everything you need to know about heart rate

Heart Rate Training

Should I monitor my heart rate? Do I need a chest strap? What’s my max heart rate? What are training zones? If you’ve ever wondered the answer to these questions and more, this one’s for you. 

Let’s dive in…

Why monitor your heart rate (HR)? 

It provides you with a real time snapshot of your stress level, the intensity of your workout, your recovery status, your adaptation to exercise, your fatigue levels, your acclimation to the heat or cold, and your training status (overtraining). And of course, your cardiovascular response to exercise.

Your HR can tell you:

  • Correct intensity for aerobic or anaerobic system development
  • Correct durations for time spent in appropriate training zones
  • Appropriate recovery periods during interval training or between exercise sessions
  • Effective evaluation of adaptations to training programs
  • Early warning signs of overtraining, heat stress, & energy depletion
  • Race pace strategy for longer events

For more on heat stress, check out the post on Heart Rate & the Heat

What affects your HR?

As mentioned above, your HR can tell you a lot about yourself, but there are things that may affect it.

  • Sleep habits
  • Alcohol intake
  • Caffeine intake
  • Stress levels
  • Temperature
  • Certain medications – not just the obvious Cardiac Meds. If you take salbutamol (Ventolin) for asthma, that can create an acute increase in your HR when you exercise. The same thing can happen with cold & flu medication, arthritis medication, and antidepressants. 

Resting Heart Rate (RHR)

Quite simply – the number of times your heart beats when you’re at rest, measured in beats per minute (bpm).

Normal range range for adults: 60bpm – 100bpm.

Generally speaking, a lower RHR implies a higher level of cardiovascular fitness, and I love to use it as a non-aesthetic based fitness metric with clients.

There are some variables that affect your resting heart rate:

Modifiable factors:

  • Smoking status (incl. marijuana & vaping)
  • Stress levels
  • Lack of sleep
  • Obesity
  • Frequent binge drinking
  • Caffeine
  • Fitness level

Non-modifiable factors:

  • Sex: Females tend to have a slightly higher RHR than males (2-7bpm)
  • Genetics: There is some genetic predisposition affecting our heart function

The size of your heart also plays a role here, as a larger heart can pump more blood out with each beat (this is called Stroke Volume) and therefore doesn’t need to beat as often. 

Elevated RHR

An elevated RHR indicates that your heart may not be working efficiently, and is a predictor of cardiovascular disease. If your RHR is continually above 80bpm, it is worth getting checked out by your medical provider. You can start by looking at what modifiable factors apply to you.

How to measure RHR

  • First thing in the morning after you’ve woken up is the best time to measure.
  • Using 2 fingers on the inside of your wrist, you’ll usually find it between the tendon and bone.
  • Don’t take it at your neck, pressure on the carotid artery can slow your HR down, causing an inaccurate measure.
  • Keep a diary and use the week’s average due to the day to day fluctuations we have. Eg you may see a higher resting heart rate the day after a high intensity work out or if you are sick.

If you have a smartwatch, it will usually have a RHR measure. This will be shown on the watch itself, as well as within the app. Keep in mind that this will be most accurate if you wear it to bed as well a throughout the day.

A screenshot from Garmin Connect showing resting heart rate
Resting heart rate in Garmin Connect

Max Heart Rate (MHR)

We’ve all seen those charts at the gym or on cardio equipment telling you what your MHR should be based on your age using the formula HRmax = 220 – age. Now here’s the interesting thing: that was devised in the 1930’s and not developed form original research, rather the observation of data from other references, some of which were unpublished. 

There have been many formulas devised since, but heart rate is very individual and age-based formulas usually have a large prediction error of >10bpm. Many factors determine your max heart rate including age, ethnicity, sex, genetics, training status, and body composition.

Many fitness trackers estimate our MHR based off our age, and use this to prescribe HR training zones. This data is used to provide performance metrics such as training status, training effect, lactate threshold estimate, and VO2max prediction.

If you are interested in finding out your true MHR, in lieu of an expensive lab test, there is an easy ‘field test’ that you can try as recommended by Benson & Connolly.

