Why HR-based training is out-of-date

"My heart is a muscle and it pumps blood
Like a big old black steam train
My veins are the tracks
And the city is my brain"
Cruel Sea - "Black Stick"

It's obvious to say that your heart is an important organ. Like the song goes...at a basic level, it's simply a muscle that pumps blood by contracting and relaxing non-stop, speeding up and slowing down in response to your body's demands for energy (and oxygen). When you consider that, unlike skeletal muscle, your heart doesn't get any rest period it's an amazing little machine that no engineering can yet replicate.

Of course, as an athlete the role of your heart is crucial to your performance. The more blood your heart can pump the greater the supply of oxygen and nutrients to your muscles and the greater your capability. Research has shown a link between the level of effort and HR, with HR ranges equating to different training zones that bring about a training response. To that end, HR monitors (HRMs) have become prevalent amongst athletes wishing to optimise their training and improve their performance. I know because I've worn an HR strap around my chest for more hours than I can count, and established and understood training zones to improve my own performance.

But now I believe that HR-based training is out-of-date. That is, adjusting your work effort in response to what your HR is in order to achieve a training (or racing) outcome is out-of-date. It seems blasphemous to say that, but I'll stand behind that statement and explain why, and what is a better way.

In what might seem like a contradiction, however, using an HRM is still a valuable tool in endurance sports. The key is how you use the tool over time.

Remember that your heart beats in order to meet the demands you place on your body. It's reactive. The things your brain gets your body to do - consciously or subconsciously - is the stimulus. Your HR lags behind the stimulus, and is effected by numerous other things...like temperature, arousal, fatigue, hydration, and so on. Lab tests are done in a controlled environment, whereas you live and exercise in the real world.

To use an analogy, think of a car with the tachometer (rev counter) being a direct measure of the stimulus you exert through the accelerator. In that case, the speedo is a response which takes into account which gear you're in, whether you're driving up or down a hill, and so on. The fuel tanks empties and the engine wears based on the work the engine is doing, not necessarily on the speed you're going at.

So applying that back to exercise and sports performance, relying on your HR to dictate your actual work rate is subject to too many flaws to be reliable. There's a joke that says "an athlete was on track for a PB until their HRM told them to slow down!!". You should be dictating your work rate via the stimulus, that is, the amount of effort you exert through your muscles. I'll explain this more in a moment.

Having said that, monitoring your HR as a measure of how your heart is responding to the circumstances does provide valuable feedback on how your body is going. The key point there is that it's feedback - information on the output of your performance. Over time, and with experience in monitoring how your body responds under various conditions, your HR is one of a number of very valuable feedback streams on how your body is responding...which in turn may influence how you dictate the input / stimulus.

So how and why do you dictate the input / stimulus? Most endurance sports are measured in a very black and white way - time, which equates to speed over the set distance. There's no results list for what your HR was. And for each person there's a direct relationship between the input work rate and the outcome performance. To an extent it's a mathematical equation. If you can maintain a defined work rate then you will achieve a particular time performance.

These days there are ways of measuring input work rate which are far more relevant, usable and helpful to achieving performance than HR ever was. Here they are:

Relative Perceived Exertion (RPE) - Although it's 100% subjective to each person, those who can master RPE in any circumstance have a built-in input gauge for dictating their input work rate. The Borg scale of Relative Perceived Exertion (RPE) is a commonly referred to scale.

Bike Power Meters - In my opinion, simply the best training (and racing) tool for bikes ever invented. Measuring work in terms of watts, there's a range of terms, measures and zones which are defined to dictate the input stimulus you apply to the pedals. There's a range of power meters available which measure bike watts.

Swimming and Running Pace - When used in flat and calm conditions, pace is directly equivalent to bike wattage. That is, the effort you use to swim or run at a particular pace relates directly to a work rate with the same measures, terms and zones as for bike wattage. GPS or footpod watches are the tools for measuring running pace, and the lap clock beside the pool is the tool for swimming.

How you use these tools and methods is the subject of many articles and books, along with defining baseline measures to give the watts and pace context. Once you are familiar with the concept of training based on managing input work rate then a new world will open up to you in terms of how you plan and - importantly - execute your training and racing. For people used to HR-based training it's a paradigm shift, but once you do you won't look back.