Getting the most from your HRM

Efficient Targeted Heart Rate Training


Why train cardio/HIIT with a HRM? Well 90 % of those who do train will elect a moderately challenging effort range because it makes them feel like they are working hard enough, one thats not too uncomfortable. However this won't achieve a factual body response and hence it's a fail. Using a heart rate monitor with pre calculated training intensity zones will suddenly embarrass previous efforts, leaving only two options; Step up and do better or go home knowing you lost.....

Fitness tracking hardware has exploded. It is forecast that the market will hit $14.9 Billion by 2021. Advancement in technology now gives fitness wearables and trackers the ability to not only record data, but they bring big data and enough “real time” data that can be turned into improving athletic performance or managing overall personal fitness.

The one fitness tracker that is considered to be a serious piece of kit above all others and provides the most benefit to training is a “heart rate monitor” (HRM). In the bid to become fitter and leaner many of you have purchased or are thinking of purchasing a HRM, but are you:


  • Taking full advantage of its features and avoiding some of the basic errors many make when training with a HRM?

  • Using your HRM correctly to get accurate data?

  • Have you considered using your heart rate to assist recovery, sleep, monitor stress and record baseline fitness levels?

  • Setting and adapting your training zones to match you training session goal?

Your Heart Rate

Your heart rate is a metric that is constantly signalling out information to your level of cardiorespiratory fitness and any inducement of stress upon your metabolism from training load, psychological pressures or infection/illness.

A heart rate monitor works by “listening to each beat of the heart” and breaking down that information as live data feeds that it then communicates (via Bluetooth or ANT) to specifically developed software held on a hardware devise like an iPhone or computer. 

We are able to “read” this data by interpreting the physiology of the circulatory system. With every beat of the heart (heart pump) a specific level of blood (stroke volume) is pushed through the circulatory system. The frequency of this contraction of the heart is in fact the heart rate (HR). The amount of blood pumped into the cells of the body every minute comes from the heart rate and stroke volume. (HR x stroke volume)  and this is why we measures heart beats in bpm (beats per minute).


Elite athletes are not the only ones who should be concerned with heart rate


The heart is a muscle, and like all muscles you can make it stronger with exercise. When we place aerobic challenge upon our metabolisms, we trigger an adaption at cellular level that leads to an increased level of VO2 Max (we get fitter). During this adaption process the heart must get stronger as the increased “aerobic exertion” stimuli placed upon it causes the heart to become “stressed” as the demand to feed through more oxygen to the muscle cells becomes greater. The heart responds to this challenge/stress by increasing the rate in which it beats. So the stronger the heart, the more blood per beat you are able to pump, and that’s why the fitter you become the lower your heart rate will be at rest, and because cardiac output is directly proportional to the heart rate, we are able to use an HRM as an effective tool to precisely control training intensity and ensure workout efficiency.

How to use an HRM to achieve accurate data readings


It’s important to highlight here that although current HRM technology is very good, and widely accepted as an “accurate measuring tool” by the majority of medical and fitness professionals, NO HRM IS always 100% perfect or accurate in calculating beats per min (kcal burn etc. is attributed to the software/app used) under all conditions.

In part this should be expected due to the complexity, unpredictability and individuality of each human body, for example a chest or wrist strap may fit one person better than another, and one individual may sweat more than what the manufacturer tested for.

However accuracy also lies in part with the user. Ensuring the HRM is fully charged or has good battery charge, the correct placement and tightness when applying the HRM to the body, and also checking it remains in position during the entire workout all make a difference for accuracy.


The individual needs to be smarter than just the HRM device … to be able to see when those beats per min numbers may not be correct, then pause the workout, re align the HRM and then continue...

It's also important to consider that although your HRM may get an accurate reading, that reading is also subject to the many internal and external factors that can affect your heart rate. Outside temperature, skin/core temperature, dehydration, stress levels , excitement, overtraining, or diet are all variables that can affect your HR. When it's cold expect it much harder for your HR to reach those high targeted HIIT HR zones, my advise lower them. Equally when its very hot expect higher than normal HR readings, this places higher demand upon our metabolisms so use the data to help normalise your body, i.e. get in more fluids and recovery. 

