Should We Ditch the heart rate monitor?


220 – age = MHR. Look familiar?

It’s likely that anybody who exercises or has ever exercised will have seen or heard of this formula. It’s the standard formula for calculating the alleged maximum heart rate (MHR) of any given individual. In this post we’re going to delve into why we believe this formula is flawed. We’re also going to discuss whether we believe heart rate should be included in the conversation when it comes to fitness.

Before we begin, we want to state that we’re cognisant that other similar formulas exist, but for the purpose of this post we’re going to address the most widely used formula amongst the general population and most commercial heart rate monitors, which is the one stated above.

“William Haskell first proposed the 220 formula in the ’70s as an attempt to determine how strenuously heart-disease patients could exercise. As scientists typically do, he checked out existing literature (compiled by his mentor, Samuel Fox) and saw that on average the HR maximum was about 200 at age 20 and 180 at age 40 and so on. The population he examined mostly was under 55; some were smokers and/or had heart disease. By plotting a straight line through the data points, he got roughly 220 minus age … Since then, Haskell has said numerous times he never intended his formula to be used in a fitness environment or by trained individuals.”1

Flaw #1

Imagine two individuals, individual A (IA) and individual B (IB)

1. IA is 20 years old, therefore, their maximum heart rate (MHR) is 200 (220 – 20 = 200). At the age of 20 IA begins personal training and takes up long-distance running with the intention of running a marathon at the age of 25

2. IB is also 20 years old, therefore, also has a MHR of 200. IB leads a sedentary lifestyle, smokes a packet of cigarettes daily, and frequently consumes alcohol in excess

According to this formula, both IA and IB at the age of 25 would still have a MHR of 195 (220 – 25 = 195) regardless of any variables such as level of activity and lifestyle

Flaw #2

MHR is a fixed number

Let’s use an ultra-marathon runner as an example. Let’s assume they’re 50 years old, and they set out on a 50km training run with a specified intensity of 55-60%. This would mean they need to keep their heart rate between 94-102 beats per minute (BPM) for the entire run. Even after running for several hours, they’d still be expected to maintain their specified heart rate because their MHR is fixed. Surely, as the run progresses, and after several hours of running the intensity would need to be adjusted to a relative level, but a fixed MHR and pre-determined heart rate range doesn’t allow for this

Let’s use our two individuals from flaw #1, IA and IB. If both were tasked with running 1km at the age of 25 at an intensity of 75-80%, their heart rate would need to be between 146-156 bpm. For IA it may be appropriate, and it may well feel like 75-80% for them. But it’d likely feel much higher than 80% for IB, and it’d likely be much higher than desired intensity for them

These examples demonstrate why MHR as a fixed number is flawed and will likely not lead to the desired/appropriate intensity

Flaw #3

The formula does not factor in modality

A specialist runner could potentially run at an intensity of 90% for one hour. Let’s assume this same individual is a weak swimmer; if they attempt to swim at an intensity of 90% for one hour because they believe they’re aerobically fit, either they’ll stop well short of an hour or be working at much higher than 90% intensity

Similarly, if somebody who could cycle at 80% for hours on end and has done so for the past 20 years suddenly decides to take up running, they will not be able to replicate the 80% intensity for minutes on end let alone hours on end, because it’s a different modality with very different demands on the body

Is there any correlation between heart rate and fitness?

We’ve already shared our definition of fitness which is relevant in terms of context for this question

A lot of people associate a high heart rate with getting fitter and it’s true, when we exercise our heart rate is elevated, but that doesn’t necessarily mean we’re getting fitter

Somebody who drinks copious amounts of caffeine, gives a public speech, or is a drug addict will also experience an elevated heart rate, but that won’t make them fitter

We believe too many people place too much value on heart rate as an indicator of fitness. We advise tracking metrics such as times, distances and loads, and valuing those metrics instead. Our ability to be faster, go further, and lift more over time will result in improved fitness and be a better indicator, in our opinion

How would we know which zone we’re in if we don’t know our heart rate?

Zone training is a popular mainstream approach to exercise. Usually, a zone between 1 – 5 is prescribed to specify a particular intensity

Specifying a zone of intensity based solely on heart rate is not the ideal approach, in our opinion. Firstly, because MHR is based on a flawed formula as mentioned above. Secondly, there’s many variables that influence heart rate such as caffeine, medication, temperature, stress, sleep, exercise history, age, health conditions etc., therefore, specifying an intensity on heart rate alone will likely not result in achieving the desired/appropriate intensity

We often use Rate of Perceived Exertion (RPE) alongside or in the absence of a heart rate monitor. RPE is simply rating how we feel on a scale of 1-10, and it turns out that we’re really good at judging how we feel i.e., level of intensity

In addition to RPE, we can get a good gauge of intensity by our ability to hold a conversation. In zone 2, we could hold a conversation relatively easily, perhaps needing to take an extra breath every now and then. In zone 3, our sentences would be much shorter with frequent extra breaths. In zone 4, we’d maybe be able to string a few words together, but we’d be breathing heavily. In zone 5, we’d barely be able to get any words out

Zones provide a good framework for intensity, and along with RPE would be far more effective than heart rate alone


In real life, we must be able to function without a heart rate monitor. At GF Fitness, we’re training to be better at life. If we’re playing with the children or playing a round of golf, we’re not going to tell the kids sorry we need to stop or pack up on the 9th hole because our heart rate is too high!

We need to know our limits without relying on an arbitrary number on an electronic device

Thank you for reading this post

We truly hope that you found this post valuable. If you have any questions or if you’d like to work with one of our experienced personal trainers, please feel free to contact us


MacKenzie, B. & Roberts, A. (2011) ‘Follow Your Heart Rate?’, CrossFit Journal, October. Available at: (Accessed: 2 January 2021)

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