not at the extreme high or low end of the bell curve. You can appreciate that this simply-charted heart-rate guide is a mess of assumptions built on assumptions.
Some texts and authorities go so far as to assess or define exercise intensity by heart-rate magnitude. Since heart rate may rise or fall without respect to exercise intensity, heart rate does not suffice for this indication. These events do not qualify as factors to determine the qualifications for The First Definition of Exercise (Chapter 15).
In addition to what I stated here, measurement during exercise possesses
much the same limitations and problems encountered with blood pressure.
I am acquainted with several types of pulse monitors. During the Osteoporosis Project,
Arthur Jones supervised measurement of my pulse during a hard set of leg press. Used were
five different devices or methods:
• A $20,000 Quinton Analyzer
• A chest-halter-type digital monitor
• An ear-clip-type digital monitor
• A digital monitor attached to the distal end of my index finger
• A reliable and experienced nurse manually monitoring my carotid pulse.
The result: 5 wildly different readings. Since we possessed greater confidence in our
nurse's manual reading, Arthur summed the situation with: "The body was testing the
measuring devices."
A couple of years ago I chuckled to myself when I read a newspaper article entitled,
"Heart Rate Monitors Might Not Be Accurate." What a revelation that some
exercise physiologists are just now beginning to notice this! Don't hold your breath for
the Target Heart Rate charts to be corrected for these errors — assuming such
correction would be meaningful. Also note that all monitoring and motivational aids used
in aerobic exercise equipment today is based on the same worthless data.