There is no one rule fits all here. Instead get to know your body and how it responds to different conditions by using an HRM frequently, recording the data and analysing the results. 

Resting heart rate - a useful metric for recovery 

There is a lot of emphasis placed on the benefits of how the beat of the heart responds during exercise, but did you know our hearts are whispering messages to us throughout the day ? 

Another big benefit to having and using a HRM is it gives you the ability to measure your heart rate at rest. Now many of the training zones that you will use during exercise will use a formula that includes the heart at rest. However by taking regular RHR measurements there is evidence that we can assess both improvements in baseline fitness and if our body is getting enough recovery or an infection is entering our cellular system. 

Now RHR means "resting heart rate" which is how fast your heart beats per minute (bpm) when you are at complete standstill rest, and this reading is best achieved immediately upon waking up in the morning and taking a 60 second reading whilst laying down in your bed. The lower the number, the fitter you are. The average adult will have a resting heart rate between 60-100 beats per minute, while athletes will have much lower readings in the  40-60 bpm range. 

When my clients begin a training program with me , in most cases I expect to see a lowering of the RHR as one of the metrics that indicate an increase in baseline fitness. Typically clients start in the 70-75 bpm range and after 4 weeks its 50-55 bpm and after 8-12 weeks as low as 45 bpm.

Now once you begin to take regular readings, over time you will establish your baseline RHR. This will be bpm reading closest to your normalised lifestyle, i.e. you are not in the middle of sitting exams or going through a break-up. This metric marker becomes useful because we know under stress our HR alters and this could indicate a sign of overtraining, stress at work or an infection entering your system as the heart is placed under greater demand to begin the "flushing process" As a good marker if you're reading is 7-10 bpm higher than baseline, then I advise further investigation into your personal wellness in the form of BP reading, temperature reading, oxygen saturation, visit to your GP, or if are experiencing fatigue from training then the rise in the RHR metric should prompt you to resist your training plan.

Which HRM is most accurate?


The most accurate HRM will always be the one that's best suited to you, and the one that gains your confidence. As someone who has trained with HRM's for over ten years and tried them all, my advice is always to allow sufficient time to get to "know" your new training partner. The strap position and tightness, type of clothing, temperature, training intensity and exercise type are all factors that can effect a HRM reading. Get to know what works for and against a reading on your HRM, and use trial and error to pick the HRM that best fits you. The cost of a few HRM's in the selection process is nothing compared to cost of a loss of training efficiency. 

At present there are two main types of commercial heart rate monitor (HRM) you can purchase:

Chest Strap

These are worn on the chest with a chest strap that detect the heart pulse via an electrical signal and give “ECG quality R to R interval measurements. These are currently considered the most well developed and are the type most widely used by fitness professionals.

As they do not offer “on-board” memory they must be wirelessly connected to a third party devise such an iPhone (using the CardioGuru app) or computer using either ANT (which is slowly becoming redundant) or, Bluetooth 4.1 low energy that increases smartphone battery life dramatically. All chest straps using Bluetooth 4.1 can sync with ALL smartphone heart rate software.

Of the many chest strap HRM’s on the market, the polar H7 is considered the benchmark in HRM accuracy. All the workouts and training logic for the CardioGuru fitness app have been tested with a medical grade ECG monitor and the Polar H7. The data reading of our tests (and by many others) show the H7 is very close to that of ECG readings, however the H7 (like all chest straps) tends to move frequently during weight training or High Intensity Training with movements like burgees, jumping and bag work. Women tend to find chest strap HRM's uncomfortable  and awkward to re-adjust mid training on the gym floor. 


My choice for a chest strap HRM "Polar H7"
Scott Alexander


Wrist Worn Fitness Tracker

These are the “IN” heart rate devices at this moment. Unlike traditional HRM’s, which are placed near the heart, the new breed of heart rate tracker use bioimpedance sensors that use light to measure pulse rate. What is appealable about this type of HRM is it is device practical, i.e. it is worn as a watch or fitness band, thus offering a “continuous” HR reading at any point of the day or night alongside a “fitness workout reading. This is useful for resting heart rate tests, to check recovery or to self-screen the sudden feeling of heart rate fluctuations/anxiety.

