Heart Rate? Heart Rate Zones? What's it all mean?

Heart Rate 101 - Keeping it simple and useful

I'm going to try and keep this as simple as possible. There is a lot of information available online, but hopefully this post provides a starting point and my personal perspective on the topic.

What is it? The heart is a muscle that pumps blood to the body. Like all muscles, it can be trained and improved, but it can also be over trained and stressed, which is why it's a good indicator of exercise effort. The heart rate is the number of times the heart beats in a minute and the unit of measure is "beats per minute" or "bpm". For example: 60bpm.

How is it measured? There are variety of ways heart rate can be measured. Heart rate can be taken:

• Manually by counting the number of heart beats in one minute, from a pulse on your body (e.g neck, or wrist),
• a heart rate monitor strap across the chest,
• a heart rate monitor on your wrist watch,
• or an app on your phone (by placing finger on the camera lens).

When is it taken? There are a few times when heart rates can be taken:

• At rest, also known as "Resting Heart Rate".  This is is the number of heart beats in one minute when you are resting, sitting, or lying down. The best time to take this is immediately once you wake up, as you're free from environmental stimulants. Generally, Resting Heart Rate provides an insight into an individuals fitness as it means their heart is more efficient (able to pump the same volume of blood with less pumps per minute). For example, an individual with a Resting Heart Rate of 40bpm could be considered a well trained athlete.

The results of my resting heart rate that I capture each morning on my mobile phone app.

• At different times during exercise depending on the purpose. For example, "Average Heart Rate" for the exercise duration, "Maximum Heart Rate" during exercise, or even post exercise "Recovery Heart Rate" that gives insight into how quickly the heart can return to its normal rhythm. As with all data, it can helpful or create more confusion and noise (as the old saying goes, paralysis by analysis). Personally, I like to review which zone my heart is operating in during a given set of exercises, and monitor for changes over time against the same set of exercises. 

What are Heart Rate Zones?

This is where it starts to become more confusing. There are a number of different ways to calculate your Heart Rate Zone, and "experts" use different labels to classify each zone. Things to consider:

• I see Heart Rate Zones like a stress gauge for the heart. It provides a graphical representation of the effort made by your heart to supply blood to the body during exercise.
• Heart Rate Zones are unique to an individual. To calculate Heart Rate Zones, your Resting Heart Rate, Maximum Heart Rate or age will be required depending on what the formula requires.
• Karvonen, Age Adjusted, Leger, Friel, Zoladz are all different methods to calculate your Heart Rate Zones. From what I've seen, Karvonen seems to be the most popular, however this a personal preference. The key point is to keep the way you calculate the zones consistent so you can compare your results properly.
• Once you have your Heart Rate Zones calculated, you'll notice that each zone can be labelled differently depending on the source of your information. Most basic is Zone 1 to Zone 5, sometimes even to Zone 7. Some may use terms like; Fat Burning/Cardio zone, or Aerobic/Anaerobic, or Tempo/Threshold zone. Terminology or the labels are not important. As long as you understand the corresponding heart rates for each zone, and what zone you want to operate in for your specific exercise that's the most important part. For example, as part of my 14 week marathon plan, I'm monitoring my heart rate to see how often my heart rate is in Zone 4. Zone 4 is often considered a Hard/Anaerobic/Threshold zone, and not a zone I want to have my heart operating in for the duration of a 3 hour marathon. So I will be monitoring if my heart rate will spend more time in Zone 3 as the training progresses week by week. If not, I'll have to revise my goal pace to be slower.

Final notes about Heart Rate

Although measuring heart rate can be extremely useful, it can also be impacted by external factors. So it's important to note that whilst it is a good indicator, it is NOT a precise one. The following list are some examples that can influence your heart rate (increase beats per minute):

• Heat and humidity,
• altitude,
• being sick
• taking caffeine, or stimulants,
• feeling stressed, angry, anxious, or nervous

There have been some new advances in measuring and reporting Heart Rate measurements and  information. These include the ability to provide Heart Rate Variability (HRV) and VO2 Max calculations. HRV can be useful to understand the condition of the heart; is it over trained and therefore need to rest today, or can I push harder today etc. I'm currently trialling this and will report back once I have enough data to share. Stay tuned.