  1. Find a 400m running track, or a small & gradual incline 400-600m long
  2. After an adequate warm up, run one lap or incline as fast as you can then record your HR when you have finished
  3. Take a 2 minute active recovery – walking for jogging – then repeat the effort and record your HR
  4. Your HR at the end of the third effort will be a pretty good prediction of your MHR

You can try a fourth effort if you feel you haven’t reached your max. Once you have this number, you can edit your MHR in your fitness tracker and your training zones will be recalculated based off this new number. 

*NOTE: If trying this field test, make sure that you don’t stop entirely after the max effort, walk a few laps to cool down. It is assumed that you are physically fit and well enough to try this test, and have been cleared by a physician if need be.

Heart Rate Zones

So now that we now how to calculate our max heart rate, we can use that to find our training zones. If you have a smart watch, it will calculate for you when you enter your MHR.

a screenshot of heart rate zones in Garmin Connect
Here’s an example of heart rate zones from my Garmin, shown in Garmin Connect.

Zone 1: 50-60% of MHR

  • Easy & relaxed pace
  • Easily able to carry on a conversation
  • RPE 1 (0-10 scale)
  • Warm up zone

Zone 2: 60-70% of MHR

  • Comfortable/easy pace
  • Breathing rate has increased but you can still hold a conversation
  • Ideally, your long slow runs are in Zone 2. This can take some practice!
  • Zone 2 training builds our aerobic base

Zone 3: 70-80% of MHR

  • Moderate pace
  • Can still speak, but in shorter sentences
  • Whilst still considered aerobic, there is some lactate response which impacts recovery
  • Too hard to be considered easy, but too easy to get any desired benefit
  • If you feel like you have plateaued in your running, you’re probably hanging out in Zone 3 too often

Zone 4: 80-90% of MHR

  • Threshold pace, anaerobic
  • We’re getting pretty uncomfortable and are down to 1-2 word sentences
  • Your tempo runs will be in zone 4
  • Zone 4 improves our lactate threshold. Basically, this is your ability to work harder (higher HR) for longer

Zone 5: 90-100% of MHR

  • This is your maximum, all out!
  • You have no interest in trying to speak
  • Unable to sustain for a long period, your muscles are using oxygen quicker than you can suck it in
  • Sprint efforts

Wrist based monitors have come a long way, but a chest strap is still the most accurate way to measure. And the data is somewhat useless if it’s inaccurate. I highly recommend investing in a chest strap

If you’re spending a good chunk of time in zone 5 with a chest strap, I would question whether your MHR is accurate. In place of a lab test, try one of the field tests from last week and adjust if needed

Long Slow Day (LSD) runs in zone 2 may seem impossible. Patience, practice, you will get there!

Heart Rate Variability (HRV)

HRV is the variation in time between heart beats. This is measured as the R-R interval on an ECG. HRV is scored on a 0-100 scale.

First, some physiology

The Autonomic nervous system regulates bodily functions that include respiratory rate, blood pressure, heart rate, and heart rate variability. There are two divisions of the Autonomic nervous system – Sympathetic and Parasympathetic

  • Sympathetic = fight or flight response
  • Parasympathetic = rest & digest

A high HRV is indicated by a wide variation in R-R intervals. This means there is a healthy balance between the sympathetic and parasympathetic nervous systems.

This is referred to as “Autonomic Balance”.

A higher HRV score (greater variation in R-R intervals) reflects greater cardiovascular health, a higher level of fitness, and increased ability to adapt to workloads and stress.

A lower HRV score reflects poor cardiovascular health, a lower level of fitness, and poor ability to adapt to stress.

Average HRV is around 60, but it will decline with age.

Your HRV will change daily with your training workload. As with many things, it’s best to take a weekly average.

Measuring it daily can give you a good indication on your body’s recovery status. If you haven’t fully recovered from a hard effort the day before, it will be lower. You can use this to guide your training and avoid overtraining.

Some smart watches collect HRV data to calculate different performance stats. Eg Garmin’s training status feature.

Low HRV is an independent risk factor for cardiovascular conditions such as hypertension, heart disease and heart failure. Decreased levels of physical activity will lower your HRV

But regular aerobic exercise will increase it! The current ACSM guidelines are at least 150 minutes of moderate to vigorous aerobic activity each week.