In short, wrist HRM’s work by shining light into the blood vessels of the wrist (blood absorbs light) the sensors can then detect changes in blood volume; the less light reflected back means higher blood volume, and from this a matrix formula equates the bpm.

What’s important to note here is that medical clinics have used “light” to measure pulse rate very accurately for some years, but this is only for resting heart rate. The more we move, so do our capillaries, tendons, muscles and the ambient light around us, thus making the light reading unstable. However arguably the market leaders in light sensor heart readings “ Mio Global” have developed algorithms that cancel out a lot of the "noise" generated by movements, and allow for the sensors to accurately measure heart rate at higher training intensity. If you look closely you will notice many of the brands that manufacture light HRM sensors do so under license from Mio Global.

Mio Global Alpha

I have used the Mio Global HRM for about a year now, and recommend the monitor to most of my clients. I have found the Mio to be very accurate as long as you are attentive to applying the Mio to the correct position on the wrist. Like all HRM’s the more you train under THRT protocols the better you become at stabilising your stroke volume, and this really helps with getting the most accurate reading as possible from the light sensors on the Mio Alpha (as a guide 2-3 weeks of 3-4 weekly sessions under THRT will create an adaption to more stabilised stroke volume).

The big plus however with the Mio Global is it’s very practical. Firstly it seamlessly connects via Bluetooth to the CardioGuru and all other fitness apps. I have also noted that my clients tend to wear their Mio Alpha watch on training days, and that has led to a very noticeable decrease in “I’ve forgotten my HRM” compared to having to pack separately a chest strap. This for me as a coach is a big plus.

The only area I can pick a slight flaw with the Mio Alpha is it shows signs of being less accurate in colder conditions, but when the body is warmed up it’s then fine. I therefore use the Mio as a good warm up marker, and will increase my warm up times until the reading is stable.

The other consideration to note here is that the Mio Global HRM does not present stable data for HRV readings. HRV (Heart rate variability) is an indicator of how well the parasympathetic nervous system functions. This metric reading does offer benefit in looking at recovery , training load and EPOC, but more so for advanced athletes who are probably best using an ECG.

There is also suggestion that bioimpedance sensors become less accurate with high intensity exercise. I use mine frequently on all my HIIT training and have solid data to accuracy,  I have also noted from my clients, that once they apply the correct approach to the placement of wearing an HRM, and have more stable stroke volume from the adaptation of targeted heart rate training, then more often than not an accurate bpm reading is obtained in HIIT, up until the point of "HR lag" where all HRM's begin to fail. Where the Mio Global does so well, its offering a more practical approach to wearing an HRM, and that means more people are beginning to think about training intensity and THRT. 

It’s worth mentioning the iWatch here too. Although it uses the same tech as the Mio, it has a different algorithm logic which I have found makes it very unstable. It takes a reading every ten mins which is not every useful. The big minus for the iWatch, although it can read your pulse, you can’t sync the live bpm feed with any other app par their own, so no HRM feed to other fitness apps i.e. the CardioGuru. I am not sure if Apple will change this, but this really limits the iWatch to nothing more than a bpm feed.


My 1st place HRM recommendation is the Mio Alpha
Scott Alexander 

Training HRM Limitations - HR Lag & Fatigue

I’ve discussed above that those not familiar with THRT should allow for an adaptation period so that they can better stabilize stroke volume during the varying of training intensity levels and obtain a more accurate and stable reading from an HRM. However there is another condition of training that can cause confusion as to the accuracy of a HRM reading.

Have you ever been in a HIIT session, whilst using a HRM and thought you're dam sure you are now working much harder as you move out of the rest zone into the push interval yet the heart rate reading from the HRM is showing no increase in bpm??..... But then as you decrease your intensity as you re enter you rest zone, your bpm suddenly jumps up?? Well you’ve just encountered “heart rate lag”, and the more unfit you are, and less experienced you are to THRH the greater and more frequent the HR lag will be during exercise.

On the first interval a heart rate response of 145 occurs after the interval has been completed - heart rate response lag.

Peak heart rate response occurs after the power effort is over on all intervals and on the last interval peak heart rate response climbed to 152 - heart rate drift upward. 

Power over each 60-second interval remained relatively constant which was the aim of the session

The confusion comes because when we apply power to an exercise we anticipate the same response like when we put the foot on the gas of a car, you expect an immediately responsive increase in the speedometer reading. If I am on the Wattbike and amp up the power, I will also see an immediate upward increase in my wattage output until fatigue sets in forcing a decrease in power output which will result in a decrease in the wattage being recorded in real time.

However at higher training intensities your heart rate may lag power. In fact heart rate cannot inform the intensity of physical loads performed above the speed/power of VO2 max in real time. There is a lag.

A further HR reading complication can occur during HIIT sessions with very short push intervals of 10-20s. At the exercise onset HR lag can result in a very much slower response compared with the VO2 response from effort. * Cerretelli - Cardiac output at the onset of exercise 

This means you could in fact be at the desired 90-95% HR Max from the training stimuli but fail to start applying the natural safeguard of withdrawing as to not to redline the interval (resulting in total exhaustion too early into the session).

Again learning how your body lags to heart rate, and under which conditions will help you select the workouts that you can achieve the most benefit from. As you begin to explore more advanced training methods, you will replace heart rate with "power i.e. watts" as the tracking metric for higher intensity based workouts.

Training Zones


The big advantage of using an HRM and monitoring your heart rate during training is that gives you accountability to training intensity and helps you avoid the big mistake of training “without purpose in the grey zone”. This means you avoid wasting time and energy on workouts that don’t deliver results. Training with an HRM with pre set training zones helps you achieve “training efficiency” and ultimately a “factual body response”. This is the winning formula athletes use.

Now there are many different training theories and approaches to setting training zones. The starting point is to establish a max heart rate and resting heart rate, alongside current baseline fitness ability, via fitness tests such as the Cooper Test, ramp test, or a metabolic test from a fitness-testing laboratory.

From this baseline you are then able to set training zones that will deliver session targets. For instance if electing predominately fat to fuel the session is the aim, then training intensity must sit under your AT (anaerobic threshold) and you may elect to train within your FatMax training zone, thus the use of an HRM ensures accuracy as to the session bpm which will help ensure your training intensity sits within the elected training zone.

Ultimately how you choose to set your training zones effects the effectiveness of using a heart rate monitor. This is where fitness apps and software fall short and is in part why I developed the CardioGuru Fitness App, which is the 1st real adaptive training tool in an app, and one that can accuretly set your training zones.

The logic behind the CardioGuru approach to training intensity and zone selection can be seen in the above picture.

Consider training zones as how you elect energy from the body to fuel a workout. Energy is essentially a chemical reaction from within the body which is either aerobic (occurring in the presence of oxygen) or anaerobic (without oxygen). We must continually produce energy or the tissues, cells and organs within our body will die. Now a specific amount of effort requires a given amount of energy, and the body must have an appropriate level of energy available to meet the demands placed on it. During FatMax zoned training you will be training under your AT meaning there be a regular supply of oxygen coming into your body, and as this continues your aerobic engine will fire up to provide the fuel (fat -> energy) to support the interval.

When you increase the training intensity to above 70-75% of your VO2 Max or above 85% of your Max HR this increase in training intensity will shut off the oxygen supply to the cells (forcing carbs to be used used as fuel) of the body, as it becomes unable to produce the required energy fast enough. This is turn forces the metabolism to “switch” into the anaerobic system so that these energy demands can be met. Training in the anaerobic threshold will spike post workout EPOC, which will require the body to burn more fat as it works to bring the metabolism back to it's rested state. 

Train Smarter 

HRM's are not yet perfect, but they are lot more accurate than just  "guessing" training intensity.  Inclusion of a heart rate monitor to your training gives the feedback that will enable you to push harder or dial it back depending on the training session goal and the fuel source the body will elect as energy.

You may be surprised by your heart rate reading during training, perceiving your exertion to be higher than your actual training output and this gives you the opportunity to push harder and smarter to achieving higher levels of performance........ 


#Focus On Performance, Aesthetics Will Follow