How to measure?

You’ll need a chest strap that is bluetooth enabled. Some Garmin models have a HRV test that you can add as an activity. I’m sure other brands may have something similar. 

EliteHRV – download the free app and connect your chest strap.

Chest Strap Monitors:

A chest strap monitor measures the electrical activity of your heart beat, similar to that obtained by an electrocardiogram (ECG). The chest strap is the transmitter, and sends the data to your watch, which is the receiver. 

The main pro of using a chest strap is that it is the most accurate measurement of your HR without an actual ECG. 

Accuracy is important if you:

  • Use your HR to guide intervals
  • Use your HR to guide recovery
  • Use performance metrics on your watch such as training status, training effect, lactate threshold estimate, & VO2max prediction

There are some cons to a chest strap monitor. It is usually an added cost on top of the cost of your watch. Prices range between $60 and $200 depending how fancy you want to get. You can get ones specific for swimming, ones with extra running dynamics, or even ones that display your HR on your phone and don’t need a watch to pair with.

Some people find chest straps uncomfortable to wear – it must be tight enough to get an accurate reading, you don’t want it to be slipping around during your workout. Some synthetic t-shirt materials can affect the accuracy by producing static when it rubs over the sensor during your workout. 

Wrist Based Monitors:

Wrist based monitors take an optical measurement using a light diode (photoplethysmography). This measures pulsatile blood flow through the skin by sensing the density of your red blood cells as they pass under the watch.

Wrist based monitors are cost effective as they are included with most fitness watches these days. You don’t have to purchase, or wear, anything extra and you can choose to have it reading your HR continuously, or just during activities. The later will help to extend the battery life of your device. 

The major con of a wrist based monitor is that is far less accurate. You need a higher-end model to increase the accuracy and these can be quite expensive. There are also many factors that can increase the inaccuracy of the wrist based monitor:

  • Motion artifact eg the watch strap not done up tightly enough. If your watch is too loose, you will generally see a lower HR recorded
  • Skin tone
  • Tattoos on the wrist
  • Ambient light
  • Edema
  • Poor circulation

Heart Rate Recovery

Heart rate recovery is another tool in our belt that reflects our cardiovascular fitness. It is essentially the ability of our heart to recover from a bout of exercise within a specified time period (usually 1-3 minutes).

The quick decrease in HR is our Autonomic nervous system quickly shifting from sympathetic to parasympathetic. Therefore, heart rate recovery is a good indication of Autonomic Balance.

Research suggests that poor heart rate recovery may increase the risk of future cardiovascular events and early mortality.

Acute HR recovery:

This is immediately following your activity. The ability for your heart rate to recover after an effort indicates a higher level of cardiovascular fitness.

You want to see at least a 20-30bpm drop after a 2 minute period. Garmin recommends consulting a physician if you are consistently seeing a drop of <12bpm after 1 minute.

You can measure this yourself by checking your heart rate at the end of your activity, and rechecking it again after 2 minutes. Subtract the second HR from the first and that is your HR recovery.

NOTE. Acute HR recovery is only really valuable after hard efforts. You shouldn’t see a 20bpm drop after a walk or a yoga class.

Many smartwatches have this feature built in, as is shown here on my Garmin.

Some models will show this on the screen automatically after an activity has been paused for 2 minutes.

On others you can scroll down to “Recovery HR’’ after pausing your activity and the timer will begin.

a picture of a Garmin watch face showing a recovery heart rate of 44 beats per minute.

Long term monitoring:

As mentioned above, you may see an increase in your RHR in the day(s) after a hard effort. As your fitness level increases, this difference will not be as pronounced as your HR is able to recover more quickly.

Do you monitor your heart rate? If yes, do you use a chest strap or a wrist based monitor?

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📚References:

  • PMID: 30365812
  • PMID: 23913510
  • PMID: 20585008
  • PMID: 29599724
  • PMID: 20585008
  • Benson R, Connoly D, (2020) Heart Rate Training (2nd edition) Human Kinetics
  • ACSM’s Guidelines for Exercise Testing & Prescription, 11th edition
  • Powers & Howley, Exercise Physiology, 8th edition
  • www.garminfitness.com

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